My trusty old 850 with 210,000 on it may be heading into a death spiral. I am getting a pressure build-up in my cooling system and its causing fluid to come out of the overflow. About two months ago, I put a new radiator in and that is when the problem showed up. I replaced the overflow tank lid but its still happening. I assume its the head gasket but I am not seeing any blue steam or antifreeze in the oil. Anyone have any other thoughts?

Thanks!

Lets hope it isn't a head gasket, yet. Because coolant pressure is directly related to heat, is the engine fan working properly? Did you burp the system after replacing the antifreeze - a large air pocket will do wonders?

Is the cap leaking out of the top or around the bottom of the cap? Check the reservior for cracks.

Klaus
--
Proud owner of a 1967 220S

Great suggestion, the fan may not be running. Is there any way to test the fan or force it on? I just went out with a warm engine and let it idle for 5 minutes, usually I have the fan on but I don't hear it. I hit the little fuses with dielectric grease up in front of the fan. I wonder if the motors gone. Wouldn't that throw a code? I currently have no codes. I wonder if I screwed something up when I put the new radiator in. I just checked the plug that sets on top of the fan and four little fuse deals on the top of the radiator trim piece. Are there any other connections? Man this could be some good news.

Thanks!

Those little "fuses" are relays. One is for the fan, you will see the wires going to the fan motor.

You could try jumping the wires, but that could mess up the relay. It is best to check to see if any of have voltage. One of the wires goes back to the ECU, very low voltage, so jumping that one with 12V would be a disaster.

I suspect that something is unplugged. Be careful, the fan could nick your fingers!

Another thing to try: turn the AC on. The engine fan is also supposed to turn on then.

Klaus
--
Proud owner of a 1967 220S

Thanks again Klaus. One other question, where is the thermostat on this car? I am getting normal engine temps, I wonder if the thermostat is gone, but I don't see anywhere that one would be located.

Thanks

Two items. The thermostat is located behind the power steering pump, next to the intake manifold where the top radiator hose enters the engine. Two torx screws hold it down. If the OEM thermostat fails, it normally does so by failing to close. An open thermostat will keep the engine temp cold for a very long time after start up, most notible in the winter when you want cabin heat.

There is also the engine coolant temperature sensor, just below the thermostat, with a 2 wire plug. If the ECT sensor fails, there is usually a code stored. The ECT sensor tells the ECU when to turn on the engine fan.

If your 850 is a 1994-5, the DTCs are scanned from the engine bay. 1996+ cars need a scanner, but some scanners are better than others. Usually, those that can read Ford engines work well with Volvo, but only do engine related scans.

Go to an autoparts store and borrow a scanner, the check engine light does not need to be on for codes to be stored. A very good Volvo indie will have a Volvo scan tool, which can check the fan operation, just like DIY for 94-5 cars.

Klaus
--
Proud owner of a 1967 220S

Thanks again Klaus. Unfortunately I have a 93 so it is the old scanning Jetronic scan system. I don't think a scan tool worked on this car. The interal system is giving a 417 code which is passengers side interior temperature intlet fan seized. It doesn't appear related.

Other than with the AC on, the fan is not coming on despite the coolant seeming hot and coming out from under the overflow cap, but it has been in the 30's and 40's here so I am not sure the fan should be coming on. The ECT sensor sounds like it could be the issue, but I guess the only thing I can do is take it to a shop if it isn't throwing a code.

B-1, 4-1-7 is an easy fix. Just pop off the cover behind the passenger side grab handle and vacuum out the dust bunnies.

Because the engine fan comes on when you turn on the AC, the electrics are probably hooked up correctly. You can check the resistance by unplugging the ECT sensor and probing the sensor with a multimeter. You should get the following resistance when the coolant temp is at:
32F = 7200 ohms
68F = 2800 ohms
104F = 1200 ohms
212F = 150 ohms

The code in A-2 for a non-working ECT sensor is 1-2-3.

Also wonder about the overflow bottle itself. Inspect the top carefully if it is leaking below the cap, it might not be sealing completely.

Klaus
--
Proud owner of a 1967 220S

I am throwing no codes on the A2 check. I am pretty sure its not the bottle. The next morning after the engine is cold there is still pressure in the bottle. When I open it, it sounds like a bottle of soda, which it never used to do. If there was a leak in the bottle, I think the pressure would be gone before morning. Also, the bottle itself is starting to bulge some form the pressure. I have been watching the temp gauge, it heats up pretty fast and I have heat after about a quarter mile in the morning so I don't think the thermostat is stuck open. I guess it could be stuck shut. The engine coolant temp sensor would make sense as the culprit.

Thanks

This is not making any sense. When you replaced the cap, was it the same color? Green? They are color coded for the amount of pressure allowed. If the pressure gets too high, the cap is supposed to release it.

If the thermostat is closed, the radiator would never get hot and the bottle would also not get hot, and your engine would be cooked by now.

A new cap is cheap, try one.

Klaus
--
Proud owner of a 1967 220S

I agree it makes no sense. I bought a new overflow cap and it still leaked so I bought a second new cap to be sure and this one was blue/green like the original one that I had on there. The newest one also leaks. The strange part is that I still have pressure in the system the next morning after not driving. The fluid isn't hot but there is pressure.

Before you mentioned burping the system. I took the cap off and squezed all the hoses to get the air off. Is that enough? I have leaked over 3 gallons of fluid out of the cap so by now I would think any air bubble would be gone.

Early tonight I ran the engine and I am pretty sure that I can hear the thermostat working, of course it may not open all the way. I may take it out this weekend and do a boil test. I still don't see how the pressure would remain after the engine cools if the thermostat was the problem.

I just went out and ran the engine with the AC, and the fan did come on. Last night when I regreased all the relays, I might have corrected a loose connection but it didn't feel like anything was loose. Fluid is definately coming from under the lid of the expansion tank and I am certain it isn't the bottle, in fact the bottle is looking a little bloated from the pressure. Its strange that after putting in the new radiator that now I have all this extra pressure.

Thanks