02 4.6 coolant leak

[66stingray]

I was wondering if anyone can give me some fresh ideas regarding my coolant leak. I have ruled out radiator, expansion tank, water pump and even the thermostat housing as a possible culprit. The leak is coming from the rear of the engine. After jacking the truck up and taking a light to the underside, i have a drip that is right in the middle of where the oilpan and transmission housing meet. It doesnt appear to be dripping from anywhere else or migrating to that area, at least that I can see. I also checked the heater hoses on the firewall and the one hose that goes to the iac housing, nothing. The only thing im thinking at this point is that the intake manifold has a leak at the rear down low where i cant see or a head gasket is leaking in the rear, again that i cant see. Any alternate ideas? The leak is weird as well, it can drip pretty good, stops and then would start up again. Only drips while engine running.

 

[fordysenior]

I was thinking it sounds like the intake manifold -- is it the stock one, or has it been replaced?

 

[66stingray]

Stock manifold. Theres so much crap at the back, hoses, connectors, etc. that its hard for me to even get a small mirror to see anything.

 

[fordysenior]

My 2002 is an early build, yours may be different.

If I remember right, there is a metal casting in the back in the way of any view. That casting has a hole drilled about 3/4 inch size to allow draining from the top of the block. The hole is right in the center. My 4.6L had a plastic passageway from the thermostat and it went around the alternator to the other side. Other intake manifolds have a metal passageway, the rest of the manifold is plastic -- including Dorman aftermarket units. There are plenty of threads on here on repair tips if you do a search.

 

[Joe in NY]

It could also be the pipe that goes under the intake manifold to the back of the water pump. This is the return for your heater core

 

[66stingray]

Thanks for everyones replies. I will look into the suggestions. My Haynes manual doesnt have a cooling diagram so kind of getting bits and pieces from the web.

 

[lincolnshibuya]

if your intake manifold is stock then it's likely the source of leak, mine leaked around 90k+ miles and I see coolant traces near the bellhousing (just like your case) replaced mine with Dorman intake and no leaks..

 

[66stingray]

167k miles on stock. Guess its overdue, lol