Yanmar 3qm30f started leaking oil from multiple places.

[Compass790]

Glad you updated post & good news your engine doesn't have much blowby so unlikely to be a ring problem as I suggested as a possibility earlier. Can't see it being a breather problem either if you could blow out the restriction. Still puzzled about the sudden onset of the symptoms. Looking fwd to you finding the smoking gun.
The sump cover that the breather pipe comes out of before it goes into air intake on our yammer has a wire mesh screen inside it that could be clogged with sludge IMO. I cleaned that with degreaser on rebuild so if your engine has similar setup it's worth a try to clean it. After all breather pipe cant breathe if it's source filter is clogged. You may have trouble blowing back the other way.
The sump on our engine had lot's of sludge in it after 37 years although the engine was supposedly reconditioned.

[jimbunyard]

Sounds like you have found the smoking gun. Though there is little backpressure with the filler cap off, with a well-sealed engine, pressure will build up as the engine runs if not bled off, either to the intake or the atmosphere.

Though there isn't one shown in the parts manuals I've seen, there is enough real-world experience here to show there's a screen behind the breather cover bolted to the block just above the fuel pump.

For me the next move would be to remove the cover (item 73, 6 bolts), clean the screen (wash in diesel), and replace with a new gasket.

Wouldn't be surprised if the problem went away...

[Compass790]

Correction:Sorry I failed to mention our Yanmar is a YSM8 not a 3QM30 so may have a different sump breather setup than yours i.e, maybe no mesh screen. Maybe worth a try just blowing through to see if it's clear.
Jim Bunyards post #17 reminded me not to assume all Yanmars are the same though often different models share some common parts.

[ramblinrod]

Originally Posted by Nth

I have an old 3qm30f that still starts and runs well but has suddenly (within a week) developed a large oil leak from multiple places. Looks to be coming from around the fuel pump, maybe front cover and the valve cover gasket. Definitely one spot on the lower front and one up the upper mid to back side.

My first thought is excessive crank pressure but before I tear into it wanted to get opinions and advice. Can I even get gaskets, rings, bearings and (I believe) sleeves for this engine? Only other complaint is it idles great and will run smooth at high rpm but runs rough in between. It's been that way since I've owned it so probably unrelated.

Thanks!

All 3GM30F parts are available from a Yanmar dealer.

The predecessor, 3GMF had cylinder sleeves and delivered 22 HP. After a few years of production it was revised to make the 3GM30F, cylinder liners we’re removed, cylinders bored out, and larger pistons put in.

If you can get your hands on a 3GMF do it! Great engine that will run forever and can be completely rebuilt with no machining.

[Wotname]

Originally Posted by ramblinrod

All 3GM30F parts are available from a Yanmar dealer.

The predecessor, 3GMF had cylinder sleeves and delivered 22 HP. After a few years of production it was revised to make the 3GM30F, cylinder liners we’re removed, cylinders bored out, and larger pistons put in.

If you can get your hands on a 3GMF do it! Great engine that will run forever and can be completely rebuilt with no machining.

Not sure how this relates to the OP's 3QM30F and IMHO, the 3QM30 is even better than the 3GMF.

[Wotname]

Originally Posted by jimbunyard

Sounds like you have found the smoking gun. Though there is little backpressure with the filler cap off, with a well-sealed engine, pressure will build up as the engine runs if not bled off, either to the intake or the atmosphere.

Though there isn't one shown in the parts manuals I've seen, there is enough real-world experience here to show there's a screen behind the breather cover bolted to the block just above the fuel pump.

For me the next move would be to remove the cover (item 73, 6 bolts), clean the screen (wash in diesel), and replace with a new gasket.

Wouldn't be surprised if the problem went away...

A picture says a thousand words.

This what is on the inside of item 73. The hole marked drain in picture is at the bottom (picture is reversed).

There is one baffle visible so I guess there are others under the metal cover or maybe some coarse mesh.

The metal cover is welded on at each end so there is no easy way to look underneath it.

If it was me, I would simply flush with solvent and blow air though it both ways or I might grind the welds just to see what is really there

Excuse the rusty surfaces, this part is from a QM that making serious quantities on milky oil and the sat for a couple of years under a house before I ended up with it.

[Nth]

Wotname, the diaphragm in my pump was near mint so I'm just replacing the oring and seal but if you need one check ebay for RG60081. It looks like the same pump except for the actuator arm. I can't guarantee it'll fit but for $35 worth a shot.

TBH, if my pump was bad I'd plate off the hole in the block and replace it with a cheap 12v electric lift pump. As I type this now I'm still considering it. It'd add electronic run-away control, make bleeding effortless, eliminate a place where fluids can mix, provide a lot more volume... ugh. Might be talking myself into it.

[Wotname]

Originally Posted by Nth

Wotname, the diaphragm in my pump was near mint so I'm just replacing the oring and seal but if you need one check ebay for RG60081. It looks like the same pump except for the actuator arm. I can't guarantee it'll fit but for $35 worth a shot.

........

Thanks for the tip!

[ramblinrod]

Originally Posted by Wotname

Not sure how this relates to the OP's 3QM30F and IMHO, the 3QM30 is even better than the 3GMF.

Whoops.

I mistook 3qm30f for 3gm30f

In lower case, they are pretty similar looking.

The actual model number is 3QM30F (all upper case).

I don't encounter many 3QM30Fs and am not sure of the parts availability. Being older, and smaller install base, I would still recommend a 3GMF, or a 3GM30F if higher HP is needed. I absolutely adore these engines.

[Nth]

Update, found the top-end leak. It was the rear decompression lever's shaft. The return spring hid it from sight.

I also took off the breather plate above the injection pump and blew carb cleaner through it. I couldn't get at the screen without grinding off the baffle. Hopefully that will be enough.

As for the lower leak I removed the mechanical lift pump. I believe the leak was coming from the pump but haven't ran the engine to confirm. I'm still waiting on parts from the Yanmar dealer.

If it's not the pump then I'm probably looking at replacing the front cover gasket. Could be worse.

[Wotname]

Thanks for the update, it always good to know how these things get sorted out

[sfnz]

i have a 2QM20F that is in pretty good nick for its age, gave it a coat of paint to dolly it up (white so any leaks' show) bench ran it and worked a charm.....for a while... then did the most effortless self oil change I have ever seen a diesel do out the dipstick hole, the dipstick was ejected a few feet followed by a spout of oil.... everything was on the engine except for the crankcase breather tube which was removed and blocked up at the injector end for painting, so other than the breather tube the only real pressure relief is via this hole, lucky it was fresh oil I was mopping up !!!.....lesson learnt

[dreuge]

It’s been a while, but I wanted to add info for future reference. I rebuilt a 3QM30 and posted details on my blog(link below). Saved a bunch of cash buying as many Yanmar parts from Hoye Tractor.

http://svjohannarose.blogspot.com/search/label/EngineWork?m=1