96 buick park avenue ultra

[temperingloser]

I have been trying to get my car to quit overheating the first time it gets warm. The temp raises up to almost overheating unless I pump the gas a few times then it cools down and stays down. I have noticed the resevoir is always too full when it cools and also the is some some gunk in the radiator. The thermostat was changed just recently and the heater hose elbow but I am not sure why it is doing this. I was planning on doing a flush Monday to try to see if this helps. I tried to bleed this sevral times with no luck. Just wondering if anyone has seen this before and if so I would appreciate any help

[Tech II]

Was this why the thermostat was replaced?

What is the time frame for this to happen? After you rev the engine, you drive the car with no problems?

When it starts to overheat(don't rev engine), feel the inlet and outlet heater core hoses....if inlet is much hotter, back flush the heater core.......make sure you burp system of all air.....

Also, replace the radiator cap.....make sure the hose between the radiator and the reservoir, is clear, and not crudded up, and make sure the rubber isn't collapsing(old)....see if the problem's fixed....

[enslow]

How did you determine that it's overheating? A scantool is most accurate. I believe it can be normal for the temperature to rise to 210°F before the fans come on.

Also, what brand thermostat did you use? I always go with OEM on these, not aftermarkets. Aftermarket ones never seem to open up at the correcy temperatures.

As TechII said, change your cap. It should hold 15 psi. The coolant will not boil as long as your cooling system can hold 15 psi.

[temperingloser]

The reason I replaced the thermostat is because it used to get to operating temperature and then cool down way down and hold there for a while then slowly get back up to temp I assumed the thermostat was staying open too long. Now the initial start up it gets really warm almost to the red and I verified the temp gauge was correct with a scan tool. but after I rev the engine a few times the temp finally comes down. Then it will hold around 195 degrees for the rest of the time. Before I replaced the thermostat I would like to mention that I was still having the problem with the resevoir filling all the way up. I will replace the radiator cap today or tomorrow and see what happens I have thought this could be the problem anyways but havent had much time lately.

[enslow]

Originally Posted by temperingloser

The reason I replaced the thermostat is because it used to get to operating temperature and then cool down way down and hold there for a while then slowly get back up to temp I assumed the thermostat was staying open too long. Now the initial start up it gets really warm almost to the red and I verified the temp gauge was correct with a scan tool. but after I rev the engine a few times the temp finally comes down. Then it will hold around 195 degrees for the rest of the time. Before I replaced the thermostat I would like to mention that I was still having the problem with the resevoir filling all the way up. I will replace the radiator cap today or tomorrow and see what happens I have thought this could be the problem anyways but havent had much time lately.

According to the scantool, what temperature was it getting up to during the initial start?

[temperingloser]

update after replacing the radiator cap it seemed to have fixed the problem I guess it was releasing all of the pressure it needed to open the thermostat thanks for all of your input

[HotZ28]

Originally Posted by temperingloser

update after replacing the radiator cap it seemed to have fixed the problem I guess it was releasing all of the pressure it needed to open the thermostat thanks for all of your input

Glad to here you made some progress. BTW, the thermostat does not require "pressure" to open, it opens gradually as the coolant heats up to beyond 140 deg, then to full open at given max rating.

[enslow]

Originally Posted by HotZ28

Glad to here you made some progress. BTW, the thermostat does not require "pressure" to open, it opens gradually as the coolant heats up to beyond 140 deg, then to full open at given max rating.

I was thinking the same thing too. The difference the pressure cap makes is it allows the system to pressurize to 15 psi effectively increasing the boiling point of the cooling system. The coolant could have been boiling momentarily just before the thermostat opened for the first time. Once the coolant began to circulate the pressure may have built up just enough to prevent further boiling. This is just an hypothesis. However, HotZ28 is right, the thermostat opens just by temperature and not by pressure. Try sticking a thermostat in a pot of boiling water and watch it open as you heat it up. You will see it open at or near the rated temperature.