1995 grand prix running hot

[lbbudd]

Hello all, I recently replaced the radiator because it was leaking. Since then the car has been running hotter than before. On the initial start up the temp will almost hit 260 then it drops very quickly to about 215. Sitting in traffic it goes up to around 240. This morning I noticed that in park if I rev the eng the temp would drop. It is also saying low coolant but the radiator is full. I know one of the fans does kick on around 240. The thermostat is a pain to get to and haven't had time to look at that yet. I did bleed the lines from 2 spots after I replaced the radiator. Any ideas would be greatly appreciated.

 

[cbrsurfr]

Sounds like thermostat to me since you've already replaced the radiator and bled the system.

 

[monkeydelmagico]

. This morning I noticed that in park if I rev the eng the temp would drop. .

Weak/failing water pump.

 

[boomerang]

Make sure the coolant is topped off in the radiator as a first step. Here's a trick to make sure the cooling system is as full as it can be. It may be easier with two people. With the engine cold, take off the radiator cap. Start the engine and rev it up to about 2500 to 3000 rpm. (The exact rpm is not critical, you just want it much higher than idle.) With the engine held at a steady rpm, fill the radiator until full and put the cap back on before letting it idle.

You'll want to bleed air out of the system at those spots you did prior after making sure the cooling system is as full as it can be.

If you didn't replace the radiator because the car was overheating, then the problem is related to the radiator replacement. Don't overthink the problem. Start with the basics which is to make sure the air is purged from the system and that the cooling system is completely topped off.

Temperature swings like you're experiencing are typically due to low coolant levels.

 

[Zenmervolt]

Weak/failing water pump.

Can also be an air pocket in the system, which seems more likely given the temperature swings and the "low coolant" warning light.

ZV

 

[LTC8K6]

Lower Intake Manifold gaskets?

 

[bruceb]

I tend to agree, you have an air pocket and low coolant. Also change out the radiator pressure cap. I have a 1999 Grand Prix and it runs about 185 Deg normal, up to about 210 in traffic when the fans cut in. But since your temp gauge spiked and then came down, it is either an air pocket or a bad head gasket.