Yanmar 2GM - water in oil - help!

[Cheechako]

How many hours on the engine? Might be good to get the valve seals up to snuff if the engine has a bunch of hours... heck it's off now, rebuild it.... did it smoke when you first started up?

[dr_c]

So I've gotten word back from the machine shop - the head checks out; no cracks observed even under heated magnafluxing. They do recommend a full rebuild and grind, so that's what we're doing. Of course, now I'm gone for a week, but hopefully stuff starts going back together, soon. . .

[HappyMdRSailor]

Originally Posted by dr_c

So I've gotten word back from the machine shop - the head checks out; no cracks observed even under heated magnafluxing. They do recommend a full rebuild and grind, so that's what we're doing. Of course, now I'm gone for a week, but hopefully stuff starts going back together, soon. . .

I've left the machine shop a thousand times... But I have never heard them say "It doesn't REALLY need a rebuild, we'll just clean it up" So... Sounds about right!

Anyway... Glad there wasn't a problem... Make sure they surface the deck so we can eliminate that...

Get yourself a straight edge longer than the length of the block and lay the edge down on it in many orientations... You can use a feeler gauge or strong flashlight to look for low spots or "valleys" on the block mating surface... Do both long sides, corner to corner across, and side to side on each side of every piston....

Let's make sure those surfaces are perfectly flat before we slap that head back on!

Enjoy your week away from your moonlight marine mechanic job!

[dr_c]

(In the meanwhile, the MG got jealous and the water pump now sounds like a coffee grinder. . . And July is coming!)

[HappyMdRSailor]

Originally Posted by dr_c

(In the meanwhile, the MG got jealous and the water pump now sounds like a coffee grinder. . . And July is coming!)

Oh dear... We all know that the cooling system on these babies must be in top notch condition in anything above the 50 degree dreary foggy foggy weather they were designed to operate in! (former TR3A/4/8 owner)

[dr_c]

Happy summer, everyone. Well, I've been sailing and motorsailing and otherwise enjoying the summer. I thought I should finally post a requiem to this thread. Let's review.

Turns out what I needed was a head gasket. On a Yanmar 2GM, a blown head gasket can be responsible for water in oil and low oil pressure after hydrolocking. Case closed.

I did replace the head bolts (in case they stretched during hydrolock), but ended up reusing the exhaust pipe, simply because no-one had one locally. So if you're reading this - keep it simple. A blown head gasket can cause low oil pressure - my original question. And a head gasket doesn't always look too blown (mine didn't).

Fair winds,

Dr. C.