F20 coolant leak

doehmke · Oct 1, 2013

Fired up one of my F20s after totally redoing the engine, to include having the head gone through and all new valves and surfaces ground, magnafluxed, etc. Also, the shop repaired a crack by one of the valves. Engine runs very nicely, but I watch coolant seeping out from under the manifold gasket's bottom edge, just to the left of the 2nd manifold stud from the front of the engine. It is very slow in forming individual drops, which drop one at a time down side of the block.

Don't have any coolant getting into either the crankcase the crankcase or manifold and carb from what I can tell.

Any thoughts on if this might be a manifold stud turned in too far and coolant from the water jacket is seeping out the bolt hole? Would high temp sealant on the stud threads possibly take care of this? Any other ideas short of pulling the head and having it rechecked or replaced?

36F30 · Oct 1, 2013

The holes for the manifold studs actually go clear through the head and need to be sealed with sealant during assembly. You will have to drain the coolant, remove the carb and manifold and then the stud. I use aviation form a gasket but any thread sealant should do. Coat the stud and put it back in. Might as well do them all while your at it. let it set up overnight and reinstall everything. The bolts holding the oil pan on also penetrate the block and will leak oil if not sealed and will mess up a nice paint job. Bottom line is the F series likes to mark their territory.

Tom Fleming · Oct 2, 2013

36F30 is spot on. When working on these, keep a tube of Permatex forma gasket on hand. Works great, and you don't need a whole lot. just put a dab on the threads, run your finger around them to level it out, and install. simple. works.

doehmke · Oct 2, 2013

Thanks, 36F30!

doehmke · Oct 2, 2013

That's good to know, Tom. Didn't see any oil leaks yet on the pan, but sppose it wouln't be long if ghat's the case with the bolt holes. Only had it running 3 times so far about 10 minutes each on a temporary gas tatank. Though that was enough time for one of the inpection covers to already leaking oil, despite new gaskets. Suppose the cover may be bent and not sealing properly.

doehmke · Oct 2, 2013

That's good to know, Tom. Didn't see any oil leaks yet on the pan, but sppose it wouln't be long if ghat's the case with the bolt holes. Only had it running 3 times so far about 10 minutes each on a temporary gas tatank. Though that was enough time for one of the inpection covers to already leaking oil, despite new gaskets. Suppose the cover may be bent and not sealing properly.

Tom Fleming · Oct 2, 2013

Not a problem. The F-series does not seal everything up tight like 36F30 says. They will seep a little around seals and that is a fact of life. However, the head bolts, manifold bolts, oil pan bolts, some of the transmission bolt are open to the fluid chambers (oil pan, cooling jacket, transmission, etc.) these bolts/studs all should get a dab of your sealant of choice. I like permatex, however, use what YOU like and have good experience with. None of these are high pressure, so like the old TV commercial, " a little dab will do ya".

doehmke · Oct 7, 2013

Pulled the manifold studs this weekend, put sealant on the threads, reinstalled, topped off radiator the next day and ran it for about 10 minutes with the temp gas tank. Not sure how long you need to let the sealant set, but didn't fill with water until the next day. Anyhow, the drip has been resolved. Thanks, guys for pointing me in the right direction.

F20 coolant leak

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