Measure crankcase pressure

[Ballsnall]

Originally Posted by ArranP

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.

Simply take the breather off whilst the engine is running, excessive blowby will be obvious. You don't need to measure it, just compare it with the other engine if you your unsure..

A simple and definitive test is to do two compression tests, (with a working gauge) run the compression test as normal then run a second test but with a light lubricant added to each cylinder and compare the results, a higher reading on the second test indicates worn rings causing excessive blowby.

Your initial test reading of 380 psi suggests at least one cylinder is down and adding a lubricant will tell if it is due to rings (test pressure will increase) or valves (test pressure will be consistent)

[ArranP]

Originally Posted by 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.

Thank you, I have swapped out the turbo with the one from the working engine on the other side, and will clean out the air ducts and air coooler with degreaser once it arrives.

What is the filter paper ? Is this the oil filter yanmar part no 129150-35170 ?

[skipperpete]

Yes, if there’s a major engine incident like you just had, it’s often prudent to cut open the filter canister and inspect the paper folds for metal particles, too much rubbish can block the filter and trigger the bypass which allows unfiltered oil to flow through the system. If I was the bloke you were paying to fix this engine, you wouldn’t appreciate a crankshaft bearing seizure immediately after I fitted a brand new turbo because I missed the possibility that there was other stuff happening downstream of the turbo lube circuit.
You can buy a special tool to open the filter can.... specifically for that job.

[skipperpete]

Oh, if want a turbo fairly quickly, maybe contact Minards Diesel in Australia, great service with spare parts if you want to use original Yanmar stuff (and complete engine packages) delivered to Malaysia and Thailand.

[ArranP]

removed the oil filler cap, is this excessive blowby / crankcase pressure.

video https://photos.app.goo.gl/R6aqtRsyecWoTCuh7

when engine revs up the cap settles down, is that odd ?

[skipperpete]

Crankcase pressure in the video looks not too bad, I’d suggest not enough to backup the turbo drain and cause the shaft seals to leak. As long as the hose from the rocker cover to the turbo intake screen is open there should be no dramatic pressure increase. If you want to further test the pressure buildup, put the filler cap back on and block the breather pipe to the turbo intake screen with your thumb. If the pressure rises (and keeps rising) significantly there’s a compression leak, usually piston ring issues but occasionally possible that the head gasket has blown across to the pushrod gallery. ( this usually shows as more of a puff puff symptom)

[ArranP]

Originally Posted by skipperpete

Crankcase pressure in the video looks not too bad, I’d suggest not enough to backup the turbo drain and cause the shaft seals to leak. As long as the hose from the rocker cover to the turbo intake screen is open there should be no dramatic pressure increase. If you want to further test the pressure buildup, put the filler cap back on and block the breather pipe to the turbo intake screen with your thumb. If the pressure rises (and keeps rising) significantly there’s a compression leak, usually piston ring issues but occasionally possible that the head gasket has blown across to the pushrod gallery. ( this usually shows as more of a puff puff symptom)

Thank you I will perform the test of putting my thumb on the breather pipe with the cap closed the next time I am at the boat.

I have been thinking....

The engine has been making black smoke from before I set out on the 1300 mile passage from Vietnam to Thailand. It does not make this smoke whilst in neutral but only when in gear and the engine won't rev past 1900 rpm when in gear but will rev to 3500 rpm whilst in neutral, above 1500 rpm whilst in gear is when the black smoke comes, otherwise the exhaust smoke is clear.

So I kept the revs to 1500 rpm for the trip from Vietnam to Thailand.

It was only from Penang onwards that the high oil consumption began, at the rate of 5 litres for every 12 hours of running.

Could it be that the high oil consumption was due to the broken turbo and that the black smoke is a seperate issue caued by shaft mis-alignment or propellor being incorrectly re-installed ? The propellors were removed to replace the cutlass bearings in Vietnam before setting out, and one of the engine mounts is defective, a strap has been used to keep the engine in place.

I am considering that the excessive oil consumption and the black smoke maybe seperate issues. The black smoke began before the high oil consumption, it could be that now the turbo has been changed the oil consumption will return to a nominal level, and that the black smoke is being caused because the engine cannot turn the prop any quicker hence it maxing out at 1900 rpm ? I suppose to determine this I would need to check the shaft alignment and / or disconnect the folding propellor from the shaft, or bind the propellors closed so it does not open when I give the engine revs ?

