Measure crankcase pressure

[ArranP]

Yanmar 4JH110 any receommendations on how to measure the crankcase pressure ?

[IOM]

The question is why do you need to measure the pressure.

If you really want to proceed, then close off all the breathers, and fit a pipe and gauge to the dipstick tube.
But you need to be aware of the very real certainty of blowing out all the seals. It does make a big mess, and is very funny if you not doing the cleaning.

The volume of air is more important to know but that is not as easy to measure. All engines must breath, if they dont the pressure will rise and blow all the seals. The higher the load the more they will breath. As they get older they will breath more, its usually not a big concern.

If you feel you have a lot of crank case breathing, all you may really want to know is if one cylinder is faulty/worse than the rest and without closing all the breather pipes, just fitting a piezo type sensor on the dipstick tube and viewing the output on an oscilloscope, will tell you if there is one (or more) cylinders with a bigger displacement of air.

A better way is to take out the glowplugs and do a percentage leakage test, or at minimum check if one is leaking a lot worse than the rest, out of the breather pipes.

This way you know which cylinder is faulty, if any at all

[Ballsnall]

Put you finger lightly over the crankcase breather.

[RaymondR]

U tube manometer.

Make a U tube out of clear plastic hose with water in it. One end on the rip stick tube. If the motor has a breather between the tappet cover and the intake manifold you will have to block it. With the engine running measure the difference in height of the water column. Fresh water generates a hydristatic pressure of 0.43 psi per foot.

[ArranP]

Originally Posted by IOM

The question is why do you need to measure the pressure.

If you really want to proceed, then close off all the breathers, and fit a pipe and gauge to the dipstick tube.
But you need to be aware of the very real certainty of blowing out all the seals. It does make a big mess, and is very funny if you not doing the cleaning.

The volume of air is more important to know but that is not as easy to measure. All engines must breath, if they dont the pressure will rise and blow all the seals. The higher the load the more they will breath. As they get older they will breath more, its usually not a big concern.

If you feel you have a lot of crank case breathing, all you may really want to know is if one cylinder is faulty/worse than the rest and without closing all the breather pipes, just fitting a piezo type sensor on the dipstick tube and viewing the output on an oscilloscope, will tell you if there is one (or more) cylinders with a bigger displacement of air.

A better way is to take out the glowplugs and do a percentage leakage test, or at minimum check if one is leaking a lot worse than the rest, out of the breather pipes.

This way you know which cylinder is faulty, if any at all

I performed a compression test, the manual stipulates 464 +/- 15 psi, I got between 380 to 450 psi but my guage is not holding so I can't yet be sure of the exact maxiumum.

The engine is consuming 5 litres of oil for every 12 hours of running, producing alot of black smoke over 1500 rpm.

I inspected the turbo and found it to be damaged and swapped it out with the working tubo from the other engine. Whilst changing the tubo I found there to be alot of dripping oil and sludge in the air ducts.

I am concerned that there maybe oil entering the turbo intake from the breather pipe, hence why I would like to check for excessive crankcase pressure, and how to determine if the the pressure is excessive ?

Another idea is to remove the breather pipe from the turbe intake and place it in a plastic bottle to see if and how much oil accumulates there.

[ArranP]

Originally Posted by RaymondR

U tube manometer.

Make a U tube out of clear plastic hose with water in it. One end on the rip stick tube. If the motor has a breather between the tappet cover and the intake manifold you will have to block it. With the engine running measure the difference in height of the water column. Fresh water generates a hydristatic pressure of 0.43 psi per foot.

There is no breather between the tappet cover and the intake, but there is a breather from the base of the engine to the turbo inlet, I believe this is the breather tube for the engine. Do I block this tube whilst performing the test ? If so, am I blocking the exits so the engine cannot breather, would this not then blow all the water out of the u tube connected to the dip tube as the air has no where else to vent ?

[IOM]

If you want to see what is coming out the breather, then you can take a Coke bottle (about 2l size), (or any suitable container) push a large enough pipe to fit on the engine breather, into the bottle from near the top (cut a hole), but make the pipe go to near the bottom (1.5 inch is fine), then push pot scourers on top of the pipe at least half way up the bottle. They will break up the oil and air, and just air will come out the bottle and the oil will collect in the bottom of the bottle. If you use a coke bottle you can see the oil collecting. The reason the air is fed back into the inlet, is because it is actually exhaust gasses, so not feeding the air back into the inlet of the turbo from the bottle will result in exhaust gas in the engine compartment...just that you have been warned. The air may smell oily and yes it is CO, so dont go and sit in the closed engine room for a few hours, its been know to not be too healthy

[IOM]

There is no breather between the tappet cover and the intake, but there is a breather from the base of the engine to the turbo inlet,

Same thing , they all connected inside the engine

Do I block this tube whilst performing the test ?
If so, am I blocking the exits so the engine cannot breather, would this not then blow all the water out of the u tube connected to the dip tube as the air has no where else to vent ?

