View Full Version : Rusty water coming from cylinder head bolts :-( help!

07-19-2004, 07:26 PM
I have a 1996 20WA with the 351 Ford/Indmar, raw water cooled, carbuerated engine. I just replaced the exhaust manifolds, risers, and exhaust hoses successfully and while I was at it, I repainted the starboard side of the engine block where some rusty water had run down. About one week after the work, I noticed some new rust streaks on my newly painted block. Hmm. Looks like they are coming from three, maybe four of the cylinder head bolts on the starboard side, the ones outside of the valve cover Nothing on the port side.

My guess is that I have a cylinder head gasket leak, allowing cooling water that is flowing throught the head to bleed past the gasket to the bolt holes. I'm thinking of pulling the bolts, cleaning the holes out, and installing new bolts with high-temp RTV. Good idea? Bad idea?

Any comments or experiences will be appreciated. It's a lot of labor to pull the head! :-(

07-20-2004, 09:04 AM
Fly by night
You failed to mention why you changed your exhaust/risers. Was it precautionary or were they leaking? This would be helpful to diagnose your problem. Was the water problem before or after the addition of the new manifolds? Anyway before I would do anything, I would pull the spark plugs, one at a time and visually inspect them to see if they are being steam cleaned. Then I would check the cylinder port and valve for rust with a flashlight. You can compare 1,2,3,4, to 5,6,7,8, cylinders to determine if they are similar. Keep in mind with a raw water cooling system there is relatively no water pressure building up in your engine so a leak usually indicates a bad gasket , or possibly broken part. I would next check the exhaust manifolds you put on to make sure water is not running back into you exhaust chamber of your head. Maybe you have a bad gasket on your riser or it's not tight enough. I would never put gasket sealer on the head bolts. Instead I would remove the valve cover and retorque the head. If this doesnt work I would remove the head and check for cracks that may have occured if you overheated and if none put on a new head gasket. Otherwise you are looking for trouble. Good luck.

07-20-2004, 09:13 AM
I had a similar problem with my 351, also starboard side. The problem turned out to be a small hole in the water jacket on the head. I tried to have it welded but that didn't work, the head warped. I had to replace the head. I only replced the starboard side but everything seems to be working fine . I have put about 150 hrs on it and so far so good. I hope you don't have the same problem but make sure you don't have any rust spots on the head because that's all I saw until I started poking at it. As for putting sealant in the head bolts, I doubt if that will work. If the head gasket is leaking your going to have to replace it.


07-20-2004, 08:34 PM
Seltzer II - thanks for the quick reply. I replaced the manifolds and risers because they had 6 seasons on them and the joints between the manifolds and risers were leaking, especially on the starboard side. Now I suspect that part of what I was seeing as a leak was coming from the three or four head bolts on the starboard side. I will follow your suggestions.

Rejoice - sounds like a thin spot in your head's casting. Tough break. I think I will try Seltzer II's suggestions to see if that helps, and if not, you are right it looks like I'm headed for a head gasket replacement at the very least.

It is strange that there are bolts leaking on starboard but not port.

Thanks for your help.

07-21-2004, 01:31 PM
If you need a set of heads, let me know. I've got a set of 351 heads from a mid eighties 351 that was FWC that I won't be using. I'd give them a valve job before installing, but they were in fine operating order when removed. Let me know if you need, I'm near Atlantic City.

They are not GT40 heads, FYI.

07-24-2004, 09:48 PM
Does anybody know if the cylinder head bolt holes that are exterior to the valve covers are open to the cooling water passage inside the head?

07-28-2004, 08:33 PM
If the bolts that are exterior to the valve covers are not "blind" (in other words in their own hole) I can understand why they could leak. I've been told by a boat mechanic whose opinion I trust that the shop manual for some marine engines call for a sealer on the heads of the bolts.

08-09-2004, 06:58 PM
Ok, I talked to Larry at Indmar and he said I have a 351 "Windsor" block, made in Ontario, Canada. He told me the cylinder head bolts that are exterior to the valve cover are drilled & tapped right into the water jacket. They must have a sealer put onto the threads before installing them or they will leak. He did not know exactly what is recommended as they were sealed by Ford at the factory before they received the base engine.

Does anybody have a suggestion as to what would be the proper sealer to use?

06-01-2005, 07:05 PM
Okay, last weekend, I decided to start tearing the starboard side down until I found out what the problem was. I ended up with three problems going on with the cylinder head:

1. the freeze plug on the forward end under the alternator mounting bracket was leaking,
2. there was a leak in the head casting near the #3 plug , and
3. there is a leak between the exhaust passages and the cooling water passages as evidenced by a large quantity of carbon in the cooling passages.
I started noticing black stuff on the ends of the manifold drain plugs a couple of years ago. I guess that was a symptom I didn't pay enough attention to. Some of the cooling water passages were completely blocked with carbon so I feel certain that the starboard head was running hot. Maybe this caused the two exterior water leaks (?).

I don't believe the water was actually coming from the bolts as the holes and threads were clean. Incidentally, the holes for the bolts exterior to the valve covers did not go into the water jacket.

So I'm getting a rebuilt head for the starboard side, I'm not planning on replacing the port head. Comments are appreciated. The engine has only 260 hours and there is absolutely no sign of trouble on the port side. I figure leave well enough alone. If it ain't broke, don't fix it.

All comments on this situation will be appreciated. Hope others will learn some things to check from my experience. By the way, I love this board and get a lot from it by lurking in the background! :-)

06-02-2005, 09:15 AM
Like I said earlier, I replaced the starboard head only also, now I't been two seasons and everything is still working fine. This spring I replace the manifolds and ells because I could never stop the leaking problem I had with that joint. I have used the boat about 10 hours so far and no leads yet, I hope I have fixed the problem. BTW, I repiped the water to the manifolds, now the water doesn't go through the manifold / elbow joint. I put a closed gasket in there, the type you would use if you had a full FWC system. Then I ran the hoses from the thermostat to the rear of the manifolds, then the water comes out the front of the manifolds and into the elbows through the front tapping on them. Seems to work fine and it keeps the water out of that joint. Hopefully this will solve the problem forever...


06-02-2005, 09:29 AM
Do both heads. You've practically got the job done anyway. You'll really regret it if that other head (or its gasket) gives you problems a year from now. You'd be lucky enough to get to do this job all over again.

One thing I've learned over the years is that a boat is NOT the place to take shortcuts and save a couple of bucks.

Just my 2 cents.