How can there be high oil consumption if there is no crankcase pressure or blowby, for high oil consumption there would need to be defective rings and high crankcase pressure, or a leaking turbo. Now the turbo has been changed for the turbo from the other engine the oil consumption should return to normal considering there is little crankcase pressure ?

Trying to seperate the issues and determine a way to progress forward.

The local Thai mechanic took one look and wants to pull out the engine to replace the oil rings, however I am uncertain that this is necessary.

Here is a video of the black smoke when first setting out from Vietnam https://photos.app.goo.gl/JYyxXatEM1AKoJWs7
The broken turbo has now been changed, but the black smoke still comes when in gear agove 1500 rpm, and the engine still wont rev past 1900 rpm... maybe I should bind the folding prop closed and try it to see if the revs go higher and the black smoke dissappears, as it does when in neutral.

When in neutral the engine revs to 3500 rpm and exhaust is clear.

[FPNC]

Originally Posted by ArranP

Thank you I will perform the test of putting my thumb on the breather pipe with the cap closed the next time I am at the boat.

I have been thinking....

The engine has been making black smoke from before I set out on the 1300 mile passage from Vietnam to Thailand. It does not make this smoke whilst in neutral but only when in gear and the engine won't rev past 1900 rpm when in gear but will rev to 3500 rpm whilst in neutral, above 1500 rpm whilst in gear is when the black smoke comes, otherwise the exhaust smoke is clear.

So I kept the revs to 1500 rpm for the trip from Vietnam to Thailand.

It was only from Penang onwards that the high oil consumption began, at the rate of 5 litres for every 12 hours of running.

Could it be that the high oil consumption was due to the broken turbo and that the black smoke is a seperate issue caued by shaft mis-alignment or propellor being incorrectly re-installed ? The propellors were removed to replace the cutlass bearings in Vietnam before setting out, and one of the engine mounts is defective, a strap has been used to keep the engine in place.

I am considering that the excessive oil consumption and the black smoke maybe seperate issues. The black smoke began before the high oil consumption, it could be that now the turbo has been changed the oil consumption will return to a nominal level, and that the black smoke is being caused because the engine cannot turn the prop any quicker hence it maxing out at 1900 rpm ? I suppose to determine this I would need to check the shaft alignment and / or disconnect the folding propellor from the shaft, or bind the propellors closed so it does not open when I give the engine revs ?

How can there be high oil consumption if there is no crankcase pressure or blowby, for high oil consumption there would need to be defective rings and high crankcase pressure, or a leaking turbo. Now the turbo has been changed for the turbo from the other engine the oil consumption should return to normal considering there is little crankcase pressure ?

Trying to seperate the issues and determine a way to progress forward.

The local Thai mechanic took one look and wants to pull out the engine to replace the oil rings, however I am uncertain that this is necessary.

Here is a video of the black smoke when first setting out from Vietnam https://photos.app.goo.gl/JYyxXatEM1AKoJWs7
The broken turbo has now been changed, but the black smoke still comes when in gear above 1500 rpm, and the engine still wont rev past 1900 rpm... maybe I should bind the folding prop closed and try it to see if the revs go higher and the black smoke disappears, as it does when in neutral.

When in neutral the engine revs to 3500 rpm and exhaust is clear.

You are describing excessive exhaust back pressure. Turbos hate back pressure. If the exhaust back pressure is too high, it will push exhaust past the turbo shaft seal and then push turbo oil into the intake.

Excessive exhaust back pressure will cause all the symptoms you have described.

[Ballsnall]

Originally Posted by ArranP

removed the oil filler cap, is this excessive blowby / crankcase pressure.

You have no discernible blowby.

when engine revs up the cap settles down, is that odd ?

Perfectly normal, that's just the engine vibration dampening down.

[skipperpete]

So initially there was only the “black smoke” problem which then developed into a bent turbo shaft (and severely damaged turbo) and substantial lube oil consumption coupled with what must be a seriously compromised induction system.... (the airflow through the intercooler must be very restricted). I reckon the turbo was buggered in Vietnam and your engineers first priority upon seeing a sooty exhaust was to remove the intake filter screen from the turbo and manually try to rotate and wiggle the compressor wheel and maybe review the exhaust system and mixer elbow...... NOW, after 1300 miles you have secondary symptoms and damage, certainly a clogged intercooler but more importantly a severely coked up engine.... possibly in both the exhaust ports and the intake ports. I don’t think there’s a real easy fix for this but I’m thinking it might be worth lifting off the head to see what’s going on with the ports and valves.
I’m in the area so PM me if you want any more info.
Pete.

