Thread: Weird engine temp problem

Hi all,

So, I've had my 1998 GP GT for 3 weeks now. It has about 143k miles on it. The issue I am having is the temp will spike high, near the red zone but, the temp warning light never comes on, on every three or four drives if it doesn't sit for a few hours. It doesn't matter the time of day, I've had it happen in the morning at 60, mid-day at 95+ or evening in the low 80's, also the style of driving doesn't seem to effect it, it has happened in stop and go as well as on the highway. This past weekend I replaced the tstat with 195 tstat and the radiator cap, bled the system and filled up the coolant, there are no visible leaks. From Sunday through Wednesday the issue seemed to be solved and has been running 10 to 15 degrees cooler.

So, on my way to work this morning the car never went about 195. Went home on my lunch break to pick up something for work, the temp went to 205. I was at home for 1/2 hour and left to go back to work. About ten minutes into my 15 minute trip to work, the gauge climbs to just outside of the redzone. I turn on the heat and the temp falls back into the 210 range in a couple of minutes. When I get to work I pop the hood and I see both fans running (Air off), while the gauge reads 195-200 range.

This one has me scratching my head as I can't find a pattern that causes it.

Thank you,
Scott

Originally Posted by Rivmage

Hi all,

So, I've had my 1998 GP GT for 3 weeks now. It has about 143k miles on it. The issue I am having is the temp will spike high, near the red zone but, the temp warning light never comes on, on every three or four drives if it doesn't sit for a few hours. It doesn't matter the time of day, I've had it happen in the morning at 60, mid-day at 95+ or evening in the low 80's, also the style of driving doesn't seem to effect it, it has happened in stop and go as well as on the highway. This past weekend I replaced the tstat with 195 tstat and the radiator cap, bled the system and filled up the coolant, there are no visible leaks. From Sunday through Wednesday the issue seemed to be solved and has been running 10 to 15 degrees cooler.

So, on my way to work this morning the car never went about 195. Went home on my lunch break to pick up something for work, the temp went to 205. I was at home for 1/2 hour and left to go back to work. About ten minutes into my 15 minute trip to work, the gauge climbs to just outside of the redzone. I turn on the heat and the temp falls back into the 210 range in a couple of minutes. When I get to work I pop the hood and I see both fans running (Air off), while the gauge reads 195-200 range.

This one has me scratching my head as I can't find a pattern that causes it.

Thank you,
Scott

Scott,

If you want to see if this is an electrical problem you are going to need a DVOM, Digital Volt/Ohm meter.
If you don't have one then clean the grounds at the battery and the ground cable from the engine to the firewall.
If you are using the voltmeter then set the meter to Volts DC
Engine running
Take the black lead of the meter and put it to the battery Negative
Then take the Red lead and touch the engine. (valve cover, or metal bracket, or Alternator) Something metal
What is the Voltage reading?
It should be less than .1V = this is 100 milivolts
If it reads something like .450V = this is 450 milivolts (Electrically WAY too high)
Clean the battery and engine grounds and see if this voltage comes down.

Why??
Electricity is lazy and will find the simplist path to ground. The path is through the water in the engine.
If you pass a current through water lone enough it will heat up.

A poor ground can cause the GAUGE to read high but the motor is not hot. I see this problem alot with almost ALL German Cars, Korean Imports and Cadillac Catera.


Hope this helps

Randy & Jill
3800GEN2GPGT

ASE Master Tech
ASE MAster Machinist
L1 Certified

Sounds like a bad coolant temp sensor. It's located in the LIM under the thermostat neck.