Problems

[Easternsun]

Question . have a yanmar 3agm 30 f . when I open fresh water filler cap , you can see exhaust smoke coming out . its also depositing soot into the fresh water which is turning into sludge , which is getting on the heat exchanger and causing motor to run hot . Also because its coating the thermostat with sludge its preventing that from operating properly . The obvious thought " I think "? Is that there's a crack in the exhaust manifold between exhaust and fresh water reservoir. Inspected it thoroughly .no sign of crack . Any ideas . ?????? Signed : stranded at the moment in the Abicos . help !!!!

[Wotname]

Easternsun, welcome aboard CF.
Can you see any bubbles in the fresh water tank - if so, you may have blown head gasket.
Hopefully some of the more diesel experts will chime in soon with other (better?) ideas for you to explore.

[GordMay]

Greetings and welcome aboard the CF, Easternsun.

[Sailmonkey]

You’ve got either a blown head gasket, or a cracked manifold.

More likely the wad gasket though. A cracked manifold would allow coolant to leak out too.

[sailah]

You describe very similar symptoms to my head gasket issue. I was getting exhaust in coolant bubbles clearly visible. Would push all coolant out if motoring looking enough and overheat. This was on a westerbeke.

I finally removed head and checked it on a surface plate. Was warped so i had a machine shop surface it flat again. All is well.

They sell a combustion gas analyzer that looks like a Turkey baster. You put it where radiator cap is and run the engine for 30 seconds. If it fails you likely have a bad head gasket but do check the head for flatness if you remove because gaskets don't just fail on their own typically.

[Easternsun]

I am observing bubbling in the coolent and there is a slight loss of water over a period of several hours .

[Wotname]

Then likely culprit is a blown head gasket.

[sailah]

Sure feels like a head gasket to me as well. Here's my thread on this very subject. Different engines but same symptoms.

http://www.cruisersforum.com/forums/...4b-203739.html

I had removed the head 3 years prior to this due to a bad valve and so had put on a new head gasket at that time. Seemed implausible that it would go bad so soon. I tried throwing parts like thermostats and radiator caps at it hoping it was maybe a simple overheat issue.

In the end it's not that big of a deal and really not that expensive assuming you would do the heavy lifting. The combustion gas analyzer is the best way to check but since you already have exhaust gases coming out of manifold you can save yourself the $60 and just assume you have a bad HG.

Your comments about sludge getting on HX and overheat aren't the same experience as mine. My engine would also run hot and here's what I found. I had a leak between cylinder 2&3 on my Westerbeke. The compression of the engine is 450psi. Which is enough to force combustion gases past the HG and into exhaust manifold. Once there, and given time, it would force the coolant out past the radiator cap and up to the expansion tank. Once enough coolant has been forced up to expansion tank, there wasn't enough to circulate around engine and the temp would rise.

What made it even worse was slowing the engine down. Every time I would have an overheat alarm it was when I throttled down, presumably from lack of circulating power at lower rpms.

Anyways I think the fix for you is to find a good machine shop that can inspect the head. They do this either with a precision straight edge and feeler gauges or with a surface plate and Dykem. I have both here in my home machine shop so I checked it myself and also had machine shop check it. If you look at my thread I posted a pic of the Dykem (ink) and the blue spots were where the head was low. I also had the machine shop magnaflux the head which is a way to use special powder and an electromagnet to check for cracks in the head. That came up negative and the machinist said it wasn't necessary but I wanted it done belt and suspenders.

So other than my time, and I had all the tools like a torque wrench, it was $75 for a new head gasket, $90? for the head to be machined with CBN tooling, $180 for magnaflux (skip this) and some odds and ends.

I think hardest part of the job was preparing the engine gasket surface and removing all old gasket with a razor blade and not getting crap down into engine. I used a variety of expandable rubber plugs, shaving cream, tape etc to keep it as clean as possible.

[Compass790]

Yes I'm with other posters, likely blown head gasket.
The tip I have for you is if you cant get head machined there & you are worried about it's flatness when installing the head gasket use Loctite 518 flange sealant. Don't be frightened about the word loctite, you can can still get the head off easily after using it. I have even used it to re-install used diesel head gaskets with no issues.
It fills up imperfections up to 0.05mm easily. Guess you'll have trouble finding it there but if you getn head gasket flown in get that too. Permatex makes an equivalent as well.
good luck with repair

[Easternsun]

Update: . Took the suggestion that it was a a head gasket problem . Had the head machined ,new gasket and mechanic put it back together . Now engine won't start . He did a compression check on one cylinder . 160 ,it's suppose to be around 400 and something . What on Earth would be causing this ?. HELP PLEASE !

[Compass790]

Remove rocker cover & check that all valves are operating properly for a start
I'm not sure but I think some of those models are prone to cracking pistons/ring lands.
From my admittedly poor memory Sailorchick & Cheechako know about those issues, you could pm them.
There may be another reason, just two possibilities that spring to mind

[Compass790]

check this out from google custom search:
http://www.cruisersforum.com/forums/...ne-149736.html

[CassidyNZ]

It would seem unlikely that any engineering company would machine a head and not notice cracks. But then again, one wouldn’t expect a mechanic to refit a head and not check his own valve clearance settings when confronted with one pot down on compression.

Check your valve clearances, a tight tappet will cause the loss of compression and it’s a simple place to start.