Hi !

So I'm the owner of a volvo 245 with a B20A engine and a M40 gearbox.

Since in europe the temperatures a getting below freezing, I ordered a new thermostat (quality brand). The thermostat is rated at 88°C.
Until now, the thermostat installed in the car was modified to be always open.

So, I installed the new thermostat, put the expension thank as high as possible and started the car. Meanwhile I was pressing on both radiator hoses.

My problem: the car is getting hot very fast. I know the thermostat opens because I tested it in boiling water and it was fine.

If I drive the car, I have hot air in the cabin. But the needle of the temp gauge is always in the hot area.

The top hose of the rad is hot but the liquid in the expension thank is cold. The lower radiator hose is also cold (same for the radiator)

To be honest, I don't know what's wrong... Radiator blocked ? Bad/old coolant ?Before the car was working fine with the open thermostat. Maybe the coolant temp sensor is bad but it's not normal to have only one hose that is hot.

Thanks for your inputs because I'm a bit lost :)

Regards from Switzerland.
Nanan

So, here's a big update !

I did multiple flushes, heater core alone, the engine, with and without the garden hose. I got some of the "rusty sand" out but there's still some.

I also swapped my 88°C thermostat for a 76°C. Now the needle is showing just above the normal temperature. That's reassuring because, the engine is not overheating :)

However, I still have to keep flushing the cooling system to get more rust out. Now the temperature is fine, because it's cold outside, but this summer I will have problems.

So, I think we can consider this case resolved !

To sum up my problem and solution for future readers:
Got a 245 with a B20A engine, the thermostat was removed meaning the car was not warming up (not an issue for summer, but during winter this was an issue). I installed a 88°C thermostat and the car started overheating (even if I bleed the system correctly).
I checked if my radiator was blocked, check if my coolant temp. sensor was faulty, installed a new style voltage stabilizer for the gas and temp. needles in the cluster. All of this with no improvement.

I finally did a full bleeding and found some brown sand in the coolant, I did multiple flushes and installed another thermostat (76°C) and now the car seems to be fine. But I still have work to do in order to remove more of the rust inside.

In short, make sure to bleed you cooling system from time to time and use distilled water !

Thanks to all the people that took the time to read me and helped me throughout the diagnosis.

Regards,
Tobias

My guess is--if you remove the exhaust manifold to gain access to the freeze plugs and then remove the discs and you'll find the water jacket filled with rust--probably right up to the opening. - Dave

Yep, I think you're right.

I was thinking of removing the head from the car in order to send it to a machine shop for adapt it to unleaded fuel.

When the head is off, I will remove the freeze plugs and clean everything !

Update !

Thanks for everyone that answered ! Thanks for sharing your knowledge and remarks about my issue.

I would like to make a recap like this everyone is a the same page:

Got the car recently, the car was not going into temperature so I ordered a new thermostat (88°C) and installed it. Since, the car is indicating a high coolant temperature.
What I have done so far without improvment:
New rad and hoses, new coolant temp sensor, installed a new voltage stabilizer behind the dash. I check the cooling tube in the cylinder head and nothing is blocked.

However, while everything was apart, I remarked that there is some build-up in the coolant galeries of the engine, it's brown and some particules are magnetic. I assume it's rust. With the thermostat out, I decided to clean as much as i could but there is still much more to do.

So now, my hypothesis is the following: There is a flow issue due to partially clogged coolant galeries in the engine. I will replace the water pump anyway and while this one is out, I will be able to clean some galeries even more.
In the meantime, I will do multiple coolant flush until the water is not brown anymore. Maybe I will check if there is a product that I can add to clean my cooling system a little bit.

If you have any idea / input it's welcome !

Thanks for your time and your help !

While you have the water pump removed to carry the engine flush, why would you not remove the temperature sensor and flush that cavity with a presurised garden hose ?

Then inspect that cavity and make sure to remove any crust so that coolant moves in that area.

This is what I would do.

Hi Roland, good post!

I might add a thought on yours that he can try back flushing by also removing the heater hose that comes directly out of the block.

Since he will have the hose off he can flush the heater core.

I suspect that the previous owner did not antifreeze or double oil to prevent rusting.
With his inspection with the water pump out he can observe and scrape the bottom of the cylinders water jackets for fallen flakes.

