Yanmar 2GM20 oil exploding from dipstick hole

[Kita]

Originally Posted by sfnz

same engine and same thing happening, looks like the oil pressure regulator (naturally an obsolete part as I have tried to get one !!!) the 3QM though slightly different valve design fits and has the same pressure setting however...yep that's obsolete as well, have been thinking of trying a 2GM one but they have 10psi more pressure, to check it, unwind the oil filter and then the big nut (32mm from memory) that is on the shaft that the filter threads on , with that lose the threaded part screws out and that's your oil pressure regulator, do you have a manual for this engine ?

Replace the sensor first,they go bad alot,it's easy & cheep & usually that will take care of it unless there really is a problem which I kind of doubt

[sb1]

Originally Posted by a64pilot

You know if I was to pull the head, I would have the valves done and new seals fitted, that ought to buy you at least another 20 years until the seals dry out and need replacing.
When your have the head off inspecting the cylinder bores can give you a very good idea where you are in terms of how long before an overhaul will need the be thought about

I like the thought of my engine outliving me! I will take that advice, thanks.

[Jpernick]

I have a 3gm with very similar issue. At high rpm I build crank case pressure that results in oil leaking from dip stick and seals.

I have removed the short breather hose and replaced with a longer hose that I have routed into the air intake of the flame arrestor. Any escaping crank case gas in ingested by the engine as it should be.

This has solved the problem of pressure build up. I'm still not sure if my blow by is too excessive for the system that leads into the intake manifold or if the intake manifold end of the pressure relief system is blocked.

Does anyone know....
How to quantify excessive blow by?
How to test the manifold pressure relief system?

Jeff

[a64pilot]

There is no relief system per se, just a hose connected to the valve cover, very often there is at least a baffle to keep liquid oil from being splashed out the breather, often there is also something like steel wool, baffles and or steel wool can get sludge build up and need cleaning, sludge builds on the cooler parts of an engine, basically oil vapor condenses there and valve covers are about the coolest part.
There is a method of measuring crankcase pressure in aircraft using a manometer, but without having limitations I don't know what good knowing what your crankcase pressure is.
You can remove and clean the valve cover ensuring the oil separator is clean, sometimes it can be disassembled, but often all you can do is soak in mineral spirits

[a64pilot]

Originally Posted by sb1

I like the thought of my engine outliving me! I will take that advice, thanks.

Once the head is off, you can inspect the bores. You can borescope maybe without removal, but nothing beats dragging your fingernail and seeing if there is enough ridge to catch a nail in my book

[Jpernick]

When the breather hose is disconnected from the valve cover excess pressure exits the valve cover and there is no pressure in the crank case. When the tube is hooked up pressure builds up at high rpm. So, I don't know whether there is too much blow by to be accommodated by the intake manifold nipple or if the nipple is just plugged. I think I need a blow by spec and a way to measure gas volume from the breather.

[a64pilot]

If pressure dissipates with hose disconnected from breather, then you have a restriction there, have to.

[a64pilot]

It actually connects directly to the manifold?

[Dymaxion]

Originally Posted by Jpernick

I have a 3gm with very similar issue. At high rpm I build crank case pressure .........
<snip>
Does anyone know....
How to quantify excessive blow by?
How to test the manifold pressure relief system?

Jeff

You can use a leak down tester to give a better analysis of how any engine is losing compression. Good one is $50-60. Need a proper air compressor to operate, they work by putting compressed air into the cylinder via plug/ injector. Put/hold the piston at TDC and leakage out is past worn rings or exhaust valve or intake valve, or all of the above. Listening at intake will hear the hiss of a bad intake valve, etc. Blowby can be heard at the dipstick. A pressure gauge on the unit indicates leak down extent, usually as green/yellow/red bands. Easy to use, use it with cold and hot engine, add oil to cylinder for temporary ring reseal and isolate rings from valve leakage.

[Wotname]

Originally Posted by a64pilot

It actually connects directly to the manifold?

Yes for a 2GM20, just after the air filter.

[a64pilot]

Originally Posted by Wotname

Yes for a 2GM20, just after the air filter.

There is danger in that, a worn engine will often carry a little oil in it blow by gasses and a Diesel will run on crankcase oil, so if worn enough to carry enough oil, it could run away, especially if someone overfills the crankcase by accident.
It may be worth considering fitting a catch can, they can be very simple, the one I had on my Drag Bike back in the late 70's was a Mountain Dew can. It sat on the swing arm and drew a lot of attention, there were many theories of what that Mountain Dew can really was

[sb1]

Originally Posted by Jpernick

...I don't know whether there is too much blow by to be accommodated by the intake manifold nipple or if the nipple is just plugged.

I pushed a needle through that small aperture and it seemed clear, although that whole are is a little coked.

[Wotname]

Originally Posted by a64pilot

There is danger in that, a worn engine will often carry a little oil in it blow by gasses and a Diesel will run on crankcase oil, so if worn enough to carry enough oil, it could run away, especially if someone overfills the crankcase by accident.
It may be worth considering fitting a catch can, they can be very simple, the one I had on my Drag Bike back in the late 70's was a Mountain Dew can. It sat on the swing arm and drew a lot of attention, there were many theories of what that Mountain Dew can really was

I'm sure the Mountain Dew can suited your drag bike ; but no Mountain Dew can is going into this engine space .

The crankcase ventilation is at the top of the photo in the middle and heads off to the right. Some reason I now forget, the air cleaner was removed when the photo was taken.

[CareKnot]

That may be one of the cleanest engine rooms I've seen in a while. Mine currently looks like a steam-punk, mechanized Porta-Potty. Lotsa work ahead of me...

[a64pilot]

I had assumed an old, worn engine.
Surely the fitting screws in? If so unscrew it and I bet you will find it gunked up, I assume it should have roughly the same internal diameter as the hose.
If there is no pressure build up with the hose disconnected, then there has to be a restriction with it connected. I can think of no logical reason there should be a restricted orifice on a Diesel engine. A spark ignition engine would have a restricted orifice as this would be a vacuum leak, AKA unmetered air, this restricted orifice is often called a PCV valve, but I have never seen a Diesel with a PCV valve or other restricted orifice. A spark ignition engine has vacuum in the intake manifold as of course there is a throttle valve, a Diesel has no throttle valve, and therefore no manifold vacuum.
Diesel powered automobiles have to come up with another way to power those items that are normally powered by vacuum on a regular car like power brakes, air conditioner controls, cruise control etc. for example