Overheating Problems

[Cueman]

OK, here is the scoop. '95 Cutlass Supreme 3100. About two weeks ago I decided to go ahead and change the coolant, thermostat, and the coolant temp sensor, because my engine was running a little hot.

 

Ever since I did all of that the tempature has been all over the place. Hot then cool, hot then cool. If I let the car idle for 15-20min it goes all the way up to almost the HOT mark, once I rev the engine it almost immediatly goes down to about 1/4. The same thing happens when driving in city traffic. Once I get to a stoplight, up to hot it goes.

Also when the temp goes up to hot the heat turns cold.

 

I have tried to bleed(using the thermo housing screw) every couple of days. but it dosen't seem to help!

Could this be the waterpump?

 

Any help/suggestions ?

 

Brian

[NeonKnight]

how did you bleed it? did you bleed the system while the engine was running?

 

possible water pump but i dunno. wait for the gurus to get to this

[DiscoStudd]

Sounds to me like you got a bum thermostat. See if you can exchange it for a new one and try again.

 

When you're filling up the radiator, alternate between squeezing the upper and lower radiator hoses with the rad cap off. Top off each time the level drops. When you get to a point where you can't "burp" any more air out, start the engine with the cap off and add coolant as necessary. Run the engine for a couple of minutes, then top off the rad and put the cap back on. Fill the overflow tank to the "HOT" mark to compensate for any tiny air pockets that might remain. Once you drive around a bit, the level should stabilize and you're good to go...

[Cueman]

Thanks for the help Disco! I will try and put a new thermo in this weekend.

I also have another question. I have also noticed that my fans do not seem to come on when the engine is hot.

 

 

I did check the operation of them when I changed the CTS, and when I unplug the CTS, they both inedeed come on.

 

Would this be one of the problems, because I don't believe that they are turning on.

 

What else controls them?

[Crazy K]

I'm having the same problem in my 95 CS.

I am in the middle of changing the thermostat, to be followed by another flush. My coolant is nasty because I used stopleak due to a bad heater core. The temp problem got worse after I replaced the heater core. I have a new water pump to put on next, but I suspect that the combination off dirty coolant and possible air pockets in the system. I know that I lost alot more coolant from the system than I've been able to put in.

 

I had one unusual problem - I had to pull the guages and clean the contacts for the temp guage. I suspected a problem there because the needle would peg, but the overheat light would not turn on. I grounded the sensor wire and observed the guage peg but the light worked. I cleaned and greased the contacts, removing corrision that existed because this car was flooded or rained though due to all the windows being knocked out by vandals Now the needle is consistent, but stays at 'maximum-normal' range mark.

 

I replaced both temp sensors and observed that the car still did not turn the fans on. I believe this is actually normal for wintertime with the ac off. If your ac works and you turn it on, they may come on.

 

 

may I recommend.... remove the temp sensor by the thermostat, pop off the belt, and spin the water pump by hand to gurgle out any air bubles that will likely be trapped there. Unfortunatly I thing the design of the 3100's sideways thermostat is a real flaw in our cars.

[Cueman]

OK, A little update...I get into my car after work today, after driving not even 10 minutes the temp gauge goes all the way into the red zone, and the heat turns cold.

I pulled over and popped the hood. The primary fan was on so that works

But the coolant resivoir was almost full! Probably about 4 inches above the hot mark. I squeezed the upper rad hose and it stayed compressed, like there was a vacuum on it. i opened the bleeder screw, and reved the engine until coolant came out. After about 2 minutes the temp came down, and the fluid in the overflow was back to normal.

 

Would this be symptoms of a bad thermostat? Or could there possibly be more air in there?

 

HELP!

[THe_DeTAiL3R]

If it went back down to normal (hot mark) when the engine was still running then hopefully you got the damn air out. Yeah, I also know it's a pain in the ass (especially after taking the engine apart).

 

 

At this time of year it takes a while for my car to get hot enough for the fan to kick in. Like running on the spot with the hood closed, maybe 20min until it gets hot. A 10min drive woun't make it hot enough for the fan to kick in, but the heat would be working properly...

[Crazy K]

if you loose your heat that means that you are probably sucking air thropugh the heater core, btw. don't forget the bleeder valve for the coolant bypass, by the waterpump.

[Cueman]

I have probably blead it three or four times like that. cracking open the thermo bleeder screw and reving the engine until it squirts out, then closing it. There still seems to be air in it everytime.

 

Would the thermostat not opening3 cause the overflow to fill up like that?

[THe_DeTAiL3R]

yes