How heavily should an oil-breather breathe?

Frayed Knot

Frayed Knot

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My Beta 1005, which has run for less than 1000hrs, creates a strong smell of hot oil almost as soon as it starts to warm up, which soon reaches into the cabin. I've checked thoroughly for leaks and have tried lowering the sump level to a little below full on the dipstick with no effect. The oil pressure is constant at about 55 psi whatever the revs.
When I checked the oil breather pipe, which was clean, I could feel a slight flow of air when I held the end close to my face with the engine running at about 2200 rpm & when I held my thumb over the end for about 30 seconds although I couldn't feel any pressure there was a definite "puff" when I released it.
I've no idea if this is normal so any advice would be welcomed -my only guess (& I sure hope it's wrong!) is worn valve-stem guides.
 
Sounds just about normal. A build up of air pressure in the crankcase is caused by blowby past the pistons in the bores and is quite normal even in a new engine. Not normally due to worn valve guides unless the engine is on its last legs and yours certainly is not.
Not knowing the engine in question, but that pipe would normally return any expelled fumes back into the air intake/filter or whatever is fitted so that the engine consumes it again. Fumes would soon fill the cabin if that pipe was not reconnected.
 
+ 1 re SAMI's post.

Also not this return air should go back via the filter as it will clog most types but OK for the metal wire type, many have a connection just below the filter to avoid this clogging probem.

Good luck and fair winds. :)
 
Isn't it supposed to suck, rather than blow? I know nothing about that engine, but every car and motorcycle engine I've ever seen had a crank case ventilation system sucking from the inlet manifold. Positive pressure was an indication of blown piston rings.
 
elton said:
Isn't it supposed to suck, rather than blow? I know nothing about that engine, but every car and motorcycle engine I've ever seen had a crank case ventilation system sucking from the inlet manifold. Positive pressure was an indication of blown piston rings.
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All engines have positive crankcase pressure, some are to atmosphere, others are routed back to the inlet pipework, mainly for emissions i think.
Basically the more it fumes the more worn the motor is, i see plenty of trucks with a million kms and their breathers are like little chuffing steam engines!



Lynall
 
Frayed Knot said:
My Beta 1005, which has run for less than 1000hrs, creates a strong smell of hot oil almost as soon as it starts to warm up, which soon reaches into the cabin.
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In an enclosed environment like a yacht engine compartment, especially with a modern engine I would expect the crankcase breather to be connected to the engine air intake; either to the air filter or directly to the intake manifold, as suggested in previous replies.
I suggest you look carefully for a place from which this pipe has become detached.
 
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VicS said:
In an enclosed environment like a yacht engine compartment, especially with a modern engine I would expect the crankcase breather to be connected to the engine air intake; either to the air filter or directly to the intake manifold, as suggested in previous replies.
I suggest you look carefully for a place from which this pipe has become detached.
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Sounds like the breather pipe has become detached as others have said. If not there's probably an o ring on the dipstick where it enters the block but would be surprised if that has gone given the low hours. You can pop your finger over the breather and blow down the dipstick pipe to check for obvious leaks. Having said this I was checking for 'oil fumes' for months on my beta 20. Turned out to be a combination of a leaking diesel tank and perished leak back pipes which were dripping fuel onto a warm engine - smelled just like hot oil to me :-) Does the engine start on the button or does it take a few moments to get going on all cylinders. The latter is a sure fire sign you have a leak some where.
 
elton said:
Isn't it supposed to suck, rather than blow? I know nothing about that engine, but every car and motorcycle engine I've ever seen had a crank case ventilation system sucking from the inlet manifold. Positive pressure was an indication of blown piston rings.
Click to expand...

Most automotive engines collect the crank case fumes from the rocker cover and return them to the intake manifold via a valve. This type suck air. (remove the hose from the cover and it will blow).

Other engines collect the fumes from the crank case and direct it to the ir intake. This type blow.

Good luck and fair winds. :)
 
lynall said:
All engines have positive crankcase pressure, some are to atmosphere, others are routed back to the inlet pipework, mainly for emissions i think.
Basically the more it fumes the more worn the motor is, i see plenty of trucks with a million kms and their breathers are like little chuffing steam engines!



Lynall
Click to expand...
They aren't supposed to blow crank case fumes out. Negative crank case pressure is maintained to the EGR system. Positive pressure is a sure sign of a malfunction, and probably an MOT failure (on a road vehicle, obviously).
 
Sorry, Elton, that's complete gibberish.

What has the egr - exhaust gas recirculation system (not fitted to boat engines) got to do with crankcase ventilation?
They are two completely different unrelated systems.

There most certainly is positive pressure in the crankcase of any engine - as has been mentioned, from piston blow by and it is usually fed into the inlet manifold - ie after the air filter.

A hot oil smell would suggest some engine wear, but if it doesn't use (or burn) oil and the oil p is good, then nothing to worry about.
 
Have you considered the possibility of the fuel pump diaphragm being perforated, allowing Diesel to enter the sump?

This would allow more 'breathing' than is normal!? an oil change would temporarily stop this....
 
All engines puff a bit, if there's trouble there is not usually any ambiguity about how much should come out of a breather! What you have sounds perfectly normal.

Try running the engine with oil filler cap off nothing much should come out but you will be able to feel air moving if you put your hand over the opening.

As others have said the breather should be connected to something, usually the air cleaner or inlet manifold; diesels have no manifold depression to speak of so they don't scavenge the crankcase in the way petrol engines do. The other end of the pipe is usually connected to the valve chest or the rocker cover.

What you describe is THE other reason for fitting an engine compartment ventilation system the blower extracting the smelly air from the engine compartment, with another air pipe from outside to provide fresh air to the engine which is the main reason for the system..
 
What you have described about the air from the breathing pipe sounds normal. There is ALWAYS positive pressure through the breather pipe, if there is too much air under pressure coming out then there is a problem with piston rings (worn; broken; carbon); but you will know if you have pistons or rings worn out as the air and oil spitting out will be too obvious.

As the other suggested, the air should be recirculated via a pipe; hence look for a dislodged pipe; if missing, you may have to make up a pipe to divert the air back to the engine. However, make sure that the problem is indeed the breather pipe and not something else ie leaking fuel or dripping oil on the exhaust etc
 
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