He asked ....?
I’m hesitant to say that you can use this product with the head on as it might not work with aluminum in contact.
You will have to research this product before using it in your engine block.
I figure you can block off the water pump hole and only fill it up half way if the stuff doesn’t like aluminum. I think they don’t recommend the use of it in a galvanized container?
I just don’t recall all the conditions but it works against cast iron or any steel rust!
Aluminum doesn’t rust, it corrodes!

The product that I got at the hardware store than chemically converts rust to actual remove it.
It will save tools you get cheap from garage sales!
It’s called “Evapo-Rust.”
It has gotten more popular and even Walmart carries it on line by the gallon.
I will add the price went down too from where I first used it to clean out an “air conditioning”condenser.

I felt it was a really a safe cleaner! I have used a lot worse things in my life!
What the bottle claims is true to me!
I still used precautions to make sure it was out of the “system” with plenty of rinsing with other solvents, to remove water, due to it being an air conditioning system. Water is a big no-no with refrigeration.

The condenser got rusted on the inside from the previous owner getting “wet” R12 put in.
I’m sure some boot leg or black market R-12 was used.
I bet she never knew it like me!
I too, bought the car used, like him, so he will have to be aware that its no telling how long it was rusting.
Mine worked fine for 13 years before it got a clogged expansion orifice.

Something to consider if he thinks the rust is outrageous!

Phil

You're right !

I haven't though of it.

Thanks !!

I have found thick deposits of rust/muck in the cooling jackets surrounding the cylinders on a couple of motors. Unfortunately that requires removing the freeze plugs under the exhaust manifold to dig it out. - Dave

Could the engine be a substitute for the original engine and there is a mismatch between the temperature sender and the gauge?

Nanan - after reading all the posts up to Dec22 - here's what I would do.

This does not cost you anything.

1. Pinch off the hose to the expansion tank.

2. Use a turkey baster or other large suction device and lower the water level in the radiator about 1 and 1/2 inches.

3. leave the radiator cap off and warm the car up until the gauge reads hot. (Do this outside in case the radiator overflows.)

4. Measure the water temperature.

As suggested, the temperature gauge or sender may be defective.

The first time I drove my '64 544 with a B20 engine in a parade I could not believe how hot the temperature gauge became. I had bottled water on board and threw some into the radiator. The car did not steam or show any signs of overheating. This was a special parade and took an hour! I was on pins and needles the whole time

I later found that the gauge was hyper sensitive and went to normal quickly as soon as I picked up speed.The gauge would even go up a bit when I stopped for a traffic light.

If you want to see Beetlebomb (that is a song on youtube) in that parade - search brick pix for 544s and go to page 6 - March 12th, 2006. He is in his fire department costume.

Hi,

Thanks for your feedback.

@Roland: I did have a look at the 140 forum, read the thread but nothing got out of it.

@James: I unfortunately don't have a radiator cap.

I bought a infrared thermometer and did some measurement (outside temp 10°C / 50°F):

After 5min of driving (needle way past the red mark),
-the hoses going to the heater core were about 45°C (113°F)
-Top of the rad around 30°C (86°F)
-Thermostat housing around 45°C (113°F)
-Bottom rad hose 18°C (64°F)

After 15min of driving at 50km/h (30 mph):
-the hoses going to the heater core were about 65°C (149°F)
-Top of the rad around 50°C (122°F)
-Thermostat housing around 80°C (176°F)
-Bottom rad hose 30°C (86°F)

Maybe my water pump is not moving enough water ?

Hello to everyone !

I've read your answers and will reply to them one by one.

@Roland: Yes, we have the same understanding of this cooling system. I too think that the cooling is fine in this car, this is more gauge related.

About the voltage stabiliser, after some researches, some say that there is one at the back of my cluster and some others say that's a big metal box under the hood.
I assume that the one that may cause some issues for my problem is the one at the back of my cluster ? I also want to point out that my fuel gauge is working.

@Nahtanha: Also possible, I think I will change the water pump if I don't find anything obvious. But someone changed it before me because it's still shiny but I will swap a new one for good measure.

@CeeBee: If I understood well what you said, for you there is not enough hot water flowing through the rad in order to cool the system. Which tends to indicate a bad water pump ?

Thanks for your help !
I wish to everyone happy holidays.

Brings to mind my HS Chemistry teacher(I'd call him a Prof), who introduced us to AboGabo's Number: 6.02 X 10 to the 23rd. How's that for Teaching (HS Chem - 1966)

So dear Nanan- 212deg F is the Boiling Point of Water. 100deg C.

If it were not for the 'Coolant Mixture' that not only lowers the Freeze point ---but also Raises the Boil Point...you would have stewed neather parts, thanks to your bursting heater core and associated hoses---inside the cabin.

