I have an unusual coolant leak. Seems to be leaking from somewhere under the thermostat on the passenger side sort of beside the oil filter. I can't even tell exactly where it's leaking.

It started to leak shortly after I pressure washed the engine (I'm yet to be convinced that's why it's leaking but I don't know). The weird thing about the leak is that it comes and goes as it wishes. One day it will leak a gallon of coolant and then it won't leak for a week. It would seem to me the leak is happening from higher up on the engine because after so much leaks out it sorta (more or less anyways) stops leaking.

Ideas? I don't think it's the head gasket but it might be, I don't know. I don't seem to have coolant in the oil or oil in the coolant. Both seem fine.

 

Check the water pump...

 

ive had them leak externally from the head gasket right above the oil cooler/filter mount. only would do it when i worked it hard , drove 2 months that way. never mixed oil and coolant or lost performance,external leak only,look closely in that arrea for a streak down the block.

 

I don't know if your truck has the same plumbing for the Auto Tranny but mine had a port under the t-stat housing for the tranny cooler. I think it was a 1/2 inch pipe fitting to hose. I assume yours is the 4spd tranny, may or may not be the same, just an idea.

 

oh, and when the truck leaks, it leaks when it's not running as well as when it's running. Then other times it won't leak at all.

 

sounds more like hose or gasket.probably not head gasket luckily

 

I don't think it's a hose, that would have been pretty obvious I would think. I was thinking a gasket too or something loosened off but I can't tell where it's coming from exactly. Apart from the thermostat, a couple hoses and the water pump I don't even know what is there to leak though.

 

Have you checked the oil cooler? It's the plate that the oil filter mount is attached to. There's maybe a dozen or so 10mm bolts holding it in place. I had a sporadic coolant leak on my 92 over the summer in the same area and it turned out the oil cooler mounting bolts had worked loose.

 

Apparently the 5.9BT had a problem with leaks in the head gasket in the front corner. Mine has leaked so much that it looks like Carlsbad Caverns down the block!

 

Been there....And understand...