no heat - overheat ??

[TMitch]

I drove 12 miles into town last night to pick up my daughter. While in town the engine was shut down for approx 25 minutes. About 2 miles out of town on the return trip, I noticed no heat blowing and then the temp gauge started to spike. I did notice the fan running as well. I pulled over and shut it down. the rad overflow was empty. I waited 10 minutes and went back to town and filled the overflow and grabbed a couple of gallons of water. Drove home with intermittent heat and higher than normal engine temperatures but not in the red.

When I got home and it had cooled down I found it was down about one gallon of coolant . I filled it while running and ran it until it was up to temperature. The top rad hose never got warm. There is no water leaking from the water pump.

I'm going to change the thermostat, what else could it be... I haven't noticed any difference in the exhaust color and the oil looks fine. How else can I diagnose a failed head gasket?

 

[jdooner]

overheating

Sounds like you need a new thermostat.

 

[Wingate]

It sounds like you have air trapped below the thermostat.

If the coolant gets low enough, then you re-fill it, you can actually trap air below the thermostat. With air trapped there, the engine can overheat due to the thermostat never opening. You might try and find a place to purge the air below the thermostat and run it again...

Could the source of the initial coolant leak be the pesky hose/clamps behind the turbo?

Just a thought. .

 

[jelag]

I don't think I'd do a thing until the system settled back down and you got all the air out and have a chance to see what's going on... . I own several of these trucks and have yet to see a thermostat go bad...

Everything you describe in your first paragraph is the sign of low coolant, which you've now taken care of... . its time to let the air settle out and look for leaks...

BTW we always add back only distilled water when we add coolant and water...

 

[TMitch]

thanks for the replies

I called my mechanic and he told me to check the hose clamps back by the turbo because they can have very slow leaks and lead to the exact symptoms that my truck displayed and it is as Wingate and Jelag say... coolant got low and now that the air has settled out it is back to normal. There are no signs of current leaks but I will watch closely. Thanks for the timely replies...