Cheers

Thank you very much for your explanation.

Ok, I get it. I have just one stupid question: Since the temp. sensor is screwed in the head, the sensor should be hotter than the coolant because there is heat transfer from the head to the sensor ? I don't know if what I'm saying is clear or not :)

Hi,

I enjoy seeing this as a good sign of you being inquisitive and that by itself helps "us" on the BrickBoard so our brains don't go stale!

I think I understand what you are asking and will give you credit for thinking about the heat transfer.
The thoughts that you are processing with has a couple major flaws. The transfer capacity of the coolant over the aluminum and the location of the sensor must be considered.

The physics of our coolant is made of water and that will surpass the rate of BTU's conductivity capabilities of metals per pound. Very efficient when compared to our other refrigerants.
Water is the best refrigerant and in lots of cases it is considered a universal solvent in natural events.

Hydrogen gas is the next best coolant so if figures to be that, as it's in water too!
Heavy water is not natural but plays off hydrogen's unique qualities.
This leads to the Universal question ...
You can burn oxygen and hydrogen separately but so far, not together? I guess the combination zaps the heat energy somehow. Maybe for the lack of densities or too much?? The sun works!

The sensor is located "low" in the coolant jacket.
The thermostat is up at the top for the head for reasons that the heat spreads molecules apart and "expansion" occurs.
This activity in density change by volume is controlled by a coolant recovery bottle. It is used to keep air from entering or staying in a cooling system.
The theory is, where there is an air bubble, there will be a lack of water next to the water jacket in the block and the cylinder head. Air conducts less heat than the fluid.

The sensor only has contact with the head through its "V" shaped threads. The actual heat contact is only on the sides of that V shape. So consequently, the brass tip and its sensor material is not up inside the body but extended out into the coolant flow.

So, this was not a stupid question, as I have seen quite a few of these thoughts over the years on the BrickBoard.

Thanks

Phil

If you haven't already, I suggest pointing your IR thermometer at or near the water temperature sensor at the back of the cylinder head.


--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

I did it, and the sensor itself is around 212°F after 30min of highway driving.

I took apart the voltage regulator at the back of my cluster and the inside is shut. The coil is becoming dust when I touch it.

I ordered a replacement voltage regulator. Will keep you updated along the way.

212° is too high. The temperature back there should be closer to the temperature of the thermostat being used.

Was there any silicone sealant used to seal the thermostat housing or water pump?

If there was you may have accidentally plugged the small openings in the brass tube inside the cylinder head while removing the old silicone when you installed the new thermostat.

This tube is concealed behind 1 of the 2 small core plugs on the front of the cylinder head and can be removed for cleaning. The tube has small openings that direct cooled water into the block and those holes can easily be plugged by debris like pieces of silicone sealant.


--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Hi,

What you're saying is interesting because when I removed the old thermostat (which only he part holding the rubber seal was left) a bit of sealant was around the rubber seal. That's possible that when I removed it a bit went into the brass tube. I think since the thermostat was removed by one of the previous owner, it may have been plugged before by sealant or rust particules.

However, I don't know of sealant was used for the water pump.

Now, at the front of the cylinder head, between the thermostat and the water pump are two plug (I guess around 29mm) I should remove both of these see behind which one these is a this brass tube ?

Thanks for your help.

Hello,

The long brass tube is behind the plug on the right when you are looking at the engine from the front.

The size of the plug is 35mm and it is not the normal style of plug.

Volvo used Welch plugs or sometimes called disc plugs.

To remove any of the Welch plugs in the cylinder head or engine block EXCEPT FOR THE 4 PLUGS ON THE EXHAUST SIDE OF THE ENGINE, use a long handled punch with a sharp tip in the center of the plug and a hammer the punch straight in. Once you have about an inch of the punch inside you should be able to pry the plug out with the punch.

To avoid possible damage to the outside of the cylinders, the removal procedure for the 4 plugs on the exhaust side is slightly different. You want to place the punch off center and make a dent straight in, then using the dent as a starter, point the punch at an angle away from the center of the plug. You don't want to be too close to the outer edge either as there is a stop ring cast into the block to keep the plugs from falling inside and you don't want to break that.

To install a plug, 1st you want to thoroughly clean the inside of the opening in the block paying close attention to the sides of the openings especially near the stop ring as the plugs seal on the sides of the openings.

Coat the edge of the plug with a thin amount of sealant, preferably not silicone. We use a product made by Permatex and its called "2".

