I have a 98 B3500 1 ton van that is overheating. It started by just losing a small amount of coolant and I could hear a hissing sound. It went from there to completely boiling over. The van sat for a year, and now I have been driving it every now and then. I am thinking that the thermostat might be stuck in the closed position. It has a 5.9L motor. What do I have to do to change, or at least look at the thermostat? Thanks.

 

The upper radiator hose leads to the thermostat cover. Drain your coolant and remove the thermo cover end of the hose. Then remove the bolts that hold the thermo cover to the intake manifold and you will gain access to the thermostat. While you are up there be sure to check the heater core hose that connects to the intake manifold neat the thermo cover for leaks.

If your thermo is bad be sure to replace it with a modern style thermo that is designed to fail (if it ever fails) in the open position.

 

I have one of those Fail Safes Thermostats in my 1977 Impala and it works very well. I do like the fact that if it does fail that it will fail open. When it is time I will install one in my 97 B2500 van.

While you are changing the thermostate be sure to look for any evidence of leakage from the water pump or other hoses as well.

 

It was more complicated in my 96 B3500. There are many bolts to remove as you have to remove the alternator and A/C compressor out of the way, plus take the dog house off to get at a brace that goes to the alternator. Only once you get that out of the way do you have enough room to get to the thermostat. I guess all-told it took me a couple of hours, so not horrible.