Engine temp (Page 1/1)
Rhodesia1977 MAY 09, 06:36 PM
I have an 86 GT with about 90,000 miles on it. A couple of months ago I was driving and the engine overheated. Turns out my t stat broke in the closed position. Normal engine running temp used to be about 190. Installed a new SAFE t stat from AutoZone and replaced coolant. Now the normal engine temp according to my laser thermometer reading at the base of the coolant gauge sensor is 245. It never goes past this. The temp gauge does move around a tad but before it stayed in the 190ish range. The radiator fan does come on. It is wired for demand use and I usually keep it on. Is this new 240 too hot? Any ideas of why the normal temp increased? Both outgoing and incoming radiator hoses get hot and the heat works fine. Any suggestions would be appreciated! Thank you!
Patrick MAY 09, 06:56 PM

quote
Originally posted by Rhodesia1977:

...according to my laser thermometer reading at the base of the coolant gauge sensor is 245 ...the heat works fine.



I bet it does!

What was the temperature rating of the new thermostat? (The factory specified temp is 195°.)

Where's the coolant level in the reservoir when the engine is cold?

[This message has been edited by Patrick (edited 05-09-2023).]

Rhodesia1977 MAY 09, 10:18 PM
Hey Patrick thanks for your input. I'm not sure on temp of t stat. All I know is that it's one of those fail safe ones. Do you think a different t stat would be better? The coolant reservoir fills most times after car is turned off. It takes awhile. A few times lately the tank level was halfway and didn't seem to go back up after car is shut down. I just think 240ish might damage the engine. Just wanted to hear the thoughts of more experienced Fiero owners. Thanks for you input!
Patrick MAY 10, 12:53 AM

quote
Originally posted by Rhodesia1977:

The coolant reservoir fills most times after car is turned off. It takes awhile. A few times lately the tank level was halfway and didn't seem to go back up after car is shut down.



That doesn't really answer my question.


quote
Originally posted by Patrick:

Where's the coolant level in the reservoir when the engine is cold?



Coolant gets drawn back into the system from the reservoir when the engine cools down. Coolant in the reservoir needs to be up to the COLD level when cold. If your reservoir is being sucked dry when the system cools down, then air gets drawn into the system. You don't want that. Air in the cooling system can lead to overheating.

You may wish to follow the method I use to "burp" the system.
theogre MAY 10, 02:25 PM
First... Top post is using the "laser" temp unit wrong. Pointed at outside of sender/sensor never shows Coolant temp but whatever metal at that point and often reads way higher.

Other contact meters using thermistors etc have same problem.

Try pointing/contact the tool at T-stat house/tube. Thin metal reads more true for coolant flowing thru there.

see https://web.archive.org/web...cast.net/~fierocave/ IR thermometer

2. Temp and other gauge using Resistive senders in the car often lies.
just 1 Example: see http://www.fiero.nl/forum/Forum2/HTML/146784.html

Need "Real" Coolant Temp while driving etc then need ECM scan tool that get data the ECM sees including Coolant temp.
ECM sensors are much more reliable because how most are wired.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Vintage-Nut MAY 10, 02:57 PM
If you doubt the coolant temperature gauge accuracy, you can test it with the appropriate resistors.
Rhodesia1977 MAY 12, 09:08 AM
Thanks Ogre, this makes more sense. I could of sworn that someone here told me to point laser temp at the base of the coolant sensor. It says 245. I have taken the temp the t stat base, metal t stat cap, and upper radiator hose and they all say a range from 170-190. So those are more accurate readings than taking a measurement from the coolant sensor base? Thanks!