Then push the plug into the hole and make sure the plug is fully seated against the stop ring. I like to take a socket and hammer and tap gently on the socket as I move it around the outer edge of the plug to confirm that I got the plug to seat properly.

Now comes the tricky part, you need to deform the center of the plug. We use an appropriate sized socket for the size of the plug. We use a 9/16" socket for the 35mm plug. You can use the other installed plug to compare your installation.

--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

You wote:

After 15min of driving at 50km/h (30 mph):
-the hoses going to the heater core were about 65°C (149°F)
-Top of the rad around 50°C (122°F)
-Thermostat housing around 80°C (176°F)
-Bottom rad hose 30°C (86°F)

Ergo... Cogito ergo sum.
(BICE - Before the Internal Cumbustion Engine.)

The Mojo ain't comin' Thru the Rad.
If it ain't comin' thru the Rad
It Ain't COOL'in
Much

Just a tiny bit...since You ain't boiling over.

get me hep cat??


Take an Aspirin Taab then..

call me when it's 95 like in the summer---

If your car has been sitting for some time, the metal impeller blades of your water pump could be rusted away in some area. Some of the water ports inside the water pump housing clogged.

I should explain how I understand the cooling system of the B20 and B230 engines.

1 - The water pump circulates cooling liquid in a closed loop inside the engine when it is cold. At this point the thermostat is closed. Notting goes to the radiator but the heater get some liquid flowing in if the heater control is open.

2- The pump reciculate part of cooling liquid when engine is warm at operating condition. At this point the thermostat let overheated liquid out to control the designed temperature (say 88°C). It will open just enough to keep the engine warm, and will fully open if the temperature exceed say 4 or 5°C of your thermostat.

In other words, with engine at normal temperature, the cooling liquid at the hose close to the thermostat will always be around 88°C. The volume will be more or less depending how much work the engine is doing.

So at operating temperature it is normal that the upper hose be hot all the time and bottom hose cold. A good condition radiator will have a warm or cold bottom hose. I assume you know your water pump is in good condition. I have never seen a loose impeller but it could happen.

Do not forget that the water pump is getting part of its liquid from the radiator and part of the engine block. If you look under the thermostat you will see the center hole that let the cooling liquid go to the pump. As the thermostat open it does block that center hole more or less to keep the engine temperature at 88°C.

Thermostat housing at 80°C is normal as you are measuring on the outside of the aluminum head. And if your instrument is in the red it is defective.

If you replaced the sensor then you will have to follow the wiring to the instrument cluster.

In the 140-160 forum is is mentioned that a gage showing faulty high temperature on a 140 may be caused by a defective voltage oscillator. Again your instrument cluster may be different than the 140s and I don't know these and cant help you on this. My 1982 has a voltage regulator.

I would suggest you look at the 140-160 forum right now as there is a temperature diagnosis question. It might help you fix the temperature reading problem you have.

These cars have the B18 and B20 engine and have a different cooling system than the B230. Volvo 240 1975 was the last year B20 engine was used.

Do not forget to reply to us in the 240 forum as there are many of us watching and trying to help.

Best wishes to every one.

I've read all the responses and would have to agree--either the radiator is blocked or the thermostat is defective despite your boiling water test. I have a couple of good 240 radiators. If you are in the NY metro area you can "borrow" one for a test. I live on Long Island one hour from Manhattan. - Dave

Nanan is in Switzerland so I guess this option is out. Did they keep a 140 type rad for the B20 engined 240? The change to the B21 may have needed a different one with different inlet and out positions. What do you say Nanan?

Hi,

first of all, I would like to thank everyone for taking the time to read my problem and give an answer. I really appreciate that :)

About the issue, I ordered a new rad, expension tank, rad hoses. I will install everyting this week end (if the parts show up on time).

For me the rad is very likely to be at fault even though I don't get how it is possible that with just a new thermostat the fault is showing.

If with a new rad, the problem is still present I will order a new thermostat and investigate further.

While waiting for the parts, I'll put the old thermostat back and see the issue is still the same (the goal is to rule out the "trapped air" possibility). Maybe I hurt the engine when if was running hot (even if I had the heat on full and it was heating the cabin really well).

You may have guess that I'm new to this car, I only own it for a few months now and starting find out issues that were not solved yet. But really happy to drive this car :)

Thank you, I'm happy to join a community were people are that nice :)

Hi,

How old is the water pump?

