Engine Temp Problems

Hello all,

Have a problem with the old 01 Venture...

Heat inside was not getting very hot for a good while. It took a while to heat up and even there it wasn't as hot as it should be. More recently it started to overheat very frquently.

We replaced the thermostat (fun job... ) now the overheating isn't as frequent but it still overheats. Also a new problem, the temp will fluctuate from 1/4 to 3/4 within minutes at which time the inside heat also goes from cold to hot in the same order and eventually it overheats. We always stop it before the red!!!

It appears that there is enough fluid, the overflow is full and when you open the Rad cap, coolant comes out. We bled the system several times however it does appear to be taking on air unless there is a large amout stuck somewhere and we are not bleeding it enough. We have also not used the DEX COOL fluid but I don't think that would have caused the issue...

Anyone had this before or would have some suggestions?

Thanks,

Robby

If you have rear heat, is it hot? Hows the radiator hose feel?

I had a similar problem with mine. I replaced the temperature sensor and it fixed it. The temp sensor was not turning on the electric fans, even though the temperature gauge was working fine. If you turn on the ac, the fan will come on and the engine temp will get lower. I know this is not a good solution for the winter.

No there is no rear heating in this van and which hose should I check, the send or return? Am I looking if it's hot or not?

Thanks for replying...

Just checked, both rad hoses are hot, cooling fans don't come on when AC is turned on for a few minutes...

Is the temp sensor you are speaking of the same that controls the temp guage?

OK well we got confused with the info concerning the heat guauge and air temp... when she accellerates the heat gauge goes down and the air temp thrown is warm, when she stops at a red light for example the heat gauge goes up and the air inside gets cold....

now that I have this info is it possible that the water pump is starting to fail? or could it be the system needs to be flushed?

sorry for the confusion : )

I would defintiely have the pump checked and get the system flushed. Might try belching the system again, the sensor by the water neck is the fan switch/ dash sender. The PCM's sensor is in the head and my fans dont kick on untill like 235* for the PCM. My Uncle (now unemployed GM mechanic - no more GM for me) said that was normal (we scanned it with a TECH2 after replacing the thermostat due to not heating up.)

Hate to say it but from the symptons you describe it sounds like a blown head gasket.

Man, we had the head gasket replaced approx 3 years ago... is there anything else I should check for signs of it failing??? I really hope it's not that : (

I am pretty sure that your electric radiator fans should come on as soon as the ac is turned on. You might want to check out your fuses or relays (whichever is for the fans).

I don't know where you are located but if it's too cold for the a/c compressor to operate I'm not sure if the electric fan will come on even with the a/c button on.....

Pull the cap on the radiator with engine running, look for bubbles in the coolant (leaking head gasket).

That sure sounds like you have an air bubble in there. I don't know if it was left in there from the thermostat change, or is being "injected" by something else (hope not head gaskets). But I would definitely try to bleed any air out of the system and make sure the hose between overflow tank and the radiator cap is not clogged. While you are at it, if you did NOT replace the radiator cap recently (in the last year or so), I would do that too.

To bleed the system, use the two bleed screws - there is one over the water pump (on the right side of the engine) and one near the thermostat housing. You can see some pictures of the locations here (http://www.my-chevy-venture.com/chevy-venture-bleed-valves.html).

Good Luck!

Its the head gaskets man. Sorry, but those are the general symptoms, especially the bit about overheating when at idle but cooling under acceleration. Only a head gasket does like that I'm sorry to say.
Search these forums. They are full of folks with the same problem exactly as you describe. Its the head gasket.

Head Gasket...SUCKS..but my van did the SAME thing...didn't really show any other symptoms....Van temperature sensor was replaced, followed by the intake gaskets...van still did the overheat dance...temp gauge going up then down...showing overheat, pull over it be gone...from what I understand air is getting into the system and steam blows by the sensor making it think it is overheating...UNFORTUNATELY FOR ME...I DIDN'T HEED the info on this board and did the intake gaskets....had to turn RIGHT AROUND and have the heads done and WASTED the money on the intake gasket repair...my mechanic was stumped as the symptoms for a blown head gasket he was looking for weren't what my van was displaying...but for the Venture..

No heat in cabin
Erratic temp gauge even when the system is full
Overheating light

Sorry your mechanic didn't pick up on those symptoms but they are typical for head gaskets. I use to drive school buses ans we had a fleet of Chevy mini buses with I believe they are 5.9 diesels and they all showed the same symptoms as they blew head gaskets one by one. Whenever we saw the temp. guage doing the dance we knew it was time for a head gasket job.