Coolant leak. I can't find it!

[KC10Chief]

My 91 Explorer had a few small coolant leaks recently. One was the lower radiator hose, one was the bottom of the water pump gasket, and one was one of the heater hoses. I replaced both radiator hoses, both heater hoses and the water pump. After all of that, I noticed a small leak on top of the water pump, towards the drivers side. There's an elbow there and I noticed a little bit of coolant. So, I removed the water pump again, bought a new gasket and reinstalled with the blue stuff and the sealant. I even let it sit for a few hours before I refilled the system with coolant. Now, the leak is still there. It's not a fast leak, but there's always a bit of coolant. Is there somewhere above the water pump that could leak coolant? I can't really see anything, but it's hard to tell. When standing in front of the truck, facing the engine, the leak is coming from the right (driver) side of the water pump housing. That is, if it is coming from above the water pump housing somewhere. Any ideas? Are there any sensors or anything up there that could leak?

 

[Maniak]

You have the upper intake that could leak (doubt it, but possible)..
There are 2 coolant sensors on the intake at the front, one for the dash and one for the computer (dash one only has 1 wire).

Also, the heater hose connection on the upper intake has been known to rust. That means you need to push the radiator hose down farther until you can change out the connection on the intake.

Thermostat housing is also higher than the water pump and has an o-ring to seal the thermostat. If you pinch it, it will leak.

Those are the only things above the water pump I can think of on a 1st gen.

~Mark

 

[KC10Chief]

Well, I found the coolant sensors that you mentioned and they don't appear to be leaking. I wiped it down tonight and stared at the water pump for about 15 minutes while it warmed up. It appears to be leaking from the water pump gasket. It is a very slow leak and it doesn't appear to be coming from anywhere else. It's coming from the top of the water pump gasket, just to the drivers side of the water pump housing. There's a little elbow there. This is the same place it was leaking last time. Am I doing something wrong when I put this thing in? I used a lot of that blue stuff sealant. The leak is a lot slower this time than it was last time. Any ideas?

 

[KC10Chief]

Also, I don't know why, but it appears that I put this thread in the 95-01 Explorer forum. Mine is a 91. Can a mod move it to the 91-94 forum please?