Cooling system question

[CamWeiss]

Hey guys... wanted to run  something past you to see if it makes sense.


I had drained + filled the cooling system to replace the small lines between the pipe and oil cooler (sandwich style).
I drove the car around and did a quick trip around town - I topped it up as it was just low enough to trigger the low level light.

I later had it idling for ~10 minutes as I tried to sort out another little issue. Went to get back in the car and saw that it was pulling temperature - 230ish deg. I immediately shut the car off as the catch can was starting to overflow on the ground. Waited a minute with both fans running and re-started the car to get it cooled down. However, when I re-started it collapsed the upper coolant hose. Shut it down, removed rad cap, and it came back out to shape. Repeated it again with the rad cap on and then off, and finally started to see coolant flowing again. Topped it off again and continued on.

I *think* what happened was that I had an air bubble in the cooling system. But what confuses me was that it didn't show up immediately instead of driving for an hour plus. Either that, or possibly that the t/stat is starting to fail? I know the cheaper ones fail closed and the good ones fail open - I'm not sure what's in the car.

Either way, the car still isn't keeping temperature down very well - If it's slower speed stuff I need to keep the a/c fan going to maintain temperature otherwise it'll start to creep a bit. Best course of action? Is the best way to bleed the system just to run it with the cap off? I suppose another quick job would be to replace the thermostat and see if it makes a difference.

The cooling system is stock - The rad was replaced a few years ago and the hoses are all in good shape. Could the water pump be starting to fail?

[KevinBuckham]

Last year my newish thermostat failed mostly closed.  Personally, I'd replace that first and see where that takes you.  If you are paranoid, test the new and old one in a pot of water.

[Graeme H Burvill]

Sounds like you need a rad evac, basically puts the system under vacuum and sucks coolant into the voids. Some vehicles are very tricky to get all the air out. I don't personally do this any other way. Any shop should have one and it only takes 5-10 minutes. I would try this before going further.

[Eddie ly]

Burp the system by squeezing the coolant hose a few time with cap on, than open the cap refill and repeat until you don't need to refill any more. Drive the car up to temp, let cool than check and refill if needed.
If your water pump is working .You can also idle the car up to temp with the cap off and watch if your thermostat is working or not. If it fail open you'll see coolant constantly flowing, even when normal operating temp is not reached. If it fail close you won't see any flow at all.

[Jordan Kruger]

Definitely sounds like a thermostat issue.   Take it out and test it in a pot of water if you have a thermometer handy.

[CamWeiss]

Thought about it a little more today. Thermostat is the only thing that makes any real sense here. Even if there were a small airlock in the system the water pump would still bring it through and out - If it's powerful enough to collapse the upper rad hose it's powerful enough to move some air around the system.

Will be replacing it with one of the better thermostats that fails open, should it do so.

[Brett Haviland]

If the system pulls into a vacuum, the rad cap should allow the vacuum to be released, and suck the coolant from the overflow. Try a different rad cap (also check for a blockage/kink in the overflow tank hose, and couldn't hurt to change the thermostat at the same time.

Sounds like a classic airlock trapped inside the engine. Deal with it all the time at work. Best way I get it purged is put the rad cap on, and rev the engine to 5000+rpm for a bit. Usually it burps out pretty quick. U will usually know u have a airlock if ur not geting any heat from the heater.

Best way to avoid tho, is to pull a vacuum on the cooling system and suck the coolant back into the system.(special tool required)

[Ivan Skare]

Run the engine with rad cap off massaging both upper and lower rad hoses. The air should work its way out. Could take up to 1/2 hr of car running with rad cap off. Rev it up and down as well. And ya...ur thermostat could be sticky. Replace its cheap....also pressure test ur rad cap.

[Brett Haviland]

Just replace the rad cap along with thermostat, they are both dirt cheap.