Temperature in 2002 Grand Prix Rises to 230 F on Cruise

[Brandybuck]

I just replaced both intake gaskets on my '02 Grand Prix GT (3.8L, non-supercharged, 114,000 miles). In the process I also replaced both the thermostat and the temperature switch - not that they were bad, but I had easy access to them and wanted to take advantage of it.

Now, however, running on cruise control at 55 mph when 60 degrees Fahrenheit outside, the Grand Prix will level off at about 220-230 degrees Fahrenheit. Though I can't give you a "before" temperature because I just bought the car, I don't like this for four reasons:

1) I drove a 2000 Grand Prix GT (also non-supercharged) for two years before I bought this one. The temperature gauge on the '00 model almost never exceeded 185 degrees Fahrenheit.

2) Revving the engine to 3500 RPM for 10-15 seconds raises the temperature to the beginning of the red mark. The cooling fans kick on and bring it back down a bit, but I don't like the idea of the temperature getting anywhere close to where they could damage the engine.

3) A small amount of smoke comes from the oil dipstick after the car is revved to 3500 RPM as described. There is also a burning smell. (Or could this be from coolant getting in the oil as per the recent intake gasket change?)

4) The upper radiator hose is too hot to continuously touch at 230 degrees - is this normal?

I would appreciate all suggestions and advice.

[Tech II]

That's too high.....Going down the highway with air across that radiator, should be 190-195, and cycling.....

Was it overheating before? Sure you haven't removed all the air from the system? Let it completely cool down.....then check level in reservoir AND radiator.....Those funnels with the adapters that attach to the radiator neck, are great for venting these engines....

[Brandybuck]

Thanks for the tip regarding the funnel adapters, Tech II

I followed the GM Pontiac manual procedure for refilling the cooling system, complete with opening the bleeder valve on the thermostat housing. I just checked after driving the car a mile, and the coolant level is full at the pressure cap. The overflow tank is also at a good level. Does this mean all the air is out of the system?

It WAS overheating somewhat before as well - I'm not clear on how much since I hardly drove it before I changed the intake gaskets. Aren't the fans supposed to turn on before 200 F?

By the way, what do you mean by "cycling?"

[rickisrad]

I think that he is referring to the fan off/on cycle. Some times these are hard to bleed after an intake change. as the car is running crack open the bleeder and let the coolant flow out at a good pace making sure to constantly have the coolant full at the radiator. watch for a constant flow without any air spitting. sometimes it can take a second time after driving.
A few questions and comments......
Have you done an intake before? does the car idle normal? Did you use plastic gaskets? Did you re-use the plastic plenum? sometimes when one of these plastic parts are overtightened they will crack and cause several issues. It is also important to tighten in sequence and torque all of the bolts. Not saying you did this but, maybe an improperly installed thermostat?

[Brandybuck]

Thanks, rickisrad.

Never done an intake before. I believe I've installed this one correctly, however, since I'm not experiencing any coolant or oil loss, or observing any leaking.

The vehicle idles normally.

Used plastic gaskets from Autozone.

I reused the plastic plenum. I didn't observe any damage, including melting around the EGR tube. It appeared to be in good shape, so I reused it.

I was also careful to follow the torque sequence and specifications of GM for my Grand Prix GT.

I'd been warned about installing the thermostat correctly; I made sure to do so.

I really appreciate your response and detailed questions, rickisrad.

I've actually resolved the issue elsewhere. #1, I remembered that this car had been overheating before I changed the gaskets. #2, I found out that it actually isn't overheating at all. A mechanic measured the temperature of the thermostat housing itself with a digital point 'n read thermometer, and another mechanic read a normal temperature of 201 F from the PCM while the gauge read 230 F.

So I'll need to replace the gauge cluster. Any ideas for a cheap replacement cluster?

[rickisrad]

you should be able to find one at Morads or on Ebay. look for any breaks in the wire or bad contact points for the temp sensor. just to be sure. Or you can buy an aeroforce scan gauge that way you can monitor it and everything else that way.

[Brandybuck]

Good point regarding the possible bad wire. I'll definitely check for that.

I've virtually decided not to replace the gauge cluster, because I'll be tampering with the odometer. If I do that I'll have to write down the original reading somewhere on the frame, and I'm sure it will decrease the value of the car somewhat as well. I'll also have to remember that the odometer reading on the new cluster is incorrect. (Let me know if I'm incorrect in any of these things.)

Unless I'm wrong about the odometer issue, I'll probably get an add-on gauge just for the temperature and mount it somewhere in the car. On that note, what is the aeroforce scan gauge rickisrad mentioned? Is it better than a simple coolant temp. gauge?

[DeltaP]

How is the cooling system in general? Is it clean inside? Did it have antifreeze in it, what color, is it mucked up, did you flush completely? Do you have good flow through the radiator core? What coolant are you using, Dexcool? Heater fully open during the refill/bleeding process? Do you still have the old temperature switch? Just some thoughts.

[rickisrad]

the aeroforce interceptor is a digital scan gauge and it scans everything on your car. you can read and erase codes with it and it is programmable for various different functions. Also a great addition if you plan on any performance modifications in the future.

here is a link to more information. http://intense-racing.com/Merchant2/...00_Electronics

[Brandybuck]

DeltaP,

I've actually isolated the issue. The car never was overheating at all - my gauge is wrong. I know this because the PCM reads a normal temperature when the gauge reports a very high temperature. Thanks for the help, though.

[DeltaP]

Look into Dorman Products for aftermarket instrument clusters. HTH