volvo penta ms gearbox breather

[colvic987]

I have a volvo penta ms gearbox which i repainted last year, i am now having a problem of the oil being sucked or blown into the engine sump, so i presume that i have a blocked breather hole.

does anyone know where the breather hole might be in the gearbox, i have looked but with the repainting its not looking obvious.

 

[pvb]

I'm not sure why it would need a breather hole. Sounds more like a failed oil seal. You can download a manual here.

 

[Bilgediver]

I have a volvo penta ms gearbox which i repainted last year, i am now having a problem of the oil being sucked or blown into the engine sump, so i presume that i have a blocked breather hole.

does anyone know where the breather hole might be in the gearbox, i have looked but with the repainting its not looking obvious.

What makes you think the oil is going to the sump?????
There is a gear box input shaft oil seal....a crankshaft oil seal .....and a big coupling space in between which has a drain hole????

 

[colvic987]

What makes you think the oil is going to the sump?????
There is a gear box input shaft oil seal....a crankshaft oil seal .....and a big coupling space in between which has a drain hole????

Tks for your reply, this one has got me stumped, the reason i think the oil is going into the sump, is that once i have filled the gearbox with oil and the engine dipstick is at its max fill, after a couple of hours use the gearbox oil is down and the engine sump is up. my engine is on an incline down to the gearbox at the lowest level, but the engine sump is being filled, that is why i think that the oil is being sucked or pressurized into the sump....

engine oil presure guage is operating under the usual pressures depending on the revs ....

 

[VicS]

What engine are we talking about?

 

[colvic987]

I'm not sure why it would need a breather hole. Sounds more like a failed oil seal. You can download a manual here.

tks for your reply, and direction to manual, if the failed oil seal was at the higher level of the gearbox would it still leak into the engine sump which would mean it would have to travel upwards along the rotating input shaft...

 

[colvic987]

What engine are we talking about?

md7a with ms gearbox

 

[pvb]

tks for your reply, and direction to manual, if the failed oil seal was at the higher level of the gearbox would it still leak into the engine sump which would mean it would have to travel upwards along the rotating input shaft...

But why would it need a breather hole? What's going to cause pressure inside the gearbox?

 

[cimo]

But why would it need a breather hole? What's going to cause pressure inside the gearbox?

can't say for sure (temperature likely plays a part). My own ZFmarine box does have a pressure characteristic. Has a breather valve at the top towards the rear of the casing. Unfortunately, can't see anything similar in the linked manual though.

 

[earlybird]

FWIIW, my Hurth box breathes via the tubular dip-stick. A very small hole, ~1mm dia. drilled into one of the hexagon flats, connects with the tube. Difficult to spot if blocked with gunge, which easily happens.
The Volvo box seems to have a similar dip-stick, so might, perhaps use this arrangement.

 

[colvic987]

But why would it need a breather hole? What's going to cause pressure inside the gearbox?

This is the problem which i cannot solve or have any idea of, but the obvious clue is that i have changed in characteristics is that i have painted the gearbox, now it transfers the oil from the gearbox to engine sump, how is does it i dont know, all i can deduce is that it cant travel uphill, so there must be a secondary action causing this to happen, which the only conclusion i come to is pressurisation to the gearbox.

unless the lip seal is totally shot but this should only lose some of the oil and not all of it....as the level of oil is lower than the lowest part of the lip seal.

 

[colvic987]

FWIIW, my Hurth box breathes via the tubular dip-stick. A very small hole, ~1mm dia. drilled into one of the hexagon flats, connects with the tube. Difficult to spot if blocked with gunge, which easily happens.
The Volvo box seems to have a similar dip-stick, so might, perhaps use this arrangement.

checked the dipstick at weekend, and scraped off all the paint around the hex bolt couldnt see any sort of breather hole.

 

[Bilgediver]

Tks for your reply, this one has got me stumped, the reason i think the oil is going into the sump, is that once i have filled the gearbox with oil and the engine dipstick is at its max fill, after a couple of hours use the gearbox oil is down and the engine sump is up. my engine is on an incline down to the gearbox at the lowest level, but the engine sump is being filled, that is why i think that the oil is being sucked or pressurized into the sump....

engine oil presure guage is operating under the usual pressures depending on the revs ....

Do not forget that it takes the loss of a cup full in the gearbox to go from full mark to empty mark. A cup full in the engine would hardly be noticed on the dip stick.

You are also forgetting there is a void space between the gearbox and engine where the rubber star coupling sits. It would take many litres to fill this before any oil reached the engine and the wee drain hole at the bottom would leak to the bilges!