I have a 94 T-100 with a slight coolant leak under the thermostat housing. The dealer told me that the leak is actually coming from under the timing belt cover and the cover needs to be replaced. If this makes sense to anyone, please fill me in. I thought it just needed a new gasket under the thermostat housing and he's talking $400!

 

I don't see how replacing the timing belt cover would do anything. It's only there to stop things from damaging the belt. Timing belt covers don't stop leaks.
If it's really leaking from behind the timing cover that could be the water pump, it's the only thing back there with coolant in it. Personnally I would just replace the tstat gasket and see what happens.
If it is the water pump then $400 is not bad.

 

No, the timing betl cover doesn't seal anything. You need the water pump pulled and re-sealed. He is probably just using idiot public speak (you know, like instead of your rings are worn they say "your engine is toast"). It is an expensive job because they have to pull a lot of junk to get to it. If you did it your self it would cost you about $20 to get a new water pump, gasket, and theroustat. It takes a good number of hours though.

 

I spoke to the mechanic this morning and got more information. (Spoke to the service manager before.) The mechanic tells me that it's the upper water inlet that's leaking. He says this piece fits between the intake manifold and thermostat housing and passes through the idler bearing and out from under the timing cover. Anybody seen one of these before? New upper water inlet is $95 and labor is around $300. I'm going to stop buy and have him show me the actual part.

 

You have mentioned the two places that would cause a leak under then timing cover. Either the W/P or the timing belt idler would be the culprit. It is a good sized job about six hours for the first time. Probably at least five hours of labor per the book. If you decide to have them fix the leak you might want to think about having them replace the timing belt. Since they are already there.
Are you sure the water isn't running from the upper radiator hose to the front of the engine and out of the bottom of the timing cover? This is an easy fix if this is all it is. I bet though that the w/p is the weakest link.

Good luck.
D

 

If they have to take the timing cover open for that pulley with the water inlet through it, also change the timing belt, water pump, and that idler itself (even if it is just the gasket). That idler recently went bad in mine 8K miles after I had torn it down to do the timing belt. It wasn't leaking but it was vibrating badly. I had to put it in the shop because I was in school doing finals.

 

Did he say which end is leaking, if it's the outer, where the rad hose connects to, that's a simple repair. Just drain some coolant, unbolt the part the hose connects to put on some RTV sealant and bolt it back on. If it's the innner part where it bolts to the block then that's a big job. If you have to replace that part you may as well put a new timing belt on as well.

 

He didn't say which end was leaking but I'll talk to him before I do anything. I'm planning to take your advice and start with the thermostat gasket. Thanks for all the advice.

 

The thermostat and the upper water inlet are in two completely different places. Be sure you do some poking to find out EXACTLY where it is coming from before you dump some serious $$$ on the mechanic fixing it.