99 GT: Coolant Leaks

[eippermx]

I think after 200k miles on my Flaming Tomato, its starting to want a little more TLC than usual. Pressure tested the 3.8 (pumped 16 lbs of pressure several times due to the severity of the problem) and saw the following:
1. Water weeping from the elbow. (Lots of threads on this subject)
2. Looking straight down, chest facing front on the engine, coolant landing on the passenger side axle.
3. Heard air escaping. Found bubbles behind the T-stat housing along the lip of the UIM.
4. Checked the rear of the engine. Line of water from along the backside of the T-body down to where the tranny mates and it works it way down the backside of the engine towards the firewall.
Note: The elbow I believe is a coincidental issue. The leak is very tiny in nature.
Question(s):
1. Am I looking at a warped UIM? If so, what manufacturer would you recommend for a replacement unit? OEM? Aftermarket (who) ?
2. Is the UIM wet intake manifold? If not, am I looking at LIM manifold issue?

[BNaylor]

Originally Posted by eippermx

Question(s):
1. Am I looking at a warped UIM? If so, what manufacturer would you recommend for a replacement unit? OEM? Aftermarket (who) ?
2. Is the UIM wet intake manifold? If not, am I looking at LIM manifold issue?

Possible. Remove it and inspect it. Either Dorman or APN. Both are good.

UIM is a wet intake manifold with coolant passages to the throttle body.

UIM leaking issue could just be the gasket including the one at the throttle body.

[richtazz]

Since it's a known issue, I'd also replace the LIM gaskets while you have it torn down. Not much more money ($45 or so for the LIM gasket set) or work (just a few more bolts) while it's torn down, and no sense doing this job again. On whether it's a gasket or warped LIM, as bnaylor stated, you'll have to inspect it. 99 was the changeover year, and your car could have the improved UIM, and that would mean the gasket is most likely the issue. If you have the older design UIM, then it's the issue. Look for deformation around the EGR stovepipe that comes up from the LIM.

[eippermx]

Thanks Bob & Rich. I'll plan on swapping out the LIM gaskets with the GM steel ones and install an APN UIM. Cripes while I'm at it, might as well go through the entire cooling system, R & R the water pump, hoses, T-stat, and have the radiator rodded and cleaned.

Once again, mucho gracias for your advice!