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My wife's been driving my C70 all week - since the head gasket is failing in her 940 and the dang thing is on backorder... Loss is intermittent and minimal, but it's still a concern.
Anyway, she pulled up to the house in the c70 and the expansion tank cap suddenly started spewing hot coolant under the hood. No warning, no overheat, nothing ruptured. The OEM volvo expansion tank was quite "swollen" when I investigated, but all the hoses are intact - most are new Volvo OEM and Samco silicone. The entire cooling system is new - thanks to a failed head gasket in August. The only things that I didn't replace were the hardlines to the turbo and water pump itself.
Can't quite describe how much angst this new problem fills me with... Bit too much happening all at once...
Wife said there was no unusual road traffic nor was she stuck sitting in traffic for any length of time. It's pretty weird.
So, I let the car cool and noted that a fair amount of coolant was gone. Topped it off, and ran the car for a quite a while - seeing nothing. Had to top the coolant off again (not usual with a hot engine and lost coolant).
Ran two cycles of letting the car cool, checking the coolant level and then running the car at high revs for a while. I *carefully* watched the expansion tank for coolant loss or worse-bubbles and over-pressure in the coolant.
Saw nothing. I know that expansion tanks don't blow-off for no reason.
I've already replaced a head gasket on this car. I'm seeing none of those nightmarish symptoms so I'm hoping that I simply had a stuck thermostat...
Any chance that I'd be that lucky?
We're trading back tomorrow. my short commute is a good test for car with possible problems... short drive, close to home, etc...
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OEM thermostats usually fail in the open position, cheap ones fail in the closed position and can be disasterous - no hot antifreeze flows to the radiator or coolant bottle.
Did you ever swap out the ECT sensor? If the engine gauge read 'normal' and the system blew, that is where I would look first. Also, the engine fan should have been on high speed. Check the resistance on the ECT, and if bad, replace it ASAP.
If the temp gauge goes up, make sure the fan relay is working properly.
Klaus
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There is no present time, just the past and future
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Drove the car again today, nothing funky, but I'm feeling incredibly paranoid.
The ECT sensor... that's the one screwed into the thermostat housing? That's still the original unit. Maybe time for a new one. Especially considering all the problems the car had last fall with the head gasket failing and coolant spewing everywhere...
Fan seems to be running fine. Is there proper testing procedure somewhere? Ohms etc?
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http://www.brickboard.com/AWD/volvo/1519900/850/heating.html
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There is no present time, just the past and future
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Klaus, thanks for the link.
What's your opinion on Dexcool? It rates favorably in the FAQ, so that's all this car has been running. However, someone on TB suggests that it's a problem for Volvo Engines...
It's the only coolant this car has run since I rebuilt/replaced the cooling system. 'course this is a complete whiteblock, no at Bimetal, like the B230FD...
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The FAQ are for red block engines, I wouldn't use it for the 6 cyl 960 either. I suggest using Zerex G-05 or OEM($). Note: the G-05 and Dexcool are not compatable. Use only distilled water for your mix.
If you do not drain a quart or 2 before swapping out the ECT, cover the alternator with a shop cloth - it does not like to be coated in antifreeze.
Klaus
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There is no present time, just the past and future
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+1
Zerex G-05 is the one to use if you can't get OEM.
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1998 V70 AWD->FWD->AWD Turbo 220k+
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Dexcool causes the the typical "eats the solder in the radiator" problem? or is there some other issue with the whiteblock engines themselves?
I always use distilled to dilute and never mix colors.
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I never worry about the radiator, it is the block that becomes porous.
Klaus
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There is no present time, just the past and future
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Guys over at TB are thinking my HG is failing again... :( I'm not seeing the symptoms that I saw last time, but the specter of another HG is none too pleasant.
If that repair is in my future (again), I'll probably get a junkyard head from an 98 S70 and get it machined if there is any sign of overheat.
The swollen/pressurized expansion tank seems to be a key symptom. Bad cap or much worse - exhaust gasses in the tank... hasn't happened since Thursday - even with highway and city driving.
I'm planning to test the ECT today (Yesterday turned into a Yard Work day) will post what I find out.
Tentative plan is to replace the water pump and get a new OEM expansion tank cap. Then thoroughly flush out the Dexcool and put in OEM or Xerex coolant. Will probably put in OEM, unless the price is truly ridiculous
TB folks also stated that Dex usually damages the heater core - which I already replaced with a cheap FCP unit just a couple months back.
Will also note that there has been no coolant loss or blow-off since Thursday, and I am checking it religiously.
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I seriously doubt your head 'warped' and your new HG failed. Unlike the red block engines, the block and head are the same material and warping is a non issue.
If exhaust gases are getting into your antifreeze, there should be a million bubbles in your overflow tank.
You still need to check the ECT and the fan relay.
Klaus
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There is no present time, just the past and future
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Tested the ECT with a digital multimeter.
Learned *very* fast that you shouldn't start or run the engine with the ECT unplugged... immediate CEL, constant fan, and hard start... I ended up reading the resistance on the plug after shutting down the engine. Cooling fan wouldn't shut off until I cleared the codes... Oh well. got another month until safety/emissions inspection...
Results
(Read on the 0-20 ohm scale of my digital multimeter)
4.96 -- Cold engine
0.69 -- 1/8
0.43 -- 1/3
0.28 -- 1/2 (Normal 3:00)
0.16 -- 1/2 (when cooling fan came on)
0.19 -- 1/2 (after extended high rpm run)
Seems like a nice curve, but the numbers are somewhat different from your test procedure...
Cooling fan definitely works, but unsure if there's something else I should be looking for...?
Also no bubbles in the expansion tank, no radical expansion of fluid in the tank, no vanishing of coolant since the last check.
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Those numbers look to be a bit high, I multiplied by 1600 to get into the 30K scale normally used.
The engine fan shouldn't come on until the engine temp gets to around 220F or so. I guess your fan relay is OK and can be ruled out.
Klaus
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There is no present time, just the past and future
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Do you think "high" indicates imminent failure of the unit?
Unfortunately, I don't have a thermometer to compare temp to resistance
It's not terrifically expensive, but there's little point in replacing parts that are working fine.
I'm leaning towards the expense of a new oem cap from Tasca...
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Save yourself shippin and go to your local dealer for a new cap.
High is not imminemt failure, probably just not knowing the correct temps. High results in leaner burning engine.
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There is no present time, just the past and future
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If it were just a cap, I would. $10 min shipping charge is not worth it for one or two items - but I'll probably be ordering several things.
Am planning to go with my local dealer for the coolant. Gotta do the water pump, might as well do as much of it as possible while I've got the system open.
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FYI - When I replaced my radiator last year I bought OEM coolant from my local dealer. It was about $30 for the gallon - ouch! IMO - it was worth the cost. Peace of mind for me and cheap insurance for my cooling system.
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