I am about to drop my cradle (again) to fix a coolant leak that appears to be coming from between the timing cover and engine block where the coolant passes through into the water pump. It is on the front side of the engine a little above and behind the water pump snorkel that goes down to the coolant tube on the passenger side. This is the second time it has started to leak here. The last time was about 3 years ago. This is a Grooms 3.4L rebuilt engine that I got used from Ed Parks. Here are my questions:

1) What could be causing this?
2) Is this common to this engine?
3) Any thoughts on the best sealant to use so I don't have to do this again?

Thanks, I just want to get this fixed for good and I'm looking for ideas.

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If the water pump was at one point replaced, then there is high possibility that the front main seal may be where the leak is at. Due to design, if the water pump is serviced for whatever reason care has to be taken to ensure that the front main seal on the timing cover is not damaged. This can be difficult to accomplish, even with brackets that are typically installed to secure the timing cover when replacing or servicing the water pump. It could also simply be leaking due to age, which isn't uncommon, or potentially due to improper coolant service life.

I would also check the actual passenger side coolant hose where it attaches to the lower side of the timing cover area in the front of the engine, simply because it may be worn out and causing coolant to leak past where it seals.

Ultimately, you will probably have to pull off the water pump & the timing cover and properly re-seal them all. Just use a quality Fel-Pro gasket set (nothing cork) with a good quality RTV like Permatex. Since you will have the cradle dropped it would also be a tremendously opportune time to thoroughly clean everything in that area good - I would do it before I disassembled the timing cover. Then clean the matting surfaces up good and do a final clean on all the components. It would also be a good time to just get a new water pump, since they only run around $25.

[This message has been edited by Fiero84Freak (edited 12-22-2013).]

Thanks, I think you have helped me figure out how it happened. I probably damaged the seal when I changed the water pump a couple of months ago which I forgot to mention above. One other thing that has me wondering is that it only seems to leak when it has been ran for a good amount of time. Could this be because the opening needs to really heated up to expand enough to leak?

Yeah I actually have a similar issue right now with my current GT (I need to do the same thing you're doing, but mine is because of the utterly high mileage my Fiero has) and have seen this type symptom in the past. I'm guessing what you're seeing is you'll drive the car for a bit, it'll warm to operating temperature, you'll park it, then you'll get a minor coolant leak, but then it won't leak any more after.

I think your guess is pretty accurate. Since coolant/water is circulating, then it warms up, the leaks are likely around the areas of the timing cover that see coolant pass. So there's a minor leak, then the car cools down, no coolant is running through, then all of a sudden it's like there's no longer a leak.

I think I have found the leak and it is not where I thought. I think it is/was coming from the upper hose where it connects to the crossover pipe. No way to see it while it was in the car because it was behind the engine and among a nest of wires etc. It also makes sense that it wouldn't leak until the engine was very warm and the thermostat open. When the thermostat was closed the coolant doesn't flow through the tube. Maybe this will help someone else.

I am going to clean up a few things and do some other general maintenance, maybe port the exhaust manifolds while I have it out.