1995 3100 overheating

[andrewgrant]

i have a 95 grand prix with a 3100 with an overheating issue.the problem will only occur after the engine has completely cooled(overnight and such).the temp will continue to rise as if the thermostat never opened and i have to stop and let it cool down.after about 4 or 5 times of cooling down, it works normal and stays cool until the next time it completely cools.the thermostat has recently been replaced, the heads are not warped, the head and intake gaskets are new, along with the water pump.i thought it was losing its prime, but when i take the bleed screw out, only antifreeze comes out-no air bubbles at all.

[IsaacHayes]

Did it ever have dexcool in it? It might have a clog somewhere. Drain the coolant out (save it if it's new) and do a radiator flush. Don't forget to put the coolant back in when done (it's cold out!)

[andrewgrant]

im sure at some point in its life it had dexcool, but when i got the car it had green, and i certainly wasnt changing it back over.it was flushed probably about 1000 miles ago.it did it before that and doing it didnt change anything.

[IsaacHayes]

And you are sure the thermostat is good? It could be dexcool residue clogging the radiator or heatercore...

[andrewgrant]

it started cooling normally for a couple of days, then i drove it down to toledo(about 300 miles one way from my house)and back with no problems, then today it started acting up again, and now the gauge wont go down at all-before it would after letting it sit for a couple of minutes at a timethe thermostat in it is new, and its the second one ive put in it within about 5000 miles, so regardless of symptoms, i dont think its that.But i could be wrong.

[crazyhorse]

Does it ever lose coolant?
This sounds SOOOO much like an air bubble in the coolant.

Have you changed the radiator cap? Remember, water boils at higher temps under pressure. A bad cap won't hold pressure, and will actually cause air pockets.

Please don't take this wrong, but are you installing the thermostat in the right direction? I don't mean anything bad by this, just covering the basics

[andrewgrant]

i changed the radiator cap at the advice of my father about a week ago, because the coolant was getting pushed into the overflow bottle but not being sucked out, thus leaving some of the radiator empty. the new cap did not help it.And no offense taken, crazyhorse, the thermostats are in the right way, but there was no way for you to know, and had they been in wrong, that would have helped. i tested the thermostat that was in it today, and it was stuck, so i bought a new one and (after testing it) put it in.I havent completely bled the system yet though, as the temp. outside is below zero and i dont feel like going out there.

[crazyhorse]

Pushing coolant into the tank, but not pulling it back out is a sure sign of a leak somewhere. Just as the cap hols pressure, it also holds vacuum. If air can get in somewhere besides the overflow, it will. I'd guess you have a pinhole somewhere. Unfortunately, the only place it can leak without going on the ground is the heater core, or internal to the engine.
Since you seem to be suffering from a tick too I'd double check your oil. I'll say a prayer that you don't find a milkshake, indicating a blown head gasket.

[andrewgrant]

Head gaskets and intake gaskets are brand new, oil is fine; I'll check the heater core.

[nixtux]

I had a similar issue with my 95' Cutlass.

The problem was /w the fans. Only one fan would click on. Solution, electric grease on the Hi/low-Fan fuse under the hood.

Before I figure out the fan issue I just turned on my heat and it cooled off. I also found that clicking the A/C on/off a couple times would get the hi-fan running and it'd also cool.

Maybe these are not relevant but those were my "getting" hot issue. It only once clicked the "HOT" light which was in the winter when I got stuck. Shortly after I bought it; after that i monitored the heat gauge like a hawk.

[IanSzgatti]

have you changed your temp sender(s)