I do not see any leaks while the truck is running, and it does not pool until the truck sits overnight. I believe the engine is newer (late 80's early 90's). I can't find any wetness on any of the hoses, just a pool of coolant sitting on the water pump towards the drivers side. If the gasket for the timing chain cover is bad, would it seep out while the truck sits, but not leak while the truck is running?

 

If it's pooling there the leak has to be above it. Drain the system and remove the upper hose from the t-stat housing. I bet you'll find the area that the hose was clamped to is all corroded and there are small holes in it. If so buy a 180* t-stat, housing, gasket, and new coolant. If the stat you buy doesn't have a steam hole with a B-B covering it, drill a 1/8" hole in it. Mount the stat with that steam hole in the 12:00 position.

 

I'll take a look, but the fact that there is no wetness any where on or around the t-stat housing or connected hoses makes me question whether that could be where the leak is originating from. Couple that with the fact the that t-stat housing is on the opposite side of where the coolant is pooling, with no coolant directly under the t-stat just leaves me a bit confused. I'm left thinking the coolant is leaking from the engine through the where the timing cover meets the block. But I've run the engine to running temp and not seen any coolant leaking. Its just the next day when I look, there is a small pool of coolant.

 

Maybe from the intake. Put a paper towel on the front of the motor so it drapes over the seam between the intake and block, but does not touch the water pump. Leave it over night and check back.

 

That's a good idea. I start with the paper towel. If it stays dry, it will at least eliminate the intake as the culprit.

 

If it only happens at night, put a drop light under the hood and trick it into thinking it's daytime, poproblem solved

 

heh, funny. The paper towel stayed dry. It was pooled again and the only place above where it was pooled was the corner area where the timing cover and block meet. So, I have a timing cover gasket to replace. Despite the leak being small, I'm surprised that it didn't leak noticeably when I ran the truck for a while. Thank you all for your input.

 

One observation from a 35 year professional (?) mechanic. Ford has greatly improved the ability of their engines to hold their fluids in. It isn't uncommon to see an engine with 200K on it yet is still bone dry underneath. Just an observation. GM and Chrysler have made similar strides as well. I'm surprised my 390 that I just overhauled doesn't leak something from somewhere. I almost expected it.

 

Use a radiator pressure tester.

 

How about a few pictures so we can eye ball it.

Cold night time temps causes things to shrink a very small amount when a change in the weather at times that will cause coolant leak, also it also depends on the type of hose clamps used.

Orich