strange coolant leak on my 3.8

[Mister DNA]

I drove my car hard for a few minutes before getting home and when I stopped, I smelled coolant burning. Popped the hood and saw fast drips coming from the area under the throttle body where you can see the lower intake joins up with the engine block. But the leak wasn't from there. After cool down and a refill, I started back up and the leak was a fast stream that appeared to be coming from under the upper intake and dripping down the back of the spot where our engines have the thermostat mounted in that isolated section of the intakes. Not sure where exactly, though.

I put some stop leak (with the powdered aluminum and the fuzzies) in and it has slowed to almost nothing but that's just temporary. I want to get in there and pull the intakes off, but I want to see if any fellow members have had this problem so I know what I'm getting into before I'm way over my head. I know I'll see the stop leak stuff in the area of the leak, but I'm not about to pull my intakes off if that's not the problem.

I checked my oil and I don't have a crankcase full of chocolate pudding. I do, however have jelly-like stuff on the underside of my radiator cap that looks a little like oil but doesn't feel oily at all. That has been there since I got the car, though.

How easy is it to pull the intakes and put new gaskets on? I have to change my serpentine belt anyway so I could get right down in there if I had to since the alternator and tensioner bracket can just come off at that point.

[Mister DNA]

Looks like it's that elbow piece. For all interested parties, the GM part # for that piece is # 24503423

[hockeyman]

Elbow piece? You mean the thermostat housing?
If it's cracked, then either have it welded at a shop or replace it altogether.
That brown gel you are referring to under the radiator cap is from the DexCool Coolant...It's sh*tty stuff! I switched to the green coolant last year, and the brown muck is no longer haunting me.
Look here for a total coolant flush.

[Pewter2K1]

there are 2 plastic rubber 90* tubes that go from the waterpump/front cover assembly. those things tend to wear out.. they cost like 4 bucks a piece, but i think the intakes have to come off to change them.. i changed mine when i did the cam, so they were off anywyas

[brink]

I think its a intake mandifold gasket that situation sounds just like mine did..

[Mister DNA]

It was the thermostat bypass pipe that attaches to the alternator/tensioner bracket. $8.50 at the GM parts counter. Mine was broken off at the block. I could tell this was the culprit because of the gathered stop-leak fuzzies around the broken edge.

I dug the busted piece out of the hole, cleaned the hole with an old toothbrush, repeated the process on the bracket side and put the new part in place with the o-ring seals coated in silicone grease. Drove for 75 miles to Idaho and back just to be sure and no problems.

Good to know the brown muck isn't oil-related.

This engine never fails to amaze me. 123,500 miles and still running like new. Perfect compression across the board and only this little tiny problem other than routine maintenance like the plugs and wires. I replaced the serpentine belt with a Gatorback when I did the pipe replacement. Good move. The old one was stretched way bad. Tensioner was almost to the end of its travel. Maybe that's why my AC compressor made noises like it was skipping on the belt. That can't be an easy accessory to turn when loaded. But I can't get the clutch to engage now so I'm unable to test my theory.