how do I seal o-ring?

[kcombs]

I have a antifreeze leak that looked like it was coming from the o-ring below the thermostat where the manifold between the heads attaches to the timing cover. When I got the manifold off the o-ring looked fine and I don't see any corrosion that I would expect to lead to a leak. I did a valve job on the 401 over ten years ago, but don't remember putting anything on the o-ring. If I did it was probably silicone lub. The other option is maybe it was leaking at the heater hose connection, but I don't think so.

I am thinking of replacing the heater hose nipple and sealing the o-ring well. Recommendations on what sealer to use?

[TrunkMonkey]

Is it a new o-ring? Or has it been there a while?
A new one, re-used can get abraded or slight cuts and result in leaks.

They often "set" and become flattened on the outer/mating side where it presses against the timing housing.

If I ever remove the manifold, I always replace the o-ring, since it is cheap insurance than to try and re-use one.

Make sure all the inner surfaces where parts slip in and o-ring contacts are clean and smooth.

You can use silicone grease or coat the o-ring and the end seals and holes with RTV (sparingly) and assemble and finger tighten, then just snug, let them set about 30 minutes and torque everything.

[telriv]

I only use a thin coat of The Right Stuff to help things slide together more easily.
To make a POSITIVE seal I use a .060" inner valve spring shim.
It fits the OD of the manifold perfectly.
You need to cut the the OD of the shim to fit inside the cover all the way down.
You can do this on a drill press & a file.
You will NEVER have a coolant leak in this area again.
I've been doing it this way for MANY years now.

Tom T.

[kcombs]

Thank you Tom and Michael for the quick responses.

Tom, the valve shim you mentioned, its purpose is to raise the o-ring a 1/16th of an inch? I could modify a flat washer to do the same thing? (I don't have any valve shims.)

Thanks again!

Kurt

[telriv]

Kurt,

It goes against the manifold & puts downward pressure on the O-ring to make a more positive seal.
Especially IF the inside of the timing case cover has some corrosion in inside.

Tom T.

[kcombs]

Tom, or use two o-rings?

[telriv]

Krt,

You would be hard pressed to crush two O-rings in there.
I have done it in the past & used wood clamps.
Was still difficult.
Came up with the valve spring shim out of frustration which seems to have worked well for me since.
Maybe go to a machine shop to see if they have or can get one.
I could look to see what I have & cut one down for you.

Tom T.