The top hose should always be hot since hotter water is less dense and will rise to the top of the system along with air, but that, will eventually “burp itself out”the expansion tank cap.
The bottom hose should be cooler by 30 degrees as a rule of thumb after a good time to normalize all components.

Are you using a thermometer or judging this by hand?
Maybe it’s just trickling around and through?
Maybe the impeller in the pump is loose on the shaft, rare, or has been eaten away, if it’s the original one? How many mikes are on this reliable long working steed, anyway?

You say you have heat in the cabin, when you drive it? That’s a statement to consider for variations on.
How about the rest of the time? Is it intermittent that it works good and then fades away.
A really soft bottom hose can collapse and cause a restriction.
I have never experienced that on a Volvos but on larger engines have wire springs inside their hoses.

I sure hope you have changed out the radiator and pump over all these years!
Lots of time the fins themselves rot away from the tubes from corrosion, especially, if it resided along a salt water coasts and snow cleared highways.
If distilled water was not used, things might be thick with rocks in the radiator or problems around the cooling jackets of the engine.
Rust in the block occurs if the antifreeze was not maintained regularly. If the heater is inside drops the needle, then one would assume it’s the radiator, outside.
But I would not pass on the impeller of the pump not being efficient enough except at speed.

Since you are new to owning this car you are correct in the expectations of “the not so good!”


As far as the gauge sensor being bad is always a possibility!
This includes the wiring harness to and from it.
The USA 1978 models are know to end up with a wire going bare of insulation.

Does it go up gradually as the engine warms up?
You say it’s quick, how quickly?
It’s got to take several minutes normally depending on what you start out with.
Did your “quality made thermostat” tell you to put in thermostat wiggling vent valve upwards, towards the top?
It helps pass air and a trickle of flow through the head during warmups.
I like WAHLER 92 C for emissions and holding the engine warmer between startups myself.
Even though they have changed out owners, they are made of brass and copper. A more closely made mix of similar metals to me. The Swiss have known about making good metals!
I have had them to last for years and years, worth the 15% more in cost, IMHO.
A 87 or 89 keeps the needle slightly below mid range of normal where the 92 gets mine straight across on all of my later 240’s. 1978-1993!

It look like you are on the right path to saving the life of this car!

Phil

It seems your post hit the same time as mine.

for what it's worth---don't know where you are located---

But--- if you have the original All Metal Volvo radiator and have a Radiator shop nearby...there are things you can do.

The Radiator shop can: Flow test the radiator. They can do a 'Hot Flush'.
They can Ream/Rod the core. Or Re-core.

You may want to put the new radiator purchase on hold until you price these options.

Then again, maybe I'm living in the late 20th Century and these services and shops no longer exist...You just toss it out and replace with new -plastic.

good luck

same radiator---My 1975 w/B20, 1980 w/B21, 1987 w/B230. entire 240 line same radiator.

However:
the older ones...are all metal and can be reamed/rodded by a competent radiator shop.
The older ones can also be Re-Cored --- If you can find a shop that can do a re-core.

All the newer ones are Plastic tops and bottoms with aluminium cores and must be tossed when they leak.

How old is the radiator? Why was the old thermostat removed?

I don't know how old is the rad, I assume it's original.

I don't know why the thermostat was removed... Maybe they didn't want to change for a new one.. Or it was to avoid to replace the rad.

Sorry for the lack of information.

I had a 1975 245 ---same as yours but the US model so it was KJet FI, not carbed.

If you had flow thru the radiator sufficient to run the engine, as you said too cold, that would indicate that there is plenty of flow.

What is perplexing is that by adding a functioning thermostat, you basically cut the flow to Zero. Since the lower hose remains cold as well as the radiator.

First thing you should do is confirm that your install of the thermostat is done correctly. You only have to drain off a small amount of coolant to drop the level below the thermostat housing and inspect your install.

My guess is that there is air in the system.

Here is a trick to try while you have the thermostat exposed. Get a sugar cube, wedge a piece of it so the thermostat is held Open. This will let you get all the air out of the system and none will get trapped behind the thermostat when you re-fill with coolant.

Run the engine with the Cap Off the expansion tank. When you feel the lower radiator hose start to warm up you can put the cap back on.

So:

1) Lower coolant level a bit. You can do this using that Drain Cock at the rear of the Block under the exhaust. Attach a rubber hose and catch it in a bucket.
When the level in the expansion tank drains down --- that's plenty.

2) Open up the thermostat housing. Check your Install. Wedge a small chunk of sugar cube forcing the thermostat Open.

