Leak on top of SBC 350 intake manifold

When check my SBC 350 after driving home from work I find a small pool of antifreeze on the intake manifold near the water neck. It looks like the leak is either from a bad seal between the water neck and the manifold, or from the bottom side of the upper hose where it fits over the water neck.

The manifold is an Edelbrock Performer EPS, and I've tried both the original water neck from my '75 iron manifold, and a replacement water neck from the parts store. I used a stock gasket and some red permatex. Radiator hose is not new, but is in good condition and the clamp is tight.

I've had the minor leak for the last couple of years, and I've finally decided that I have try harder to get it fixed. I will again use a new gasket and sealer on the water neck and a new radiator hose, but what else should I check? Could the manifold surface be that uneven where the water neck bolts on, or could water be coming through the manifold casting? I don't want to use any sealer between the hose and the water neck because it will be too hard to replace a hose later on, but is there any other way to improve the seal?

Any other suggestions on what to check and/or what to try to get this sealed?

Thanks,

Bruce


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The only sealants I use for coolant, are Blue Permatex, or Gasgacinch.

I have found Red Silicone does not work with coolant. It is designed to work for high temperatures, such as exhaust manifold gaskets, not oil, or coolant applications.

check for flatness on that surface right there...

I would take it for a drive, giving it time for pressure to build up, then pop the hood and shine a light to find where the source of the coolant is coming from.

New or old style manifold ? have you used a torque wrench so as to make sure you have even pressure, clamping of the neck to the manifold. Having a leak for two years I am betting there are stains you might use to find that leak.

I will say this I have had mystery leaks like you post and found that sometimes running hard will cause things to shift and coolant will burp out in this area.. got it stopped after I did the torque set and check manifold dance. might be seen as over kill by some but I go with what works. A torque wrench is the last tool I use after assembly of most parts ..... separates the shade-tree mechanics from the real ones ..

Thanks for all the suggestions. I've already thought of most of them, but this time I'm going to be more methodical in my approach.

The problem with this leak is that its very slow, and doesn't show up with the engine idling. Its definitely toward the driver's side of the water neck, but its very hard to tell if its from the gasket area or coming from the edge of the hose. Remember, this area is right behind the fan, and when you are driving at highway speed (which seems to be when it happens) the anti-freeze doesn't drip down in a nice steady stream. A little bit of everything seems to get wet.

I am going to pull off the water neck and upper hose, and verify that the manifold is completely flat where the housing bolts on. I will then reinstall the water neck, sealing it with Permatex Water Pump and Thermostat Housing RTV silicone, and torque the bolts to the right torque (I have to check to see what that is). I will then install a new radiator hose, using standard worm clamps.

Question - If I use the Permatex Water Pump and Thermostat Housing RTV silicone, should I also use a standard gasket. The directions seem to indicate that it is used instead of a gasket.

Thanks,

Bruce

Use just a small film of silicone, on both sides of a new gasket.

or steel or some off breed pot metal ? if so they expand different at different temps just enough to warp and seep try a honest to goodness alluminum water neck - bet leak stops -

This shouldnt be hard to fix. Drain your anti-freeze just a bit and pull off the hose, inspect the hose real good or replace it. Remove the housing, scrape off EVERY BIT OF GASKET ON BOTH SIDES and make sure that the part that the hose goes onto is good and clean and smooth. Inspect the manifold and inlet housing for cracks. Reinstall with new gasket and just a tad of silicone sealer if you wish. For extra insurance you can reinstall the hose with a little bit of super wetherstrip adhesive and double clamps. If you use the gorilla snot then make sure the inside of the end of the hose is clean and dry and then just put a bit on the housing. Fill it back up and take your wife out to dinner..

Are you 100% sure it's the water neck? I have seen leaky intake manifold gaskets where the coolant spurted up a little and pooled on the manifold, it looked like it had come out of the hose or neck but wasn't. Always use sealant on the coolant ports at the ends of the intake gasket.