93 GP 3.1 Temp Question

This will be kind of long, so bear with me. Lately, the temp in my
Grand Prix (3.1 MPFI) has been somewhat quirky.

After about the first 10 - 15 minutes of driving, temp will go up
past 220 mark - usually to about 230. It never overheats and this
only happens the first time I drive it each day. After about the
first 10 - 15 minutes the temp will never go that high again, until
I get in the car the next day and the pattern repeats itself.

Under hard acceleration, temp gauge tends to stay stable. However, when coming to a stop (particularly after hard acceleration) temp tends to rise a little quickly, usually up to 215-220 but never really any higher than that. During driving, temp kind of fluctuates between 190 and 205.

So, heres where I'm at - the car is my beater. I really have no
performance complaints, engine has lots of life in it, still has
strong (for a 3.1) acceleration. I'm not losing any coolant - reservoir level has not changed in the two weeks since this issue has come up and I've been paying close attention to the coolant level. But I'm reluctant to put too much money into it.

Any thoughts as to what it might be?

Thanks,
Kevin

It sounds like your thermostat is inneed of replacement. When you first start it, it isn't opening fast enough, and it's not reacting fast enough after hard acceleration, causing the high temps. T-stat are cheap and easy to replace, just remember to bleed the cooling system of air when you're done.

how cold is it where you are at? On my old 95 3100 after a new replacement and bleeding out all the air the new stat on a cold day (20*f or less) it would do that also.

how cold is it where you are at? On my old 95 3100 after a new replacement and bleeding out all the air the new stat on a cold day (20*f or less) it would do that also.

It's been in the high 20s here, but with wind chills, its been in the teens a lot (especially at night).

Now that you mention it, I didn't really notice this problem until the temps turned cold - we were in the 40s and 50s sometimes 60s during most of January which is abnormally warm. But these past couple of weeks have been more seasonal (aka COLD) - highs in the 20s and low 30s (on a good day) with a nasty wind chill on some days. Usually when I do drive it, its either at night or early in the morning, when temps are at their coldest.

Kevin

One other thought to the temp saga...

Could my temp sensors be bad (read somewhere the 3.1 MPFI has two sensors)? I noticed tonight after I drove the car a bit that I parked it and the temp read 190. After shut down and key removal, gauge moved to 210. Turned key to run position without starting the car back up, and the gauge dropped back to 190. This doesn't happen all the time. Has anyone else had this, or have any idea as to what may cause that?

Thanks,
Kevin

Your car does have two temp sensors. One is in the intake near the t-stat housing and controls the computer (AC-Delco part# 213-928). The other is in the rear cylinder head, and has a green wire with an 8" long lead (AC-Delco part# 10232601)

The sensor down by the stat housing is for the computer, while the sensor on the head near the firewall is for your gauge cluster. The gauge sensor gets it's own coolant temperature reading.

Sounds like your thermostat is toast. Actually, I would almost gaurantee it.

In regards to the temp reading fluction while cycling your ignition; Sounds pretty normal.