Been rebuilding my truck, and today, while replacing a noisy tensioner, I found that my valve cover vent tube was dripping a clear water looking substance. I smelled the liquid, and it seemed to be very clean and clear Gasoline, maybe slightly diluted. If i hold the open tube up to the air intake, it has enough gas vapor in it to increase the engine rpm's slightly. I'm sure this has been happening for awhile, but I really did not notice it untill today. I am under the assumption that i may have some leaking valve seals. I really dont think its rings, becasue the engine checks out under compression test. All cylinders are exactly the same! So, it must be valve seals right? Another possible indicator of valve seals, is that I have a few plugs that foul pretty easily.

So, my question is, what is involved in replacing the seals. I cannot find any real description of the procedure on the net, and i am to lazy to look in my workshop manual. Has anybody here changed them, and can it be done without removing or replacing the valve guides.

Also can you get the parts NAPA or the like seeing as it is a common merc motor.

Oh, and a few weeks ago, i replaced the back side exhaust manifold because the original was cracked on the runner. While the truck ran with the cracked runner, it tended to ooz out oil and gas mix. I played this down becasue the truck was having bad problems with fouling because of bad plugs and a bit rich mixture. But that really did not explain the oil. But valve seals would explain why I saw oil, especially since the cylinder was not firing, thus it did not burn off or force the oil out the exhaust.

So unless someone here know different, I am going to say its vavle seals. So, again whats involved.

Puffdragon:

I use to have a 404 that had alot of problems fouling plugs. It was always the 5th or 6th plug that got fouled. It was worse going at slow speeds when you were rock crawling but worked fine going at speeds on a highway. It was less of a problem at sea level but 7000 ft (Flagstaff Az) it ran like crap. When crawling at idle you are usually going up hill and all the fuel runs to the back (5th-6th cylinders). When at Moab one year I put a set of smaller jets in the carbs and it ran better on the trip back to the west coast.

Things you might consider before the valve seals.
1. Running hotter plugs
2. putting smaller jets in the carb
3. Lowering the float (less fuel will spill over when at angles)

It appears that you do not live at sea level.

I use to have a set of valve seals left over from a rebuild laying around but haven't seen them in a few years. If I can find them you are welcome to them.

Good Luck
dan

Any one need 406 axles: http://www.pirate4x4.com/forum/showthread.php?t=312824&highlight=unimog+axles

I am already running the leanest jets I can. The jets are 120's I am also running a very hot plug. I can make the truck run without major foulinig etc. The truck really does not have major run issues at all, even with a worn out cam and rockers. But the thing that gets me is the amount of fuel building up in the top end.