Why my intake leaked

[Pete Munroe]

Olddog,

Leaks are ALWAYS a pain and frustration...!

I doubt it was the RTV.

The gaskets, compostion, what ever are pretty solid compared to RTV.

The RTV comes out of the tube pliant...liquid to gel...seems unless the assembler waited for the RTV to pertify, it will squeeze out before the gasket.

I have aluminum heads, iron block.

My intake manifold gaskets failed after 3000 miles...it was I think due to not re-torgueing the intake bolts.

The gaskets...Fel-Pro super something or other...looked like tortured snakes around the ports...but the RTV BEADS at the front, rear, and around the water ports looked to be fine.

Now, how could a semi-liquid-gel-paste RTV could support the manifold higher than the composite gaskets under 22 ft/lbs of torque?

After I replaced the gaskets at 3000 miles, 500 miles later I had a rear manifold oil leak...because I did NOT use ENOUGH RTV to get a solid bead across the rear of the manifold/block interface.

Now, I do re-torque the intake every oil change or so...more often actually...Have 10,000 more miles since the LAST gasket change and no leaks.

Intake gaskets for me have proved to require re-torquing...often.

Pete

[olddog]

Originally Posted by Pete Munroe

The RTV comes out of the tube pliant...liquid to gel...seems unless the assembler waited for the RTV to pertify, it will squeeze out before the gasket.

Pete, I am not an expert or I wouldn't be asking for help on this forrum, so don't take me wrong.

I have worked in the plastic industry for 30 yrs. Molton plastic at the right temp is very similar in viscosity to RTV. We assemble some piping that is 5" ID with a piece of aluminum for a gasket. The seal surface is a 3/4" irous. There are 10 studs that are 1.25" diameter. These studs are torqued to 3000 ft-lb. If we allow a tiny drop of polymer to get on the gasket, it will have a slow leak forever. No matter what you do, you can never squeeze it out.

Where the RTV was on the gasket on both sides, I was measuring 0.010" + thicker than where the RTV was not. I had cleaned the RTV off the other gasket and it measured about 0.005" thinner where the RTV was than the rest of the gasket. So the gasket compressed more where the RTV was. I have no doubt the RTV was holding the intake up at the four corners, and most of the clamping force was going to the RTV areas.

The milled out area where the bolt goes between the ports, was level full with oil. I don't think this area had much clamping force at all.