emulsafied oil in yanmar

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john m

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i think my engine has been damaged by frost (no antifreez when bought) i have teken the cylinder head off and cant see any damage what next i am hoping to repair this my self on the basis that if i strip the engine i should be able to rebuild it but how do i fins the problem .
the engine was runing ok thanks in advance
 
a few more clues as to

the engine - which one?

why do you think it was damaged? if sump oil emulsified was there a drop in cooling water level or not?

also confused as to the question you are actually asking?
 
I suggest you change the oil, and run the engine, if there is a water leak the new oil will emulsify and you are in for a strip down. It is just possible that the oil in there now was contaminated, and that you do not have a leak caused by a freeze. One thing to check. Is the oil in the sump clean, and the emulsion only in the rocker box at the top of the engine? I had a petrol engine in a van once, that was always like that, but never gave any trouble and I never did find any leak.
 
Re: emulsified oil in yanmar

Obviously you have water in the oil for it to emulsify and this has happened with the engine running as if it wasn't running at all, the water wouldn't mix with the oil. The most common cause would be the head gasket (I don't know the intimate details of your engine but few modern engines have integral heads (I don't know any but that doesn't mean there are none out there).

The other probable cause might be a cracked cylinder barrel or head. With a cracked head there'd most likely be overheating in the engine and the alarm would sound, due to combustion gases finding their way into the coolant rather than vice versa.

I'd expect the engine to have a pop-out core plug to protect against frost damage. These are usually metal dishes which are hammered into a hole cast in the block. If you ran the engine up with the core plug out, the cooling water would just flood into the bilge.

If the emulsion is only in the rocker cover and the sump oil is OK, it's likely to be due to a blocked crankcase breather (Brileymoco "A" series engines - mminor, A35/40, minis et al were similarly effected but in this case the rocker box breather was also a probable cause).

Hope this helps
 
You really havent given enough info. Which model Yanmar? Is it fresh or raw water cooled? Is it new or second hand? Is it installed anywhere where water could get in through fillers/ disptick ettc. What makes you think there is water in the oil? In what circumstances?

If it is one of the smaller raw water cooled engines (1GM, 2GM etc), then the oil feed to the head is external and the cooling water isnt under much pressure so the problem wont be a head gasket unless there is distortion through overheating. You would be able to see by looking at the gasket removed. Corrosion in the exhaust area could be a problem if salt water has splashed back into the head through failure of part of the exhaust manifold. Then water gets into the oil return flow from the head. Dont ask how I know!

If it is a fresh water cooled engine, and assuming there are no cracks evident in the bores (should be lines of rust) then the best thing is to put the head back on with a new gasket and get the cooling system pressure tested.

But from the info you have given there could be lots of possibilities, so if you want more suggestions you need to post more info.
 
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