Okay folks i need your help, the issue started the other day. i was in a long line of traffic. I was probably sitting for about an hour in stop and go traffic, The car started to get hot, i turned the heat on full blast and it was blowing cool. My assumption was that the thermostat was stuck closed. i turned the car off, then turned it back on and the temp gauge when back down to normal operation temp and the heat was burning hot. I changed the thermostat and issue still was occuring, i burped the coolant system, got out all air possible and now the temp gauge still rises but now turning on the heat doesnt do anything and the gauge continue to rise. What in the world could be the issue be??

 

you still have air in the system it sounds like. try using a bleed funnel.

 

Just went through the identical problem with my 99LS and it was a large bubble in the coolant system that took a full gallon of coolant to correct.

 

Oil and filter should have anything to do with the situation but it was done about 1500 miles ago. No leaks of any kind, Cooling fans kick on.

Man i would really hope thats all. I bleed the system for an almost an hour to ensure it was good, then it started doing it again. Should i be bleeding it from the coolant tank or the 17mm bolt on top of the thermostat housing?

I have already used a gallon and it geyser's back out of the resevoir tank, more than ive ever seen a car do when bleeding the coolant system. ill try and burp the system again, just seems like it may be something else yet it has all the symptoms of an air bubble. Maybe the new thermostat is ****

 

Two more possibilities:The engine coolant temperature sensor nipple may not be submerged in coolant and can't give an accurate reading.The fan blade clutch may be in the process of failing and cannot move enough air to cool the engine.Please let us know what the solution is.

 

I will look into those possibilities, the only thing leading me back to being thermostat/air related is that sometimes the heat blows cool, ill shut the car off then it will blow hot again. Its just that this time the temp gauge doesnt go down once it blows hot like it was.

 

Look between the condenser and radiator, my radiator was covered with crap and was restricting the air flow.

 

Could a bad radiator cap cause the issue?

 

if it's old, replace it.

You fill the system from the bolt on the top until it's warmed up, then do the final bleed/burp through the radiator cap on the reservoir. (where the bleed funnel can be used if you have one)

 

So take the bolt off, fill the system will its running until the thermostat opens up? Then put the screw back on, and bleed from the reservoir tank? just wanna make sure i have that right? lol

 

Fill it from the bolt like PD says. When the thermostat opens it'll (obviously) burp the system (using a bleed funnel will ensure that no air gets back in, they call them spill free funnels at some places). Then you reinstall the bolt. Repeat the process on the reservoir tank.

So to answer your question, yes, put the bolt back on then bleed the reservoir. This should go without saying but if you are using a bleed funnel, make sure not to let the fluid empty completely out of the funnel. ALWAYS keep fluid in the funnel, otherwise you're just letting air get back in.

 

Thank you both for all of your assistance. I will post once this has been tried. Im sure this will do it

 

It sure sounds like an air lock and to bleed, you run the engine at 2500-3000 RPM (in park) for a few minutes after it has reached operating temp WITH the heater on Max Heat (you will want to open all the windows).

I have even heard of parking on a slight upslope or jacking up the front of the car to encourage air to run toward the radiator, though I have never had to do this.

Although your engine oil really has nothing to do with the overheating, you might want to replace it as soon as you can. The reason is that overheated oil tends to break down very quickly and lose its lubricating qualities. Just a precaution and cheap insurance.

 

I totally forgot to post after the issue was fixed, I bleed the cooling system from a cold start through the 17mm bolt on top of the thermostat housing and it worked perfect. Car stays nice and cool with no issue's. Thanks again to everybody on CL, great group of people.