Temp question 98 grand prix

Thermostats suck. If the new one gets damaged even just a bit there can be enough of a gap to flow coolant when "closed". This small amount of leakage will not allow the car to gain temp. Almost every used car that I have bought in the last 2 years has had a bad thermostat. When I get a new one I flip it upside down and put water on the hot side and check for leaks. I then throw it in a pot of water on the stove and verify the opening temp. Then as cools I check that it has closed completely by doing another leak test. I've had new ones that were sealed untill they opened once then would not close. This test beats f*&$in around with the thermostat neck twice. Not sure where it is on the 3.8 but the 3.4 DOHC sucks.

a 160 degree stat is fine i reckon it hasnt been bled properly or the thermostat is in upside down

If it wasn't bled the air lock would delay the opening of the thermostat and the engine would heat up very quickly (I've cooked a motor). As with installed backwards, it would take awhile for the engine heat to conduct through the thermostat to start to open it and you would run hot. It has to be stuck partially open to run cool.

ok guys, I tried to bleed it and couldn't get any water or air bubbles to come out of the bleeder screw. I had it unscrewed enough because I could see the whole in the bleeder screw. Also my fans didn't kick on until it got to the 3rd mark, then they shut off at the 210 mark. Any answers ?

I have three GM cars right now that do not run hot due to the thermostat passing. Pull it and check it. My '94 never passed 50 C untill you let it idle. Quick check to see if it's your thermostat passing without testing it as described is to use something with two rounded surfaces to pinch the flow on your top rad hose. Your car should heat up alot faster than it has been. Your bleeder is plugged for sure.

do you think that the temp sensor is bad?

no

no, unfortunately I don't have one. What does the temp sensor do?

Just to add clairity. You will have two sending units. One will feed the temp gauge and the other one is the ECT which feeds the above data to the computer. The ECT is also the unit that operates your cooling fans. If you haven't fixed the initial problem of running cool when moving and heating up when stationary and or stop and go traffic you should take care of that first. Your fans will only kick in when you need them and I believe my car is around 210 too. If your gauge was showing 210 and the fan kicked in the sensors are not the issue. If the gauge sending unit fails it will short (show max temp) or go infinite (show 0 temp), same with the ECT if it failed the fans would be on all the time or never turn on. I guess it is possible to fail at a steady state resistance but I've never seen that. The purpose of the thermostat is to keep your engine at operating temp AND to stop the flow of coolant through the rad to let it cool. If it is constantly flowing your engine will run cool under no load and with wind from highway speeds. Under load (stop and go) your engine will start to heat up. Left unchecked it may get hot enough outside to cause your car to overhead as you will not give the fans enough time to cool the fluid in the rad once they kick in. As I said before just because the thermostat was new doesn't mean that it is good.

temp guage wont read anything at all if theres not fluid running over it

You bet it will. I will read the air temp inside the engine. Air is an insulator so it just takes time for the engine/coolant to heat the air and give you a reading. If the coolant level is below the sensor you wouldn't make it very far.

i am having the same problems with my car but the fans get voltage. just enough to give a slight amount of resistance but not enough to turn them. Other times they come on. In what ya'll have commented on. it sounds like i will be taking it to have a doinostics run to see what the computer is reading. I have replaced temp switch, themostat, three fan switches in fuse box. I've insured that the antifreeze is correct, and free of air. I've done everything ya'll have spoke of before i read the comments and I am stumped. some time the fan will come on but most of the time it will not. Computer is all I have left to check out i think. Do you have any other ideas that I can try before I take it to a garage. Thanks.............Sam

I would get a volt meter and test light and go through the wiring before I bought a PCM. I'm not sure what kind of access you have to your relay box under the hood. Easiest method to narrow down on whether its a control issue or wiring issue is to ground out the PCM signal wire at the relay box. With the key on the fan should run with that pin to ground. Try moving the wires/plugs to ensure that it is not a loose connection(s) or broken wire (I have had conductors break cleanly within the wire jacket and make/break the circuit with little movement and with no external signs of the break.) Are you sure that you are exceding the 210 F temp is takes to turn the fan on?

well i got ocean front property in Arizona

just burp it the old fashioned way.

Failsafe thermostats are notorius for "failing". I suggest you try an OEM thermostat that opens at the manufacturer recommended temperature. "NOT" a "Failsafe".

The only thing that has worked for me is putting it up I jack stands. Full the radiator from cap while holding down accelerator. When full hurry and put on cap before releasing accelerator, forcing the pressure I guess. Kinda difficult by self, but I managed