My buddy has a 2001 ZR2 Blazer with the 4.3L. Routinely takes it off road(rock crawl) and mudding. Came home the other day and noticed a puddle of coolant under the vehicle when he parked. He couldn't tell where the leak was coming from, intake, heads or cracked block(easy fix - JB Weld right?).

Last night he pulled off the intake expecting/hoping to see pieces of the intake manifold gasket missing. Apparently all the intake bolts were wet with coolant, corroded and one had some nice DexSludge in it. I guess they use a plastic/paper gasket on the sides of the engine and connect those two strips with RTV that is run along the front and rear of the engine. Jason was saying the plastic gasket that surrounds the rubber seal was cracked on both sides of the seal in numerous spots near the front of the motor, but the back was all in tack. When he pulled the intake off, half the RTV came off on the intake and the other half stayed on the block, so really no way to make sure that was the culprit. He said the coolant was dripping right from the rear corner where the intake and head meets, so it makes sense it would be from the intake instead of from the top of the head?

I know many of you guys here have had intake leaks before, so just trying to gain some knowledge here.
Thanks,
Andrew

 

Very common on the Vortecs (4.3, 5.0, 5.7)...usually at the front DS corner and rear PS corner. When I had my ZR2 and was on some of the boards, people were replacing them like crazy...bad design from GM. Mine never went bad in the 65K/5 years I had it. Must have gotten lucky. For some reason, the 4.3s seem to have more probs. w/ the dex than the other motors. Tell him to upgrade to a Stant cap, the factory one sucks and is a big reason why the Dex gets contaminated and flush all the old stuff out. if he does that, there's no reason he can't go green, but the jury's still out on whether that is better or not in the long run. The newer gaskets are much better so he shouldn't have the problem again. It's not a huge project, just time consuming...my friend is a mechanic who does stuff on the side at his house and he and I can do one in about 2-2.5 hrs., he does a ton of them, especially on the FS trucks.

 

PS rear of the intake seems to be the most common leak. I don't know what causes it, but it's one of the most common problems I see on the older generation motors.

 

Make sure you use the updated GM gaskets when you put it back together...