6.5L temperature issues

[Jle1208]

I recently bout a 1994 Chevrolet 3500 6.5L diesel. For some reason my “low coolant” light will come on. And my temp gauge stays about a 1/4 way. An will rise at times to full hot but with in two seconds it will go back down to 1/4 way. Heat blows great. My second issue is I am having white smoke coming out of my dipstick while the engine is running. It will only blow white smoke at startup from the exhaust then nothing. Runs great. Has 114k miles on it. I’m not big on diesel motors but can definitely fix anything with some directions or tips.

[Robyn]

If you are adding coolant and in a short the light is back on you likely have an internal coolant leak.

Take a look at the oil and see if it's gray and sloppy looking.

[Jle1208]

If you are adding coolant and in a short the light is back on you likely have an internal coolant leak.

Take a look at the oil and see if it's gray and sloppy looking.

Oil looks good, I just filled the coolant. Took only about 1/2 a gallon so it seems to be holding. Haven’t seen any leaks it all. Even when it is parked over night.

[Robyn]

Start the rig and allow it to warm up with the hood up.

Observe the top radiator hose and see if it gets HARD while the engine is warming up.

I it gets hard it means there is a head gasket/combustion leak.

A small leak will go by somewhat unnoticed for a time.

The temp should rise steadily and level off at about 190/210 and not pin the gauge and then fall.

Could be a goofy T stat too.

See what shakes out.

[Jle1208]

I will try that as soon as I get home to see if the hose gets hard. I was thinking maybe a sticky thermostat as well, I am going to buy one just too try out. Other than that it may be a issue with the white smoke coming from my dipstick. While the truck is running.

[trbankii]

I'm dealing with a similar issue with my '94 Yukon - low coolant light comes on with coolant at normal levels and no overheating issues. If I mess with the wires going to the sensor, it usually goes off but comes back on again in a day or two.

I need to pull the recovery tank to see if I can get better access to the sensor and wires to see what is going on.