I’ve got a Chevy van that leaks coolant, from a couple of places, intermittently. It does not overheat, and regulates temperature well. Radiator builds up pressure even when it’s not hot (wife drove it a couple hundred yards the other day, and although it was still cold, there was a fair amount of pressure in the rad). None was blowing by the cap into the reservoir, so I replaced the cap. No change. No clog in hose to reservoir.
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So, tonight I drove home from work, it got to normal temp, and I got out to check for pressure. Hoses were hard and hot. The radiator cap was still cold!
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It has good temp regulation, so I don’t think it’s a stuck thermostat. It’s a new one on me. Anyone out there have any other ideas?
Thanks!
perhaps Jester is simplifing the problem too far or you are not explaining sufficently, but it would appear the following saying applies: “If it ain’t broke, don’t fix it.”
I am afraid that it will go from intermittently leaking a little fluid from a couple of places to suddenly blowing out a lot of fluid from all of them at once. (Minor leaks to major catastrophe is not always a long trip.)
Possibly a “blown” head gasket. Check for evidence of oil in the coolant or coolant in the crankcase.
No, oil and coolant are both clean, no evidence of overheating. It just seem unable to RELEASE pressure. And the cap isn’t getting hot. Not a classig blown head gasket symptom, rather the opposite. That’s why I’m a bit puzzled…
replacing the thermostat is quick and easy.
Some testing is called for. I generally start with a cooling system pressure test. Most leaks will be indicated by this, the exceptions being the occasional items that leak when hot but not when cold. The cap’s pressure operation would also be tested by this, but this is moot with your new cap. Finally, I’d test the pressure build-up during the first 30 seconds or so from a cold start.
Next I would test the temperature of key parts of the cooling system from cold start to fully warmed up. This would be done with an infrared “gun” type thermometer. I’d be looking for correct thermostat operation, correct engine temperature (warm), and evidence of proper flow from the water pump and through the radiator.
Cooling system malfunctions can sometimes be quite tricky to diagnose. The more info, the better.
What is the year of the van & the model & how many miles on it?
It’s a '96 Chevy 20 w/ about 130K miles. I wish the theremostat was quick & easy… I’m not even sure I can see it.
Yeah, if it’s a gasoline V-8 with A/C, getting to the stat is a sizable project.
I don’t have any pressure testing eqpt, nor do I have an infrared thermometer. Do I have to give up in disgust and pay someone to do these, or can we think of other options? (I’m used to working on air cooled motorcycles).
You’ve got some intermittent leakage, which you’ve been living with/nursing along.
The radiator cap stays cool. Other than that, do you have any symptom or cause for concern?
If the radiator itself gets hot, engine temp seems normal, heater provides hot air, and there’s no significant loss of coolant, I’m not sure you actually have a problem.
It’s possible that the particular design of your radiator is such that the cap doesn’t generally get hot. It’s possible that the pressure built up in driving a couple hundred yards from a cold start is normal. I don’t think I could make a sound judgment of these things through cyberspace.
To check radiator cap operation, start with a cold engine. Have the radiator filled to the brim and note/mark the level in the overflow jar (should be very roughly about half full). Drive the van for 20 minutes, making sure it gets fully warmed up. Inspect the level in the overflow jar – it should be higher than when it was cold. Shut off the engine, and let it get fully cold again. Normally, the level in the jar would be back where it was before when cold, minus any that might have leaked out, and the radiator will be full to brim. This can be complicated by the leaks, though, in that the system might suck air in through the leaks insteads of sucking coolant from the jar in through the cap.