I'm losing coolant near top of engine, about a cup to a pint per day. Looks like it's coming from front up top like intake manifold. Is this a likely place for coolant to leak? When I get home, if I'm fast I can catch adrip or two coming from up there. Is it difficult to remove, plane, replace intake manifold? Any ideas? 96 3.8L V6.

 

Is it coming directly below the throttle body? There's a small plastic elbow that runs from the belt tensioner assembly into the lower intake manifold, right below the throttle body. It's difficult to see but if i remember right, you should be able to feel it. It's pretty common for these to crack and leak coolant as the plastic ages. To replace it:

1. Remove the two heater hoses from the belt tensioner assembly. You will need to drain some coolant first, unless you want to make a mess.
2. Remove the serpentine belt, alternator, and tensioner assembly. It's not difficult, I think the alternator and tensioner have 5 bolts combined to remove.
3. The elbow should come out with the tensioner. Go to Advance and pick up a new elbow in the HELP section. Otherwise, NAPA and the GM dealers have the part as well. Advance and NAPA have them for like $4, I think.
4. Press the new elbow into the tensioner, and reinstall. It's just a press fit. Might want to oil the O-rings to keep them from tearing or binding.
5. When everything is back together, remember to bleed your cooling system. Fill the car up, run the car until its hot, and crack open the bleeder located above the thermostat housing until you get a solid stream of coolant coming out (no bubbles). You have to wait until the car is warm or the thermostat will be closed.

Disclaimer: You *may* need to remove the upper plenum to get access to this part, it's been awhile since I did this. I was replacing all of my intake gaskets anyway and had it torn down pretty far before i realized it was this stupid little elbow. If your motor has some miles on it you might consider replacing your lower intake gaskets, as mine were pretty warped when I removed them, and I've heard this is one of the only weak points of the 3800 engine.

Also check to see if you have any "milk" on the bottom of your oil cap. If you do, you definitely need to change your lower intake gaskets and hope its not your head gaskets.

If you DO have to replace your lower intake gaskets, its a fairly involved job but if you mechanically inclined you should have no problem over a weekend. There's a couple tricky bolts to get to near the firewall and you have to remove the fuel rail, etc.

How many miles on the engine?

 

If you have to remove the plenum, make sure you take out both of the bolts that hold the thermo housing on the plenum. One of them holds the plenum down and will not allow you to lift it until it is removed.

 

Thanks Maso and os.
Yeah, looks like directly below the throttle body. I'll check for the elbow.
162,000 miles.
No milk on oil cap.
Thanks for the step by step. I'll get into it this weekend, start with the easy stuff, and go from there.

 

Here is what you are looking for. THe shinny metal is where the water pump should be.

 

photos aren't showing for some reason...

 

thanks Gorn. The photo works on my home computer. Autozone says its dealer part. Advance says I have to buy the whole belt tensioner pulley assembly $75. Couldn't find it on GM parts direct. I did get a look at the one that came with the assembly at Advance & looks like the one in the photo. Black plastic about 5/8" ID with an o-ring on each end. I'll keep looking. Any ideas?

 

I thought the intake kit came with one?

 

I'll check thanks

 

I bought one from the local chevy dealer. It's a non-stock item, so they had to order it. It's called the heater bypass pipe, and was $12. The next day, I saw one exactly like it at AutoZone for less than $5. My local store had it stocked on an endcap behind the counter, right with all the coolant caps, etc.

If your oil looks like oil then it's this part. I was in the same boat as Maso when I needed it replaced: I thought it was the intake gasket, but after I took the intake off, this pipe came out with it and the plastic was all rotten through... Crazy stupid part IMHO, but super easy to replace. Like mentioned above, just remove your alternator and tensioner.

When installing the tensioner back into place, be super careful that this pipe slides directly into place. Don't force it, or you might break the new pipe and have to buy another.

Props to Gorn for the pic! How in the world did you take that? Did you remove the TB and water pump just for a pic, or did you happen to have an extra 3800 engine lying around? LOL!