Cummins ISM crankcase pressure - TheDieselGarage.com
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post #1 of 8 (permalink) Old 05-01-2010, 01:00 PM Thread Starter
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Cummins ISM crankcase pressure

Trying to determine cause of high bottom end pressure. Removing oil filler cap or dipstick this engine pushes out a lot of oil smoke and gets worse as it warms up. The blowby tube discharge appears to be clear. Engine CPL is 8557; Ser#35105225. Any advice/assistance will be greatly appreciated.
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post #2 of 8 (permalink) Old 05-01-2010, 04:58 PM
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What I would do is with an adapter, put air in the intake side of the engine and put in 30 lbs, remove the valve cover first and look there are three "V" shaped areas in the rocker box intake aluminum cover, they blow out the gasket there a lot of the time, Valve guides also a possibility. Other possibilities are the turbo, air compressor, and a bad cylinder.

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post #3 of 8 (permalink) Old 05-02-2010, 01:31 AM
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If your rocker box gaskets are bad and leaking that much boost into the crankcase, you will have a good oil leak just above the head, if not, most likely in the motor. They score liners like there no tomorrow, especially if it's had a bad injector in the past for any ammount of time and if it's a high horsepower motor. 99% of the ISM's I've had with high blowby, are because of worn cylinders, the fleet I work for has a lot of M-11's and ISM's. I'd put a water manometer on it to measure the ammount of blowby, anything around 18" or so of water we'll let go, but up over 20" she's tired. Measure it so you know exactly how much there is, not just by looking at it. I've done it and been amazed by how much I thought it was huffing out the oil fill and how little it really had by the guage.

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post #4 of 8 (permalink) Old 05-02-2010, 02:26 AM
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Another quick all time Cummins check, for all their motors, is to run it at idle, hot, remove the oil fill cap and hold your hand over the oil fill. If it goes "pump-pump-pump", yank it apart. She's done... That's the only thing I ever do to test them anymore, and has never failed
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post #5 of 8 (permalink) Old 05-03-2010, 01:57 PM
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Quote:
Originally Posted by ynot View Post
Another quick all time Cummins check, for all their motors, is to run it at idle, hot, remove the oil fill cap and hold your hand over the oil fill. If it goes "pump-pump-pump", yank it apart. She's done... That's the only thing I ever do to test them anymore, and has never failed
Tonys check holds true for most engines look for puffing at the fill tube!
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post #6 of 8 (permalink) Old 05-03-2010, 04:53 PM
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If you do not have adapters and the equipment you can start it with the air intake open and restrict the flow, with the oil fill off. If if is sucking in air and now blow by then it is also the rocker box gasket. You can do it by taking off the cross over pipe and rolling the hose in to restrict. Just a thought.

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post #7 of 8 (permalink) Old 05-04-2010, 08:40 PM Thread Starter
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Thanks for all the help and advice. Road tested truck 14 miles with a jug attached to the blowby tube and accumulated a half quart engine oil. Applied shop air to the compressor inlet quickly blew oil drops out the blowby tube and smoke out the filler cap and dipstick tube. Pulled compressor off today and am awaiting replacement. Hopefully a new compressor will take of the problem. At least I'll have one good piston out of 7!!! THANKS AGAIN!
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post #8 of 8 (permalink) Old 05-05-2010, 11:06 PM
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Thats wishfull thinking, you could have just unhooked the air compressor outlet tube to make sure the compressor was unloaded and seen if the blowby changed. I hope it is just your air compressor, but I've never seen one push that much oil, the single lungers don't even puch that much air out of the discharge line, let alone just have that much leak by.

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