Temp Guage: 1999 Pontiac Grand Prix

[jrw1999]

I have a 1999 Pontiac Grand Prix. The needle on the temp guage will float up and down after about five mins. of drive time...after a short period of time, however, it will settle around 200 degrees or so. (The heater will not blow warm air while the needle is floating.) The only time the needle starts to rise is when the vehicle is stopped in traffic, but even then, it never gets into the "red."

The car never overheats and I have yet to see any coolant on the driveway.

Thoughts?

[Tech II]

Well, you have a leak....what you actually have is an air pocket developing....and they are only formed by a coolant leak....the leak may be small enough, so that it is not seen on the ground....

You don't say if you have a 3.1, 3.4, or 3.8 engine,,,,,the first two are famous for lower intake leaks, the third for upper plenum leaks....

Of course, it could also be a basic small leak that just doesn't leak enough, to puddle......could be a radiator, heater core, radiator or heater core lines, water pump weep hole, etc....

Most leaks you can find with a pressure tester installed on the radiator....some are so small, you have to use a coolant dye and black light.....

What you should do, is first thing in the morning, before starting the car, check the level in the reservoir....it should be at or above the cold level mark....then remove the radiator cap.....the radiator should be filled to the top....if it isn't, you know you have a leak....usually you will find crud on the bottom of the cap....this accumulates when air is exposed to Dexcool, due to a leak...