head bolt leaking

[MikeB.330]

I've been noticing a little bit of rust forming around the center rear head bolt along with a some corrosion on the freeze plug.. It looks to me like the freeze plug is fine and that the stud is weeping a little bit of coolant. Would it be better to remove the stud and seal the treads or should I just remove the nut and seal under that.

The engine is MMI unit with fresh water cooling and about 600 hours on her.

Take a look at the pic and give my your thoughts..

Mike

[rigspelt]

This may help:
http://www.moyermarine.com/forums/showthread.php?t=195

[ArtJ]

I am surprised to find such a issue on a Moyer rebuilt engine.
I hope that all studs would have been fixed at rebuild time.

[rigspelt]

I see a ground wire attached to the head stud next to the one in question. When we got our new-old boat there were black ground wires attached to the block in several places. One was attached to the one of two side plate bolts that broke when I removed the old side plate. The other bolt one that broke was right beside it. When I rewired, I put only one ground cable on the engine (the main engine start battery ground), and ran a cable from the engine start battery negative post to a main ground bus to accept all the other grounds. I suppose it is possible that ground wire connections can contribute to corrosion where they attach to an engine bolt, if only from differences in metals, and especially in salt air. I doubt that would have contributed to the rust in this case, but something to ponder.

[Don Moyer]

Mike,

The middle stud on the transmission end of the engine is the one stud that does not normally enter the water jacket, so unless you can actually catch a droplet of coolant showing up on top of the nut or around the base of the nut I wouldn't be too quick to remove the nut for resealing.

My first thought was that the freeze plug may have seeped a bit in which case you could clean the corrosion away and apply a coat of clear epoxy using one of the small fiberglass repair kits from West Marine.

However, I'm surprised by the rust on the head and the corrosion on the freeze plug. A solution of 50/50 antifreeze is usually friendlier to metal surfaces than these indications would indicate. I'm wondering if a bit of water may have dripped down from somewhere above the engine.

Don

[MikeB.330]

Don,

The engine has had nothing but 50/50 since day one. Other than the bit of rust pushing up the paint and the little bit of corrosion on the freeze plug, I've seen no signs of a leak. I've never seen anything leaking out but I know it must be because I'm pretty sure I can see a trail on the end of the head (below the center bolt). It's hard to tell for sure without removing the distributor for a clean view.

I also have thought about water dripping on the head but I can't imagine how it would get there. On the other hand I've never ever even smelled the slightest hint of hot coolant..

In a couple of weeks I'll be doing the end of the season oil change and MMI treatment. I'll have the engine cover off while I get the engine good and hot for the oil change. If it is a coolant leak I'll be sure to see it then..

I've been watching it all year. This spring it there was only the slightest indication of green on the freeze plug.


other replies:
Rigsy,

The ground wire shown is only a ground for the original fuse panel .The only reason it's there at all is because it was part of the OEM harness for that panel.It is on the list of things to change. All of the other grounds come off of a buss bar.

Art:
The engine has been nothing but 110% rock solid and I don't baby her either. Zero complaints whatsoever (that should be a word lol )

[MikeB.330]

Has anyone found a good matching paint that is NOT in a rattle can? A few dabs with a brush is all I'll need and with times what they are $18 for spray can of paint is a bit steep.

[Don Moyer]

Sounds like a good plan Mike.

If it turns out that coolant is appearing on top or from under the head nut you can remove the nut and pour some Permatex Aviation Brand sealer between the head and the stud allowing it to cure well. Since you'll be out of the water by that time you could allow the Permatex to cure several days.

If the freeze plug is seeping, you can follow the guidance in the attachment.

Don