Button it all back-up. Add the coolant back. With the Cap Off the expansion tank...Start the engine. The coolant will circulate freely

The coolant will dissolve the sugar cube.

There should be zero air in the system.

Run it until the engine warms up to operating temp, and the thermostat opens on its own.

Thanks for your message !

I'm in the same boat, before the car was only getting hot in rare occasion is the car was kept running (for a while) without moving, but as soon as I was driving it got back to "too cold". But that does not explain why the previous owner removed the thermostat. In another hand, by adding a new thermostat the rad is 100% blocked...

When I first changed my thermostat, I only drained the expension thank with a syringe and unplugged the top rad hose into a bucket. That was enough too removed the thermostat without making a mess.

My thermostat has a "jiggle valve" that allows the air to escape with the thermostat opening.
In order to stuck the piece of sugar, I need to put the thermostat in boiling water beforehand don't I ?

Thanks

If your new t'stat is working properly, as you observed with the pot of hot water, it is NOT the source of the blockage. And if the jiggly air bleed is present, then air pockets are not the likely source of overheating.

No, you don't need to reheat to put a piece of sugar cube in to wedge it open. May take two people - most t'stats I've put in, you can push the center open using your hands/thumb. Resist the urge to use a screw driver or such to 'pry' it open --- too easy to bend that relatively light sheet metal.

So today I looked at some old notes in my original Haynes Manual Volvo 240 --- 1975 thru 1980 Version ---from when I got the 75 - 245. in 1983

anyway --- the Trick I made a note on was:

'old time mechanics kept a bottle of aspirin on the shelf to use when they did a coolant drain/flush....to hold the thermostat open when refilling the system with coolant. No air can be trapped behind the thermostat. The tab will dissolve in the coolant.'

My foggy memory --- Aspirin -- not a sugar cube---but I guess any dissoluble tablet you have around.

If the rad is the original 75 it’s HIGHLY likely that the reason the t’stat was pulled was because the rad is clogged and not capable of cooling the engine properly. I’d look there first.

I owned a 1970 Amazon for quite a while with the same engine and gearbox.

Like any car, when the thermostat opens, the hot water should circulate from the top of the radiator down to the bottom and back to the engine. When the engine has thoroughly warmed up, you should feel heat throughout the radiator, not just the top hose or top of the radiator.

Your symptoms seem to indicate that there is coolant flow through the head and interior heater, but no or very restricted flow through the radiator.

The simplest way to check for that is to drain the coolant and take out the radiator. Then flush it with running water from a garden hose and look for silt like deposits being flushed out. I flush bottom to top first, i.e. holding the radiator upside down, and then again in the normal top to bottom flow direction.

The water from the hose should not meet any back pressure and flow out the bottom as quickly as it enters the top.

If the radiator seems fine, so no blockage and only a little bit of silt flushed out before the water becomes clear, then the next suspect would be the water pump.

Yeah, that is my next task. But I would like to make sure that I don't have any air trapped in the system.

The water pump can be the corporate but I think it was changed within the last 20 years, because it is still shiny. The thing is that before it was fine with the thermostat fully open. The rad was warm, same for the water in the expension thank however the car was always cold except sometimes when I was at a stop light without the heat.

Hello Nanan,

Can you supply a picture of or the part number for the thermostat you installed?

--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Hi,

I ordered this exact one:

https://www.skandix.de/en/spare-parts/cooling-system/thermostat/thermostat-coolant-88-c/1007476/

Part number; 273458

Maybe there is a way to make sure the air is correctly bleed but I don't know which one.

That's the correct style.

Is there any chance you installed the thermostat upside?
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

That's a good assumption :)

I installed the thermostat with the spring pointing down. Meaning that the spring part is in the head.

May be you have no problem except a defective temperature gage or sender.

If you could take temperature reading of the head with a non contact infrared thermometer it could give you a clue of what is going on.

Previous owner may have bored the thermostat to bring down the high temperature reading, but it made the engine run too cold. That is very bad.

I have owned a 1967 B18 but the gage was reading from a copper tube connected to the instrument cluster, no electrical.

That's also possible. However, that does not explain that fact that the upper rad hose is warm while the lower is cold and the water in the expension thank is cold as well.

