4.6L Intake Manifold Question

Now that I have finally solved my cranking issue, I need to move on to my next repair project.

It starts with this question:

Does the 4.6L stock intake manifold have any coolant passages in it OTHER than where the heater hoses are attached? If so, where are they located?

For the record, I replaced my intake manifold with a re-designed stock replacement a few years back. This question does not concern the typical heater hose leak...

A few years ago, my 1996 GT intake manifold developed the common coolant leak.

I replaced the intake manifold with a new, re-designed aftermarket unit. It had an aluminum coolant crossover. The intake manifold worked fine for quite a while after that.

Now, my intake manifold has developed pretty severe coolant leaks in at least two places--just beneath the thermostat housing, and also near my #8 cylinder.

I recall that my aftermarket intake manifold had built-in O-rings.

I am almost too embarassed to ask this, but here goes:

Was I supposed to use intake manifold gaskets? I thought the O-rings made gaskets unneccesary. Heck, I didn't even think gaskets for this intake existed! And the manifold has worked fine up to now.

I am about to swap the intake manifold yet again...but it got me to thinking. Fel-Pro does make a gasket set for the 4.6L V8. Do I need to buy this gasket set, even though the manifold has built-in O-rings?

I feel like such a dummy, but my car'sView attachment 137163 original intake didn't use a gasket set!

I am more than happy to buy the gasket set if I need it...but one thing is for sure: If I DO NOT need the gasket set, I sure do plan on using plenty of Permatex around the coolant passages! I'm tired of these coolant leaks!

bdcardinal:

I wonder if I should go ahead and get another replacement intake manifold, take out the O-rings on it, and use the flat gasket set, with plenty of Permatex. I just don't know if the O-rings by themselves are sealant enough.