B4000: Repeated Thermostat Failure

[Stereodoc]

My B4000 keeps eating thermostats. I purge all the air out and the recovery system is working but every month or so the t'stat sticks and the engine boils over.

98 B4000 w/ 4.0L AT

 

[adsm08]

Are you changing the coolant?

Are you sure the rad isn't plugged?

Are you sure the water pump is working?

 

[Stereodoc]

Yes, radiator and pump are working. Rad is hot on one side warm on the other. Without a t'stat engine is cold. When the t'stat is working it maintains temp at 195. Initially the recovery system wasn't working. It would push coolant out but not pull it back in so the system would go low. Fix that so coolant in the tank would go up and down as it's supposed to when hot and cold. Coolant has been replaced twice. But everyonce in a while the system pushes a large amount of coolant out to the tank or it boils over.

When it did this last week the t'stat was locked, upper radiator hose was collapsed. Engine got hot enough that I could hear the t'stat pop open. I had the radiator cap off and I could hear a whoosh as the coolant in the radiator was suck down.

Is it possible to have an intermittent head or manifold gasket leak and intermittently cause the coolant level in the engine to go low and create an air pocket at the t'stat?

This all started back in November after a coolant change and I've gone through 5 t'stats since.

 

[alhutch]

Are you using OEM or aftermarket t-stats?

 

[Stereodoc]

eventually I tried an OEM and for the most part it work OK but the real problem was an intermittent leak in the head gasket. It finally failed catastrophically last week on the way to work. Got stranded on the side of the road. Not happy. Truck is in the shop now.

Anyone know what it typically costs to replace a head gasket or both on a B4000 (V6)?

 

[Stereodoc]

update: Pulled the heads off. One head is cracked as well as number 1 piston. The spark plug insulator at one point broke off punching a hole in the top of the piston, not clean through but over time a crack developed from the ding in the top to the outer edge of the piston. Not pretty. Number 2 cylinder is scored and pitted. The head gaskets that came out are not OEM. So they were replaced at one point. Looking to replace the engine.