They often say that if you have a problem, check the last thing you did. I would remove the new thermostat and either reinstall the old one or leave it out. Run it like that for a few miles and see what happens. A clogged up rad is more than possible. With an infra red gun you can check the temperatures across the radiator. If it is much cooler at the lower half or third, that might indicate the problem. Flush or replace as mentioned. Dropping the new thermostat into boiling water may not be the best test. You should bring the water slowly to the boil with the stat submerged and a thermometer monitoring the temps. It may not open properly doing it that way compared to the shock of boiling water immersion. Faulty new thermostats are not unknown.
The B20 engined 240's are very rare so I hope you can keep this one going for a long time to come.

Hello to everyone !

An Update is long long overdue !

So, here's a recap of what I did the last two weeks:

Changed the radiator, expansion tank -> still the same issue

The car says that it's overheating but when I touch the hoses that go to the heater core there are warm but not hot (I can keep my hand around them even though the needle is way past the hot mark).

So I ordered a new coolant temperature sensor -> still overheating

So now I'm stucked... water pump ? Gauge needle ? Thermostat ?

About the fact that the lower rad hose was always cold:
You have to keep in mind that on the B20 the "fan" is always running there is no clutch on this one. I tried to put a piece of cardboard in front of the rad and after 3-4 minutes of idling, the lower hose was warm.

I must confess that after the rad replacement, I was 100% convinced that the coolant temp. sensor was faulty, so I drove the car for 2 weeks (about 120miles / 200 kilometers). So If the car was overheating that bad, I would have blown my headgasket and so far it seems to be fine (we are in the middle of winter in Switzerland BTW).

So now, I don't know, should I order a new water pump and hope for the best ? (mine seems to have been replaced but maybe it's the wrong one and defective).

Try and order another thermostat and see what happen (remember that's what started this saga).

Thanks for your help and don't hesitate to ask more questions if needed.

Regards,
Nanan

I have a 1985 240 DL wagon with a B23 engine and have had similar problems..I have replaced ((everything)) accept the radiator houses and that is my next adventure..So far new radiator, no improve..New water pump, no improve..New temp sensor 2 times, no improve..New thermostats various temps, no improve...Some people say it could be a wiring issue when it gets hot but when the thermo fan clutch kicks in the temps go down fast..Have replaced that thermo clutch fan 2 times, no improve..And currently using the sub tropical one they sell..No improve....If I use my infrared thermometer everything is hot everywhere but well below overheating..Tried a different temp gauge in the dash..No improve..So what i read here was something about radiator hoses and have not changed those yet however they are not old..After the houses i think I'll just shoot myself if that doesn't change things..:)..Pun intended..!!!..I mean what the hell how can this be..Most of the time the temp runs at 3/4 up of the gauge..?????????????...You are not alone!!!..Before all this started it ran about 1/2 up on the gauge..

Hi,

It looks like you have gone around under the hood and hug and kiss things with al the TLC one can muster up!

From your statements you said it has worked fine until recently and the temperature gauge responded to a known for sure change in the temperature of the engine.
Your infrared thermometer says it’s not overheating.
You are not hearing it doing any water boiling gurgling when the engine is off.

Wiring is a possibility if the sensor wire has deteriorated” insulation inside the wiring harness up to the gray connector. Starting in 1984 the engine harnesses had issues!
I think you can get a new harness from DaveBarton.com. His site has a lot!
https://www.prancingmoose.com/volvoharnesses.html#240series
Be careful to pick out your cars year correctly! Check it out!


The main thing that has change is the final location of the gauges needle being higher! 3/4 versa 1/2 way up! Apparently it seems really consistent?
This makes me think that the voltage regulator on the back of the instrument cluster has changed in holding regulation voltage.

On the non cable driven instrument cluster, using an electronic speedometer, this is a solid state device. It is more reliable than the earlier cable driven instrument clusters.
Since your car is a 1985 maybe you have a “hybrid” instrument cluster as in 1984 the cable driven clusters were phased out, but maybe not completely?

Those had “canned” mechanical regulators with heat driven, almost, vibrating points all the way back to my 1978 GT.

In the early seventies, the VW bugs used a light bulb to vary the current to the fuel gauge circuit.
The seasons changing varied the light bulb temperature, of which, change the reading, so very slightly, so you never trusted where empty was for the tank!
Of course, It’s the only reading you want “true’ from a fuel gauge anyway!
The opposite in your case!
If the light bulb burned out your gauge quit, but it was cheap to repair! Ha ha, it’s a VW bug?
Made cheap and questionable, if it would stay that way!
I’m afraid VW still uses that way of designing today! I stare at the new ones with that ? in my mind!

When you changed out the gauge, what type of cluster do you have in the car?

