Car temp runs around 210 then drops down

yeah for the last week, i notice that randomly my car will heat up to around 210 on the temp gauge then drop back down to the first notch and be normal. I have tried to find out what causes this, i thought maybe it happened when i floored it. But it doesn't do it all the time when im at WOT. I have no idea whats going on and why my car is getting so hot then dropping down to normal again 20 seconds later. I just had a coolant flush and fill today to.

that seems pretty normal for the thermostat to cycle or when your fans kick on. Remember thes guages aren't very accurate. When I run my autotap I can see how much my gauge is off.

Wait till you change your T-stat and see if that makes a difference..~Larry~

My 3100 does the same let off the gas coast to a stop temp creaps up to 210 (fans dont turn on untill 228 stupid GM) step on the gas temp goes down to 198-202 watched it on snapy's scanner. Put a new t-stat in (195 F) pretty sure I got all the air out. I am kinda thinking of the lower intake gaskets are bad but is does not seem to use coolant. :dogpile:

My 3.1L did the same exact thing. I did notice that I had some rusty sludge in my radiator. However i did nothing about it and eventually, it overheated and after that happened the rusty sludge in the radiator got worse, I started to slowly lose coolant(with no signs of leakage), then I found a small leak on one of the lower intake manifold bolts right next to the thermostat. I still procrastinated and soon I found small leaks around most of the lower intake manifold bolts. Now I have to fill the radiator up every day and because the orange coolant costs $8 a gallon I've been using water. Needless to say, this week my water pump started trickling water from it AS I'm pouring in the water! However that stopped and I think it's because the sludge might have clogged up the hole. I bought a new pump and thermostat and I'm going to flush the system before I do anything. And, I MUST change the lower intake gasket ASAP or else I'll get a nice repeat of my problems.

It's good that you had your system flushed and hopefully the thermostat was changed. I think my problems started with the sludge in the coolant system. I think it built up on my thermostat causing it to stick (thus the erratic temp readings) and eventually stuck to the point the engine overheated. And I believe the overheat caused the already weak lower intake manifold gasket to fail(or at least partially fail). The water pump failure is most likely from me using water since it doesn't have the lubrication properties that the orange Dex-Cool coolant has. The only thing I can say is expect the lower intake manifold gaskets to start leaking since this is a common problem with our Grand Prix's. Hopefully it won't happen soon if at all.

Dan

The only thing I can say is expect the lower intake manifold gaskets to start leaking since this is a common problem with our Grand Prix's. Hopefully it won't happen soon if at all.

The 3.8 SC motors dont have that problem.


~Larry~