DD 6-71 massive oil leak.

[LesBerg]

So what the hell is this part (circled in red) and why am I dumping a gallon of oil out running for a half hour?


This isn't my motor, but I can't track down what this is. It's not in the manual, and I'm not finding it in parts diagrams.

[Dr_Detroit]

Looks like the crankcase vent assy. If you are losing lots of oil through it check the oil level and make sure it is not overfilled and causing it to be whipped by the crank. You can't always depend on the dip stick to be correct. If it is not overfilled, then something is pressuring the crankcase causing it to force the oil out. Possible hole in piston, broken compression rings etc.
I have seen a restricted exhaust cause this also. Good Luck, Donnie.

[LesBerg]

Thanks. That's what I was hoping to hear. Unfortunately, I'm fairly sure that the dipstick is accurate. When the oil level drops off the bottom, pressure drops to about 2lbs at idle.

I can verify, though, by doing a needed oil change and adding the proper amount to the crankcase. We've only had our 4104 since May or so, and it hasn't left the yard since we got it home.

The oil leak is only one of several problems. It also has a thoroughly frozen throttle cable and the rear brake cans do not move with air applied to either the spring brake valve or the treadle.

All the weather stripping needs to be replaced, the AC units are shot, there are four cracked side windows - including one with a bullet hole, which to me appears to be a .45 fired from the inside.

There are numerous electrical bubba-fixes that need to be properly sorted out, etc.

Once we've got it closer to road-ready, I'll adjust the injectors, run the rack, and adjust the governor.

[gomer]

this picture to my thinking is a marine engine.  I have a 57 4104 and it doesn't look like this at all.  My exhaust is on the others side and the blower is where the exhaust is on your picture.  Just a thought from me

[LesBerg]

Yeah. This isn't the motor in question. Mine has the circled bit and this was the only picture I could find of a DD6-71 that has it.

As an update, I have found the source of the problem. The motor in our bus uses the one-piece exhaust manifold and stacked mufflers. The slobber hose drains on top of the driver side front engine cradle mount and runs right past the end of the manifold.

I could only come up with two ways we could be losing that much oil out of the slobber hose:
1. horrifically bad blower gaskets
2. leaking air through the engine shutoff solenoid on the back end of the block.

Well, I'm pretty sure our blower gaskets aren't leaking, or at least not to that extent. The air-powered shutoff solenoid leaks, but again, I don't think it's that bad.

I was underneath it on Sunday working on the throttle cable, and decided to have another look. I found a 3/8 inch plastic air line routed where it could rub against the edge of the lower muffler, and sure enough there was a hole in it where it was touching the muffler.

I traced the line back to it's origin on the motor.... It's a supply line for a mechanical oil pressure gauge mounted in the dash. A P.O. attached it next to another mechanical oil pressure gauge in the engine compartment and ran the 3/8 line all the to the dash. There are probably six more places in the line in severe danger of chafing through the plastic where the line passes through a hole drilled in a bulkhead without benefit of a grommet.

Next weekend I'll disconnect it in the engine compartment and remove the line. I'll be putting in an electric gauge in it's place.

[gusc]

I always ran my 671 around a gallon below the full mark, otherwise it would just throw it out.

This holds true for most engines I've ever owned. My airplane would throw out the top two quarts in 5 min then not burn any more for hours.

[Brandon]

Next weekend I'll disconnect it in the engine compartment and remove the line. I'll be putting in an electric gauge in it's place.

Even my positive ground 1955 TDH-4512 had an electric oil pressure gauge from the factory.

Still has one now...nice short flex-line to the firewall manifold with low risk of failure!

[LesBerg]

At the moment, I have just a drop showing on the bottom of the dipstick and almost zero pressure at idle. I saw that the pressure wasn't coming up after about 15 seconds and shut it down.

This could be that the hole in the feed line is causing an inaccurate low reading on the dash gauge, but the gauge on the motor shows low too. Again, this could be because of the hole in the line. I'm cautious about it though - when the dipstick shows 'Full', I get about 15psi at warm idle even with the leak.

Regardless, I'm going to disconnect the feed line for the dash gauge, plug it, and install an electric gauge.

Thanks for the assistance, everyone!

[pd41044039]

You are definitely losing some from that line leak.  But IF your mechanical gauge is accurate, 15 lbs at idle (these idle at about 450RPM is pretty normal.  50 at speed is typical (when warm).  You should be using a straight 40 eight 2 cycle Diesel oil.  Don't let them con you into multi grade or synthetic.  (you get oil consumption problems).
The correct oil level should be about 1" below the oil pan / block seam.  You can measure this with a broom straw first thing in the morning before starting.
The cylinder thing is a crankcase vent.  Mine has it too.
Also, you won't be able to judge engine condition, smoking, consumption properly until you get it road worthy & drive it at least an hour.  It will still be waking up until then.

[LesBerg]

Excellent information, thanks. Would you believe that I can actually get Delo 100 from O'Reilly auto parts up here?

http://www.oreillyauto.com/site/c/detail/CHV1/100401/N0422.oap?ck=Search_N0422_CHV_CHV1_-1_3771&mn=Chevron&mc=CHV&bn=Delo&bc=CHV1&pt=N0422&ppt=C0162

I'll post pressure numbers once I get the line capped. I think I even have a spare electric pressure gauge kicking around here somewhere.

Also on the list before too much driving is a full rack adjustment and set the governor.

gotta go! time to pack out for the drive home!

Thanks,
Les

[zimtok]

My 4104 has a mechanical gauge in the engine compartment on the drivers side fire wall just above the engine.
That is also where the electrical pressure switch is located for the gauge on the dash.


.

[LesBerg]

Good to know. Mine has a mechanical gauge mounted just above the oil cooler next to the driver side cradle support. There's a sending unit for an electric gauge there too, but I'll have to test it.


Off to get parts!

[LesBerg]

Yeah, that line was my entire leak. I pulled the fitting and plugged it with a 1/8npt plug and added a gallon of 40wt.

Initial idle oil pressure was 55psi. It dropped to 18 as everything warmed up. I ran it for about 40 minutes and no leaking.

Got the air governor adjusted while I was at it. It shuts down at 105 and comes back on around 82 or so.

[eagle19952]

Yeah, that line was my entire leak. I pulled the fitting and plugged it with a 1/8npt plug and added a gallon of 40wt.

Initial idle oil pressure was 55psi. It dropped to 18 as everything warmed up. I ran it for about 40 minutes and no leaking.

Got the air governor adjusted while I was at it. It shuts down at 105 and comes back on around 82 or so.

I have been wrong before, but 105 seems 15 psi too low ?

[luvrbus]

105 psi on a 4104 is about right I had a hard time with that also Donald even reading it in the manual