100%, it will just blow the water out the tube

You can try do this test with the water pipe on the dipstick, and leave the other pipes open. If there is a lot of pressure build up, it will still blow the water out, but thats only a small mess. Make sure the pipe is long enough, and goes down a lot before it has the U bend to perform the measurement, you dont really want the water to go into the oil

[skipperpete]

Yes there is a breather from the engine to the turbo intake as you pointed out in post 5 and the pipe going to the sump on the other side of the engine is the turbo oil drain , not a breather and from your thread about the failed turbo shaft and bearings it’s the pipe that took the metal from that failure down to the oil pan and onward to the oil filter Here’s a pic of the air intake end of the crankcase ventilation hose , the rest of it is hidden under the cover plate.

[ArranP]

Originally Posted by skipperpete

Yes there is a breather from the engine to the turbo intake as you pointed out in post 5 and the pipe going to the sump on the other side of the engine is the turbo oil drain , not a breather and from your thread about the failed turbo shaft and bearings it’s the pipe that took the metal from that failure down to the oil pan and onward to the oil filter Here’s a pic of the air intake end of the crankcase ventilation hose , the rest of it is hidden under the cover plate.

Yes this is the pipe I am referring to as the breather pipe, I am concerned that oil is coming up this pipe and into the air intake for the turbo, and then on into the air ducts and air coooler, these air ducts were dripping with oil and sludge when I swapped out the broken turbo.

[ArranP]

Originally Posted by IOM

There is no breather between the tappet cover and the intake, but there is a breather from the base of the engine to the turbo inlet,

Same thing , they all connected inside the engine

Do I block this tube whilst performing the test ?
If so, am I blocking the exits so the engine cannot breather, would this not then blow all the water out of the u tube connected to the dip tube as the air has no where else to vent ?

100%, it will just blow the water out the tube

You can try do this test with the water pipe on the dipstick, and leave the other pipes open. If there is a lot of pressure build up, it will still blow the water out, but thats only a small mess. Make sure the pipe is long enough, and goes down a lot before it has the U bend to perform the measurement, you dont really want the water to go into the oil

Thank you, any idea what tolerances are deemed as acceptable in terms of cm's or inches ?

[IOM]

Originally Posted by ArranP

Thank you, any idea what tolerances are deemed as acceptable in terms of cm's or inches ?

No Idea, I have only checked crank case pressure to see which pulse was bigger, and use electronic sensors to help me because of the high speed they offer.
Crank case breathing is usually a sign of other problems, and there are better test to find the other problems than crank case pressure.

[skipperpete]

There is no way you can do a crankcase pressure test on this engine via the dipstick tube..... well, actually there is..... take out the dipstick and start the engine, if the oil is forcibly ejected from the tube, you have excessive crankcase pressure. The lower end of the dip/ oil change tube is totally submerged in lube oil. You gain bugger all info by knowing the actual pressure especially if it’s high enough to pressurize the turbo drain pipe to the point where it’s causing the turbo seals to leak..... but remember, they leaked because “ the turbo shaft was buckled”. This is an over €1 million catamaran, and since you’re in Thailand you need to get the Yanmar pro’s from Phuket to take a look into this because you do need professional help. Is this a charter boat by any chance? there were two of these in the marina in Langkawi across from my boat.

[ArranP]

Originally Posted by skipperpete

There is no way you can do a crankcase pressure test on this engine via the dipstick tube..... well, actually there is..... take out the dipstick and start the engine, if the oil is forcibly ejected from the tube, you have excessive crankcase pressure. The lower end of the dip/ oil change tube is totally submerged in lube oil. You gain bugger all info by knowing the actual pressure especially if it’s high enough to pressurize the turbo drain pipe to the point where it’s causing the turbo seals to leak..... but remember, they leaked because “ the turbo shaft was buckled”. This is an over €1 million catamaran, and since you’re in Thailand you need to get the Yanmar pro’s from Phuket to take a look into this because you do need professional help. Is this a charter boat by any chance? there were two of these in the marina in Langkawi across from my boat.

No its a family boat, it was purchased salvaged, sank in Vietnam.

[skipperpete]

That changes things a bit. I guess the best course of action from here is to buy a new turbo, strip off the intercooler and pipework for a thorough clean up, change the engine oil and open up the filter paper for inspection (turbo shaft and bearing debris)...... Then do a run up and unscrew the oil filler cap to settle the “crankcase pressure” debate, you WILL know the answer immediately the cap is loosened. Maybe do the valve clearances too, at the rate of oil consumption you posted, the engine will probably be well and truly coked up.