jc33

im once again trying to fix an intake manifold leak at the rear of the block. I have taken this damn intake off 4 times and have even replaced it with another used one. It still pours upon hard acceleration. The only solution i can think of is putting a rubber rail in between the block and mani. instead if just silicone. Any one else have this problem, I need some advice.

89 Iroc Conv.

I have always had good luck with silicone on the front and rear of the intake manifold if you put just enough for it to squish out from between the block and the intake it should seal. You may have another problem I would check the oil pressure sending unit it should be located on the block next to where the intake seals if it leaking it could look ad if the intake is leaking.

Blown 346

iTrader: (12)

I agree, I had the same problem with my 91 Z. You have to use a decnet of RTV, dont be scared to use it. I filled up the whole section(width wise) of the front and back of the block with it, and had it about a quarter inch high. That sealed it up.

HD4mula

I got bite by this twice. Like mentioned yo need a really good amount of RTV and make sure that the corners at the top (manifold & head) and at bottom (block, manifold & head) are well covered. Oil will seep thru those corners and run underneath between head and block and from there to someplace and then down to floor. Many times I thought I had a timing cover leak or some weird valve cover leak but always has been out of those corners.

89Nighthawk

I always use the rubber gaskets and put RTV at the 4 corners of the rubber gaskets. I've never had a problem.

D's89IROCZ

I hear if you layer it . Like lay beads of it along the surface of the block ...let it tak up a bit ...then lay more beads on top of them ( stack them like a pyramid ) ...then you should be good to go .

jc33

Thanks for the info, i was wondering if there might be something with the oil pump or oil passages, maybe the relief in the pump is stopped up or something and its shooting high pressures at the rear manifold. I have an oil press guage though and there are not any abnormal oil pressures.

one other thing i almost forgot about, once when i changed the trans i discovered that the rear main seal housing to block gasket was blown out like extreme pressure had blown it apart, any ideas whats up with that. could that be related???

Blown 346

iTrader: (12)

If that gasket was blown out then that is where the oil is coming from. There is alot of crankcase pressure there and oil will spew out if thre gasket isnt replaced.

steve88iroc

What about the circular gasket on the bottom of the distributor? Have you checked that?

Steve

Steve Mack

iTrader: (5)

O.K.Jc33 here's the problem with the leak in the back of the intake manifold .Turn it upside down and take a look at the back of the intake where its supposed to seal .You will see the part where it is made to clear the oil pressure sending unit GM made less than half the thickness of the rest of the sealing surface .In order to get it to seal you have to really clean the surface of the back of the block.Use fine sand paper and carb cleaner then you need to use Mr gasket Right Stuff gasket maker .It comes in a can.Now comes the most important part .When you go to put the intake back on it can be moved forward or backward a little .Make sure after you put the intake bolts in you move the intake rearward. This will give you a little more sealing surface.This fixed my leak.