Engine/Transmission (1994 - 1998) 12v engine temps?

[snowracer69]

Hey all,



A friend has a '97 undervalved truck, and I first got to ride in it last weekend. He's put a plate in (#6 I believe), valve spring kit, governing spring kit (I believe that's what ya'll call it), and he straight-piped it. When I drove it, I noticed that his engine temp sits just off the bottom, around 140* or so. My '01 runs either right at 190* or just above all the time, not matter how I drive it. I told him I thought he had a bad temp sensor or thermostat, but the temperature did change, so I still think it's the thermostat...



Question: What temp should this truck be running? Obviously if its too low, it could have a bad effect on fuel mileage... should he throw a 180* t-stat at it, or 190*?



Thanks for any help, and please excuse my 12v ignorance.



Josh.

 

[Kirwin]

Whos got an undervalved truck?

I have installed a Cyberdyne digital temperature gauge that stays with in 10 F of 180 F. The only fluctuation on my 97 is when the thermostat first opens the installed gauge goes from approximately 190 F all the way down to about 145 F. Then it slowly climbs back up and is rock steady at about 180 F. It does rise on long pulls with the trailer behind and I have seen it over 200 F when pulling long hills. Some trucks cycle between 145 F and 190 F all the time though. Tell your buddy to spend the money and buy a Cyberdyne digital gauge form Jeggs High performance and see what the says before you do anything else. Its an easy install and a very high quality unit. you can use the Isspro gauge cup from Geno's or many other mountings. By the way the stock thermostat is 180 F.

 

[illflem]

It's very common on 12 valves for the gasket that goes around the stat to come off and get stuck keeping the stat from closing. Most times you can just put the gasket back in place without replacing anything. Some folks just toss the gasket, it isn't really needed.

 

[Deezul1]

The stat is bad. Been there twice on 2 different trucks. It should run about 180-190 and depending on the stat may cycle from 140 to 180 back and forth constantly which is normal. When mine stuck open the gauge hardly moved from cold.

 

[BWilson]

I have over 400K on my truck and the temp gage almost always is around 140-150. Sometimes it will rise up, hit the mark (180 I think) and fall back down to around 140-150. Nothing is wrong.



And like my Gramps always says, "If it ain't broke, don't fix it!!!"

 

[Deezul1]

BWilson

Before my most recent stat replacment it always ran about 180 with the cycling mentioned above. I replaced the stat with the correct PT# Cummins stat to stop the cycling and it never got over 150deg. I removed that stat and put in a NAPA stat and it went back to cycling up to 180-190 for a while and now its back to never getting above 150 or so but then ever once in a while will go up to 180 again. These stats are sure strange, I am getting tired of changing them trying to get it working right. It takes too long to warmup in the morning with the current stat even when plugged in. I know I am a wuss about cold but thats why I no longer live in Alaska or Idaho anymore.

 

[C. Harlan]

mine, with 171,000k never goes over 185° in the summer... the hottest I have had it was 215° pulling a heavy load in 4th gear. She usually stays about 170-180°, but never runs hot at all.



-Chris-