Miker
Well-Known Member
Last sail of year today. No wind so hammered engine for 7 miles. Not a sign of a leak! Will winterise then see how it goes next year.
Replacing sump gasket
- Thread starter Miker
- Start date
vyv_cox
Well-Known Member
An intermittent leak like yours can be very difficult to solve. Did the leak occur when the boat was heeled, i.e. motor sailing. This could indicate that it is in fact the sump. If not then it seems more likely to be one of the oil seals. Since these usually either leak or don't leak, it may be that the crankcase is pressurising sometimes. Check the pressure relief valve system and clean it up. Don't know about your engine but this happens on Bukhs when the suction tube from the valve into the air inlet blocks with carbon.
Miker
Well-Known Member
The oil leak occurred when not heeled. I will be replacing the oil filter so could have a look at the reducing valve. Found the pressure reducing valve in the workshop manual. Presumably I would need a replacement seal if I take it out to clean. Also I do not know what torque required for reassembly. The manual gives 60-70 for the relief valve and 35-39 for the pressure valve holder.
vyv_cox
Well-Known Member
No, not the oil pressure relief valve. There will be a breather arrangement on your engine, whereby suction from the inlet manifold draws fumes from the crankcase. There is usually a simple spring-loaded valve that opens when the crankcase pressure exceeds a certain (low) value, drawing the fumes into the manifold, then closing again. If this doesn't work for some reason, usually carbon accumulation, the crankcase can pressurise and oil will be blown out of the seals.
VicS
Well-Known Member
I cannot find any parts for a crankcase breathing system on the parts lists although there is a "separator" and a "filter" in the rocker cover. That must be it I think.
Slacken the oil filler cap carefully to see if there is any pressure under it. If there is much then investigate the filter and separator.
All the workshop manual says is,
"Crankcase ventilation
To prevent overpressure and to separate fuel vapour,
steam and other gaseous combustion products, the engine
is fitted with enclosed crankcase ventilation."
To prevent overpressure and to separate fuel vapour,
steam and other gaseous combustion products, the engine
is fitted with enclosed crankcase ventilation."
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Miker
Well-Known Member
I will leave the relief valve thingy well alone. Thw workshop manual mentions crankshaft ventilation but gives no details.
VicS
Well-Known Member
See the edit to my previous post
vyv_cox
Well-Known Member
It sounds like it may be similar to the Bukh one. On the 20 there is a small drilling (about 5 mm) through the head, finishing inside the air passage on one of the cylinders. This connects to the crankcase for the purpose of drawing fumes out. There is no mention of it in the workshop manual and the drilling is not shown on any of the drawings I have seen. Over time this drilling blocks with carbon deposits with the result that the crankcase over-pressures.
VicS
Well-Known Member
I was wondering what parts 32 and 33, described as "separator" and "filter", were. At first I thought they would connect with a hose but #35 is just a plug not a hose nipple
vyv_cox
Well-Known Member
I was wondering what parts 32 and 33, described as "separator" and "filter", were. At first I thought they would connect with a hose but #35 is just a plug not a hose nipple
They look like very similar parts on the BMC A-series, but as you suggest, on that engine the part #35 is a nipple that connected via hose with the air filter on the gasoline engine.
Miker
Well-Known Member
I'm afraid this is out of my depth. I will have a word with the chap who services my engine when it goes back into the water next year. Thanks for all your advice.