Water Outlet

[lyle11]

I just started my 55 Lowboy for the first time after I replaced the rear main seal (from Tim) in addition to rewiring to add lights. All good with one exception. One issue that I also worked on was a slight seepage of coolant where the water outlet bolts to the head. It was slight, but enough to collect around the #1 plug and corrode the base of the plug.

I removed the water outlet and found that rubberized sealant was used instead of a gasket. So I got a new gasket from TM, thoroughly cleaned the mating surfaces and used Indian Head gasket shellac. Reassembled it a couple of weeks ago and after first running it for 30 minutes today, it seeps coolant far worse than before. Tightening the bolts more after the engine warmed up didn’t stop the leak. So it looks like rather than just not having a gasket the PO used excessive sealant to fix this issue.

After it cools I’ll take it apart and examine the outlet. I think I did everything right so my question is:

Do some of these water outlets have less surface contact just due to variations in the casting?

I’m reluctant to put it back together because, short of using a lot of gasket sealant, which I hate to do, I don’t think I’ll get a different result.

The picture below shows where it leaks on the generator side. There is extra 1/8” or so of mating surface on the head that the outlet doesn’t cover. Once I get it apart again I can look at the casting surface closely. Hoping a different water outlet with more mating surface area will fix it.

Thanks

C7C26AEA-A48E-4567-8F18-6E2CF99198DD.jpeg (61.28 KiB) Viewed 342 times

[Urbish]

Hold a small 6" metal ruler or other known flat item long enough to span the mating area to the flange on the coolant neck as well as the head. Check all areas and in all directions. If not flat, you can carefully dress the high spots with a file. Inspect the head area to ensure that you don't have a crack that is hidden when the two are bolted together.

[Crimson Tim]

You are probably on the right track since you changed the water outlet seal and it changed the amount of leakage, but I’ll just throw this out there, too: remember that the head bolts pass through the water jacket. If sealant was not used on them or that sealant has failed, you can get coolant seeping up around the head bolts and end up there.

[lyle11]

Thanks for the replies. I removed the water outlet and couldn’t see much with a straightedge. Then I pressed it onto a flat metal surface and it rocks back and forth and there is a visible gap where the seepage occurs that looks at least as wide as the gasket is thick. It’s obvious it isn’t gonna fit snug without significant filing. Rather than try to file it flat. I have a spare I removed from another Cub at my other place and I’ll see if that one is flat.

[john2189]

A belt sander should flatten it, if you have one

[ntrenn]

Sandpaper on a glass plate works too...