I was and still am having some issues with erratic temperature also. I had coolant leaking along with the milky substance on the bottom of my cap. Took the car in just a few days ago and had the intake gaskets, thermostat and many of the hoses replaced in the system.

Long story short, probably solved the coolant loss problem but I am still seeing erratic temp. changes. The heat is non existent at points and that is when I see the gauge go into the Hot Coolant Temp. zone.

Any more thoughts? Or do you think bleeding it is worth a try?

Mines an '02 Monte with the 3.4 in it.

 

More then likely after all that service you just had done, there is an air pocket that still needs bled out of the cooling system. When the air pocket sits on the temp sensor, it can cause an incorrect reading AND delay the t-stat from opening properly.

BUT, if you are getting huge white clouds of smoke when you first start the car, that could be a sign of a blown head gasket.

Bleed out the air in the system first. Odds are, that will solve your problems.

 

I opened the bleeder valve last night above the t-stat, was able to hear some air get out but was still running into the higher temp. issues. I've had two t-stats in with this problem occurring so I'm ruling that out. I've noticed that the hoses to the heater core and from the radiator are not getting as hot as they normally should.

There was also some increased back flow from the radiator into the overflow reservoir causing it to go much higher than the 'hot temp' line. I did replace the water pump yesterday which did not help.

 

I would get a test done for the head gasket.

 

Just one quick question before I do that. If it was the head gasket would the system run normally during some periods and abnormally during others? Or do you know if the head gasket is an all or nothing type of problem that would cause this?

Thanks

 

The head gasket would allow air to get into the system, so while you were driving the heater would work, and while idling you would raise in temp and lose your heater.

Also, you would feel like you could never fully bleed the air out of the system

 

Thanks for the knowledge. Much appreciated

 

I joined this form to find out an answer to this exact issue. I have an 03 LS (3400). It was throwing a service engine light under heating so I decided to change my thermostat. After that long task was done, I proceeded to bleed my system. I thought I had all air pockets out after 4 or 5 times of bleeding and driving, but the next morning, it did the same thing. Heat turned to cold air, normal engine temp. turned to overheating.

Took it to one of my mechanics, and he bled it 5 or 6 times, burping along the way, and it stayed warm for longer than it had. I dropped off my '85 SS, and jumped back into my '03 to get to work. On the way home from work, 20 miles away, I had to stop 2 or three times. Once I was back home I spent 30 mins. burping and bleeding again and again. Drove it, thought it was takin care of. Drove it a second day, and once again had to stop 4 times on the way to work, and once on the way back.

Took it back to the mechanic and he said he thought it was the head gasket because he did a CO2 test and said it wasn't good. I stopped by my second mechanic, and he said after replacing the intake manifold gaskets and seeing the sludge there from the previous owner, he thinks it'd be best to leave that engine alone, and get a used engine with around 60k on it since it's around the same price. He also mentioned a product called Blue Devil, and mentioned that it was a semi permanent fix. So my questions are:

1. Do you think it is a bad head gasket?
2. Is it worth fixing or getting a used engine?
3. Using Blue Devil on it?
4. If I do fix it, what else should be replaced while doing this.

My list so far is Water Pump, Radiator (Has Leak in it), spark plugs and wires, heavy duty gasket set, and head bolts.

Every time I tried to bleed it, there would just be a lot of air in the top hose, but fluid in the radiator and way above the hot line in the reservoir. After driving it for around 100 miles like this, no antifreeze build up on the oil cap, oil looks good and no white cloud at start up or driving. I have done the trick of jacking up the front end and also putting fluid in it when it was up. I thought it may be the thermostat. I bought a Duralast, but I heard I should have went with an OEM also.

I have been driving my '85 SS for 2 weeks now, and while it is a fun ride, even studs don't help in Ohio's winter messes. Thanks for the help in advanced.

 

Are you sure you didnt put the thermostat in backwords? Also the thermostat could be defective, even though it is new.

 

Quote:

Originally Posted by aussiek2000

Yeah, open one on t-stat hosuing while running

DO NOT BLEED OF THE T STAT HOUSEING WHILE IT RUNNING!!!!!!

THAT JUST PUTS MORE AIR IN THE SYSTEM