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Volvo TAMD 41P Oil Leaking From Turbo Charger??? Crank case pressure??

jziegler

New member
New to forum. I have twin 200 HP Volvo TAMD 41P in my boat. Both were completely rebuilt in 2011 with all Volvo OEM parts - new pistons, liners, rings, etc. Used the boat for a year (about 100 hours worth) with no problems. Then, pulled boat and it sat on a trailer in my lot for 1.5 years. Now, trying to get her running again.

Launched boat last week and did a sea trial. Observed the Port engine max'ing out at 2400 RPMs. Starboard engine ran perfect. Noticed the port engine turbine was frozen - probably from sitting for long time. We tried to free it with socket wrench and broke the nut and shaft - I know, stupid move.

Had turbo rebuilt and reinstalled. Sea trial again. Boat ran great - smooth, no smoke, both engines max'ed out at 3600-3700 RPMs, good temp around 160 degrees. Oil pressure at cruising (2800 RPMs) was 60 to 70 PSI. Port engine was slightly higher (70 PSI) vs. 60 psi on starboard. Thought all was good. But then,

Observed small but continuous oil leaking from exhaust side of turbo and rear main seal. Noticed crankcase pressure by removing oil fill cap and holding hand over the hole. There was pressure from breather 1/4" tube also that I have routed to air filter on turbo compressor. The guy who rebuilt the turbo said that crank case pressure was not allowing turbo oil return to drain so it leaked out the tubo exhaust side. I removed the return line from the turbo, put my finger over the return, and started engine. I felt hi pressure from the turbine return (should be low pressure gravity return, right?) and could not hold closed - oil blew out under pressure. So, my reasoning was that the turbine pressurized return was cause of crankcase pressure - turbine problem. But, turbine guy says it is an internal engine problem and his recently rebuilt turbine is fine.

Next tested compression: 1 was 475 PSI, 2 was 460 PSI, 3 was 475 PSI, 4 was 400 PSI, 5 was 450 PSI, and 6 was 500 PSI. My diesel mechanic thinks turbo rebuild may be bad and the source of turbo oil leak and crankcase pressure. Turbo rebuild guy thinks there is an internal issue (blowby?) with engine causing crankcase pressure which in turn is blowing oil out rear main seal and not allowing turbo return to drain fast enough (hence if leaks into exhaust).

Any thoughts or suggestions? Anything to do to get more clues. I'm still hopeful I don't need to rebuild engine but cylinder 4 has me worried.


Thanks. Joe
 
You have 2 identical engines?? Isolate the problem area by moving the suspected turbo to the other engine.
If it did not move the leak to the other engine, move the good turbo over and determine if you do have a compression leak or some other problem like plugged return line etc. It is always possible something like a piece of foreign material has cause a restriction somewhere. Blow-by would be evident elsewhere as well, such as excessive dip stick pressure, which you might be able to compare.
If the rebuilt turbo seals are damaged moving the good turbo to the problem side could result in the same problem leak, a risk, but you would have your answer.
 
Thanks. Yes, I had the same idea. But, I have one good engines with no issues that I don't want to mess with. And, I need to buy turbo-to-engine gaskets (they are one-and-done). But, probably will be doing that. Trying to rule out all the simpler things first.

Do you know if there is supposed to be pressure on the turbo oil return? Turbo rebuild guy says there should be none? I disconnected turbo return and put my finger over the turbo oil return port. Started engine and felt major pressure - oil squirted out similar to finger over garden hose???

Also, what do you think about my cylinder pressures - especially number 4?

Thanks. Joe
 
The oil feed to your turbo is under pressure, so the return line must also be under pressure if you try to block it. If it is freely flowing back to the sump however there won't be much pressure in the return pipe. This is normal. Your turbo won't cause your blowby. That is a function of your pistons/rings (usually). If you have significantly more blowby on one engine than the other, you may have internal wear issues. In our case (pair of KAD32's) it was a bunch of 2nd rings that broke (issues with the factory rings in some years) so we had blowby without losing that much compression.

I am not sure that I understood your explanation properly, but if you are having oil leak past the rear oil seal in the turbo, that is unlikley to be anything other than a bad seal issue. What I can't work out is where you are seeing the oil appear as it should be staying inside the exhaust system if leaking through the turbo seal. There is no where that it should become visible?

What you do need to do though is check whether your crankcase breather is allowing the crankcase to 'de-pressurise'. If it is blocked or somehow allowing the crankcase to build excess pressure you may eventually have issues like the dipstick popping out and oil coming out of the dipstick hole.
 
The oil is leaking out the exhaust side of the turbo. We noticed it around the exhaust elbow C-clamp. Some manages to come out and run to underside of turbo. If you take exhaust elbow off, you see much more.

The turbo has oil feed in and oil return out to the pan. So not all the oil coming in is going out the return. Some is leaking out the turbo exhaust side. What is the rear oil seal in the turbo?

Already checked breather - it blows a steady low pressure air (no oil) back into the air filter on the compressor side of the turbo. No clogs on that. No clogs on the turbo oil return either. There is no oil blow by that I can see.

Another thing - the frozen turbo did not leak oil. First sea trial, we discover frozen turbo; remove it but see no oil leaking into exhaust. Second sea trial, with rebuilt turbo, we see oil leaking from turbo. Take back to turbo shop - they dismantle, check, and give back saying nothing wrong. Reinstall, sea trial 3, and still oil coming from turbo exhaust?? Also, on third sea trial, we see small oil leak from rear main seal too (coincidence or from problem causing crank case pressure)?
 
I have been assuming that the oil leaking out my exhaust elbow is coming from the turbo. But, is there anyway, the oil could be in the exhaust? I would think the exhaust would be too hot to pass liquid oil - rather, it would be smoke, right? But, the oil is coming out at the elbow connection to the turbo so I thought I would ask the question.
 
I can't think of anywhere that pressured oil and the exhaust come together other than the turbo. Oil in the exhaust system prior to the turbo would most likely get burned and appear as blue smoke. Fram what you have posted the turbo oil seal still appears the most likely issue.

An over-pressurised crank case might cause a rear main (crank shaft) seal leak, but I can't think of how that would link to your turbo oil leak issues. I imagine that the rear main seal is a typical 'lip seal' and if so it would be unusual for one to fail so so after being replaced. One possible explanation would be if there was corrosion on the shaft from sitting, but that is unlikely after just 18 months. Another possibility is that there had been previous corrosion, and/or the old seal has worn a groove into the shaft prior to the rebuild. In those cases it is not unusual for a new seal to last OK for a short period before failing.
 
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