Please remember, I’m working from an armchair and I’m guessing as you are!
The good thing is, I’m not changing the parts!
(:-)
Hope this helps you!

Phil

The 85 has a cable driven speedo..What surprises me is if the thermo clutch kicks in with it roars and the heat dumps fast..It's almost if the antifreeze isn't moving fast enough..The Infrared handheld temp gauge shows heat everywhere sometimes all about the same temp..I have even tried a flow check with the new radiator and water goes through it fast..??..I even put an electric fan behind the aircon condenser to help with flow at lower speeds and that doesn't have much affected..It helps but is is slow..I thought the fan would help with the aircon as well but it really doesn't..I also have 2 different gauge clusters and I put the other one in and temps are the same on both clusters..Again when the thermo fan kicks in the temp goes south fast down to maybe 40% of total gauge sweep...I did try a thermo clutch that was locked on and works great but the gas mileage was only 16 to 18 mpg...Funny other then looking at the gauge the car runs fine and doesn't seem to be running hot..What confuses me the most is why then when the fan kicks in hard it cools so well..Even if I'm on the freeway with great airflow it still looks like it's running warm..3/4 on the gauge most of the time..Inti freeze 50/50 mix and is crystal clear from changing the thermostat so many times..Thermostat is spring in or down in the head..Currently running a 175..Have tried every temp with almost no change..

Hi,

Cable drive cluster so that puts it before 1986. I didn’t know when the change happened.
By you changing around cluster that removes any idea I had about a cluster voltage regulator.
The gauge seems to be working properly and rather reliably I might add!

It appears that there is a wide swing of temperature going on.
The thermostat can only fit in the housing and as I remember, with the spring down.
There is a vent pin built into the thermostat flange that goes pointing up. This is only for venting air since it rises to the top of any hydronic system.

A thermostat could cause these symptoms even if new.
I like a Wahler brand best for accuracy mainly because of the materials they use.
When I test mine, I use vegetable oil instead of water to boil up to the 92C where is first cracks open. It will open further but the flow starts proportionally changes with the slightest increase in temperature.
Oil in the pot is more controllable and even because of its no air quality. You can see when the disc actually moves and how far.
When the coolant is under pressure there is no turbulence like an open pot! It’s a different world in there!
In an engine the water is pressurized and moves more heat that up to a boiling surface temperature to begin with.

An infrared thermometer doesn’t read gases and air!
It has to have a surface holding and emitting heat rays.
I still like using my Scientific Mercury thermometer! It has graduations are in C degrees. Got it a garage sale! (:-)
Easier on my brain when I’m up or below boiling or freezing readings in minute amounts.
Not that others won’t work like a candy thermometers. (:-)

When you are checking areas for heat differential you should be cooler on the bottom hose by up to 30 degrees, if the radiator is fully efficient.
If it wasn’t for the A/c condenser you should see a continuous drop going from the top down and going from side to side evenly.
When you say the radiator flows good but is it flowing everywhere evenly? A water hose test is not one to put all your faith into.
An actual “pumped” flow reading is the final yea or nay!
Radiator shops will test one for you, in hopes you need one.
Each size has its own flow rate.

It seems that the airflow helps somewhat. When using the heater core you add on more cooling capacity. It's the same as having a bigger radiator.
Have you tried turning on and off the heater core?
You want to see if the same thing happens without the fan clutch engaging.
Test under both idle and highway conditions.

The fan clutch operates just as much from infrared heat off the radiator coils than the actual air flowing over it.
The very center of a fan doesn’t move much, if any air, if you think about it! Highway driving only moves air evenly and its the reason for using a fan shroud!
Are you using one? Some people cast them aside!

When you are going at highway speeds you are requiring the engine to do more work.
You are throwing more fuel into a fire, per say, than you do at idle. Yes, it gets hotter and even more so, after you shut down an engine, as the cooling circulation stops completely except by convection!

This is why you hear the newer cars fans running on batteries in a parking lot!
I question the theory or worry of that on a battery.
Again, lights left on in the daytime, on a possible timed out relay failure and an older battery?
What is going on in the lead battery world, is a whole other thread!

Best to Try to rule out the thermostat or the radiator. As to me, it seems to be one or the other.

Hoses are just conveyors unless you can prove that the bottom one is collapsing.
On some large American cars they put springs inside the bottom hose because they have twice the heat problem!
I mean with the internal combustion engine, there is a lot of energy going up in the air in several ways!

Let us know if the testing goes towards a conclusion!

Phil