Water Temp Gauge problem - HELP!

Im leaning with the others. I was thinking of the old muscle V8s when low of fluid for cooling the sensor in top center pipe of the block would bounce around as the fluid rose and fell inside that pipe. But today's trucks introduce a whole another world of potential problems.

One time with Dowdy my FLD 120 had trouble with gauge and ultimately the sensor probe itself deep in the block was actually corroded or rusted beyond being able to accurately read. So that settled that.

Another time with a 350 cat refusing to behave with it's water temp turned out the radiator cap failed to hold pressure and was bad. No pressure no cooling.

Combined with that I follow the Pyrometer and engine oil temp and pressures as well, but there is no point getting into all that with the choir here.

 

Mine was a combo of issues, the main one I THOUGHT we had addressed. The main thing, I came to find out later, a mechanic at my preferred shop never really blew out the radiator and condenser in front grill...even though he swears he did...THAT caused a LOT of pain doing other things that were unnecessary. I suspected all along the motor wasn't breathing properly. Simple test, put a shop rag in front of the radiator when the fan is on....it should stick due to the suction. If not, you need to blow the radiator and other things in front out with an air hose. Just be careful not to bend the fins of the radiator.

The other issue was a bad temp sensor and a bad guage.

I also changed out the stock 190 T stats and put in Pittsburgh Power 180 degree T stats (Detroit has 2). The issue with the OEM Detroit T stats were, they only just START to open at 190 and then don't fully open until it gets to 205...the fan comes on at 208, and the check engine light at around 217 or 218. so, we were constantly bumping up against it in the warm weather! The winter before, no problem with overheat. But, last summer, constantly fighting it.

The Pittsburgh Power T Stats are OPEN at whatever temp they claim (I think mine are 180)...you can watch the temp gauge, especially when the T stats first open on a cold day....temp gets to 180, T stats open, cold water dumps into block from radiator, temp will go back down to 150. Eventually, the water warms up enough, system evens out, but, it is cool to watch, know that they are working!

Good luck with it, please, let us know what you find out was the problem!

 

Oh, and one other change I made...my Intl 9200 originally had a Cat in it, was replaced with a Det 12.7 about 5 years ago. The cap was a 10 lb-er. Detroit says it should be between 16-20. I had it pressure tested at International to 25 lbs and put on a 16 lb cap.

Again, good luck. Let us know what fixes it.

 

1996 frightliner fld 120 temp goes from 100 to 200 while on cruise control or going up a hill. If I take my foot off the pedal it goes back to normal. Shut off light appeared for a second then turn off have no clue what's going on