Lister SRM oil leak in way of cooling air.

[nickcirrus]

Hi there It's me the one with the Lister SRM3 which I have in my sail boat and I was sold the wrong sized pistons last year. 
The latest update is the engine is working well though I have had some overheating due to the louvres in the cooling air outlet of the engine box. I have since removed them and so far the engine has not overheated again.  However I have some oil spatter coming out with the cooling air, ( makes a bit of a mess on the Teak flooring). Thought at first it was coming down the head fixing studs that also hold down the rockers, so I resealed the thin gasket beneath each rocker assembly. Thought the leak was solved but no such luck!  Am running out of ideas. There seems to be small drops of oil collecting on the top of the cooling fins and this is being picked up as the cooling air exits. Could I have got the gasket and shims the wrong way round? Though I can not see how oil could come out of the top of the cylinders. Could I have a cracked cylinder/cylinders or head/heads. Has anyone out there experienced this problem and worked out why.

[mike90045]

Is it thin engine oil, or possibly exhaust combustion slobber ? (inky black)

[nickcirrus]

I would say it is just engine oil. hard to say anything else. of course it is thin because it only happens once the engine has warmed up some. I guess it could be the D rings but having shone a torch in there the oil collects on the uppermost cooling fins and not behind the aluminium pushrod housing, and in any case I replaced the D rings.

[millman56]

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    Did the oil leak occur after the overheating event ?   Overheating may lead to piston,rings and bore damage with the likleyhood of increased crankcase pressure,   couple this with some settling and hardening of gaskets and leaks may occur. 

It might be worthwhile removing the starter motor and looking for oil on the inside of the volute and on the flywheel,    this may indicate a leak from the main bearing housing or a faulty crankcshaft oil seal, any leaks here are picked up and spread throughout the path of the cooling air.

Hopefully it will be something simple,    good luck!!! 

Mark.

 

[Combustor]

Hello nickcirrus,
                       Agree with Millman56 that it is coming through with the cooling air. Do you know what type of crank seal your SR has? Think there was a brass spiral ring and a felt washer on some,
 and they can leak a bit. Should be a tube under the rocker cover(s) connecting int the intake port to keep a slight vacuum in the crankcase and draw oil in. Check the tube(s) are clear.
         The brass ring and felt can be replaced with a normal double lip oil seal, but means pulling that flywheel!   Also recall a drama with an ST (similar engine) where there was a plug with an O-ring
behind the flywheel blanking an oilway at the end of the camshaft. The finer detail escapes me now, but if you should have to pull the flywheel, check this location for possible leaks.
         Hope it turns out to be something simple.  Combustor.

[nickcirrus]

Many thanks for the replies guys.
I just got back from some sailing out and about.

Hmm, removing the flywheel is about the last thing I am keen to do. It is also the only thing I have not done. Thinking about it it does seem possible that the crank seal could be at fault. Not long after getting her running I stupidly forgot to check the oil level and the next time I fired her up a whole lot of oil came out with the cooling air. Yes I had fuel leaking out of the return pipes and it had filled up the sump right up to the filler cap!!! had to mop out the oil mix in the fan housing and then degrease all. I replaced the leak off piping. Can't see any oil in the fan housing now though but that crank seal is a likely culprit, though I would have thought that the cylinders would be more covered in oil than they are. It appears to be only at the top of the cylinders!
I did wonder If it could be the oil seals in the exhaust valve guides. The amount that comes out is only a few spatters and only every ten minutes or so but does increase as the engine heats up.

May be Im clutching at straws but the idea of pulling the flywheel and fan etc means lifting up the engine and all that that entails in a boat. 

Engines are great when you need em, but the wind is free and cleaner!