When I dropped a LT1 cam into my car I had to change my intake manifold gasket. Well shortly after it began leaking oil.
So I changed the gasket again, a few months later, because I was losing a quart of oil every 1 1/2 to 2 weeks. It stopped the leak for a few days, but it came back. So I did it again, making sure to do everything perfectly, cleaning it and I got the best gasket I could find and the best RTV I could find. And finally it stopped leaking completely. Two days later, it begins to slowly leak out again. Now it's at full speed leak again. It's coming out around the back passenger side of the intake.
I'm positive I did everything right with the cleaning, applying the gasket, and the torque for the bolts.
Any ideas why this would be happening?
Thanks

 

The only possibilities that I can think of is it is leaking from your distributor and finding it's way down so it appears to be coming from your manifold or maybe there is a leak in the head gasket near the the manifold mating surface on the rear of the block. You know where the RTV meets the actual intake gasket. Just some possibilities.

 

I know what you mean. But I replace the distributor gasket everytime I replace the intake gasket, and it never has oil on it. It's always dry. I'm pretty sure you are right about it leaking through the rtv on the back, I just don't know why. How does the oil push it's way past everything? I know there is pressure, but it works fine for a few days, then slowly starts coming back out. The RTV is the blue stuff and is supposed to be oil resistant.

 

There is no pressure trying to push oil out of there. Your PCV system should in fact be keeping a slight vacuum in the crankcase.

Improper assembly is about the only possibility.

Use "ultra black" or "ultra grey" RTV. Smear a layer of it on the block, and on the intake; make sure there's some down into the corners where the heads and block come together; and smear the gaskets around the coolant passages and up the ends a little ways. Lay a bead about ¼" thick on the block, paying careful attention to where you put it, such that it's exactly where the intake will be (hard to eyeball, you might want to mark it before you lay your bead); let it cure for an hour or so, just enough to skin over a bit but not harden; then lay the intake on it, setting it down perfectly straight, and once it's in place, work it around just a bit to smear the bead of RTV onto the intake. Check the gasket bolt holes and make sure they're lined up. Let it sit like that for another hour or so, until it starts to harden just a little, then tighten the bolts starting at the inside of the intake (correct torque sequence). Let the engine sit for 24 hours before starting it.

 

I use the red pematex high temp RTV but I don't think that is your problem. Make sure that your PCV system is working fine cause if not you will build too much pressure in the crank case from excess blowby. Just another possibility.

 

Thanks guys, I'll replace it one more time. And I will check the PCV as well.

 

This is where I meant about the head gasket leak. sorry I know it's a crude drawing.

 

i used a zig zag pattern with the RTV on the back and front of the block from head to head last time i had the intake out. it worked after many times doing this job and never getting it to seal right.

 

My guess would be tightening out of sequence caused leakage. If you did it in sequence did you recheck the torque after the engine was warmed up? You should snug all bolts to 20lbs then snug in 5lb increments working your way from the center out. Proper torque is 30lbs. I only use high tack on the gaskets and on the ends front and back I use ultra black RTV with at least a 1/4" bead. Nothing else. I dont use the gaskets on the ends that come with intake gaskets. They are junk.

 

I'm sure I have the exact same leak that you do. In fact, it occurred just after I put my cam in!

Anyway, have you done a compression or leak down test? Many people seem to have this same problem and it almost never gets resolved. I'm wondering if a head gasket could be leaking into the lifter valley and popping the manifold gasket.
It's just a theory. I'm not fixing mine until it actually warms up!
!

 

I assume thread sealer was used on all the intake bolts?

It's happened to me....twice. Oil wicking up the intake bolt threads. Just a thought.

 

It's probably not the intake at all. It's probably the oil sending unit. They go bad and start leaking all the time.

 

he could have rtv in a bolt hole or two. it will look like it's fully seated but, that little bit will allow the gasket to fail and start leaking



belive me it happens more often then people think