[Ballsnall]

Originally Posted by ArranP

The engine has been making black smoke from before I set out on the 1300 mile passage from Vietnam to Thailand. It does not make this smoke whilst in neutral but only when in gear and the engine won't rev past 1900 rpm when in gear but will rev to 3500 rpm whilst in neutral, above 1500 rpm whilst in gear is when the black smoke comes, otherwise the exhaust smoke is clear.

The black smoke is from over fueling not oil consumption. Your engine is overloaded that's why it won't go over 1500 rpm.

It was only from Penang onwards that the high oil consumption began, at the rate of 5 litres for every 12 hours of running.

Your turbo seals failed, no engine would be able to run at 5l/h blowby.

Could it be that the high oil consumption was due to the broken turbo and that the black smoke is a seperate issue caued by shaft mis-alignment or propellor being incorrectly re-installed ? The propellors were removed to replace the cutlass bearings in Vietnam before setting out, and one of the engine mounts is defective, a strap has been used to keep the engine in place.

Almost certainly a separate issue. Was the engine issue apparent prior to haul out?

Hard to imagine shaft misalignment as the issue, but easy to check to rule out.

Folding prop, yes if it was disassembled and reassembled incorrectly. Pull the prop and check assembly. One test you could do would be to run the boat on each engine separately at the same revs and compare boat speed.

Engine mount, no.

Now the turbo has been changed for the turbo from the other engine the oil consumption should return to normal considering there is little crankcase pressure ?

Yes, oil consumption should be fine now.

The local Thai mechanic took one look and wants to pull out the engine to replace the oil rings, however I am uncertain that this is necessary.

Very premature, conduct a quality cylinder pressure test including wet test, that will guide you on engine condition. No decent mechanic would advise an engine rebuild without doing these tests first.

[skipperpete]

Excellent post Ballsnall, especially the remarks about the propeller, a Gori 2 speed prop locked in overdrive would cause substantial black smoke right from the relaunch.

[ArranP]

Originally Posted by FPNC

You are describing excessive exhaust back pressure. Turbos hate back pressure. If the exhaust back pressure is too high, it will push exhaust past the turbo shaft seal and then push turbo oil into the intake.

Excessive exhaust back pressure will cause all the symptoms you have described.

Thank you, how can I test for this ? by removing the mixing elbow then run it at full revs, if the rpm goes above 1900 it is likely that there is a blockage/restriction at or after the mixing elbow.

[ArranP]

Thank you.

Originally Posted by Ballsnall

Almost certainly a separate issue. Was the engine issue apparent prior to haul out?

Prior to haul out the vessel had sunk, it was later refloated, engines and transmissions were removed, dissassembled, cleaned, bearings replaced and reassembled and re-installed back into the boat.

Prior to sinking there was just a few hundred hours on the engines.

Originally Posted by Ballsnall

Hard to imagine shaft misalignment as the issue, but easy to check to rule out.

I'd be happy to follow instruction on how to check the shaft alignment. The transmission is a v-drive ZF63IV.

Originally Posted by Ballsnall

Folding prop, yes if it was disassembled and reassembled incorrectly. Pull the prop and check assembly.

There is 4cm visibility, would it be an effective test to bind the folding prop closed with rope then see if the rpm can go over 1900 ? Would this be a sufficient indicator that the prop is the problem ?

Originally Posted by Ballsnall

One test you could do would be to run the boat on each engine separately at the same revs and compare boat speed.

There is one working turbo and transmission at the moment.

[Ballsnall]

Originally Posted by ArranP

Thank you.

Prior to haul out the vessel had sunk, it was later refloated, engines and transmissions were removed, dissassembled, cleaned, bearings replaced and reassembled and re-installed back into the boat.

Prior to sinking there was just a few hundred hours on the engines.

Ok, I'm getting a clearer picture now. Were the engine's fully striped and rebuild or just bearing replaced? I would definitely get a compression test done and injectors checked.

I'd be happy to follow instruction on how to check the shaft alignment. The transmission is a v-drive ZF63IV.

Sorry, no experience with the V drive but I believe the alignment is the same method.
Disconnect the prop shaft and use feeler gauges to check alignment. Probably very difficult or even impossible as it will be under the engine.

There is 4cm visibility, would it be an effective test to bind the folding prop closed with rope then see if the rpm can go over 1900 ? Would this be a sufficient indicator that the prop is the problem ?

It might work but I would just remove the prop, shouldn't be too difficult even in zero viz.

There is one working turbo and transmission at the moment.

Ah, ok. Have you tested it with the other turbo fitted?