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855 Turbo Oil Leak

Posted By Ol' Kenny Thursday, August 01, 2019 1:21 PM
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Ol' Kenny
 Posted Thursday, August 01, 2019 1:21 PM
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Hi Guys,

I have been stumped by a minor oil leak on my 855....I can't handle this small leak on a fresh re-build. Oil appears to be leaking from the connection where a homemade pipe thread to SAE thread fitting adapter threads into the bottom of the turbo (see attached picture) but it is difficult to see for sure because the fitting goes through the shroud that connects the inlet and outlet turbo housings. I have tried everything to get the pipe thread connection to seal up.....teflon tape, pipe dope, permatex thread sealant, and permatex black rtv silicone. Somebody definitely welded up a a homemade adapter using a cut off pipe nipple and SAE fitting. Is there a Cummins part number for this adapter fitting that is supposed to be there? I also made a new turbo drain hose thinking that it could have been blocked or kinked but there was no improvement. Thanks in advance for any guidance that you can give me!
 IMG_7973.pdf (109 views, 6.43 MB)
Geoff Weeks
 Posted Thursday, August 01, 2019 2:20 PM
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I wonder if your hose is too small. My 855 Turbo has a 1/2 or 3/4" NPT to 7/8 tube drain, that hose looks considerably smaller than that.
edit:
Also the drain must slope down with no low spots to collect a pool of oil. All mine have either a tube with a 2 bolt flange at the turbo, or a pipe thread with a 45 deg fitting to an inverted flare tube, both use a short piece of hose at the block connection.
Friday, August 02, 2019 4:29 AM by Geoff Weeks
Newto
 Posted Saturday, August 03, 2019 10:26 PM
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The drop from the bottom of the turbo to the bend in the hose is more than adequate.....if you had a blockage or slow drainage you would have flooding of the centre bearing housing and oil migrating out the exhaust and also into the intake so that's not it.

Are you sure that the inlet oil fitting isn't the problem or the oil supply line connection because the oil can leak from the top and run down around the centre housing to the drain.....just a thought.

That drain fitting into the turbo centre bearing housing should be a tapered gas thread as standard.If its not then someone has stuffed it up.

the p/n for the long straight drain fitting with a flare connection to a flexible hose is 196932.

it looks very much like the fitting you already have out of the turbo except its brass & doesn't have that extra nipple adaptor between it and the hose.Hose should be no12 aeroquip but that's not the problem.

Newto
Saturday, August 03, 2019 10:41 PM by Newto
Geoff Weeks
 Posted Sunday, August 04, 2019 1:38 AM
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Newto's post made me think of one other thing. If inlet fitting uses an O ring, the std O ring from a hyd fitting will not stand the heat and you need a high temp O ring (Viton or similar material)
Sunday, August 04, 2019 1:39 AM by Geoff Weeks
Newto
 Posted Sunday, August 04, 2019 10:42 AM
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Geoff,

That turbo is an old VT/ST model that used tapered threads top and bottom.

Doesn't mean that it can't be loose or the flare damaged though.

You're obviously a later model than me (hehe) because the oring fittings weren't around on early Cummins turbo's until Holset turbo's were standard.

Newto
Sunday, August 04, 2019 10:42 AM by Newto
Geoff Weeks
 Posted Sunday, August 04, 2019 1:07 PM
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Yeah, my experience is limited to the Big cams, and mostly to the later Big Cams. Did find out about the Viton the hard way when I replaced an oil line on the road, they only had JIC fittings for the hose, so it got a hose and fitting change, I forgot to tell them it was going on a turbo, so the JIC to O ring boss fitting had regular O ring, didn't last long and was leaking oil again, Viton O ring and all was good.
Ol' Kenny
 Posted Saturday, August 10, 2019 7:24 AM
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Thanks for the info guys, I've been out of town for the past few weeks and haven't had a chance to take a look yet. Tomorrow I will check out the inlet fitting.....good point, it could be tricking me with the oil running down the turbo behind the shroud and just appear to be coming out of the outlet. Thanks for the part number on the outlet fitting. If the oil leak persists I will change that out. I'll report back with the results!
Ol' Kenny
 Posted Monday, August 12, 2019 4:17 AM
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Well, I am embarrassed. It appears to have been leaking from the inlet fitting and then down around the turbo behind the shroud so it looked like it was leaking from the outlet. Thanks for the info Newto and Geoff!

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