oil leak on gear drive altenator

artglass · February 27, 2007, 07:19:18 PM

Got oil seaping out of the two screws on passenger side of stator on altenator is ona Mc8 with the gear drive unit, no one at mci can even find the screws in the book , was wondering if any one has ever had oil leak the seat is a little bit recessed into th eoutside of the stator, not sure if there should be a gasket or oil on the screws seem to be about 1/4" self tapping screws in them. Any ifo would be greatly appreciated.

TomC · February 27, 2007, 10:38:11 PM

The big Delco DN50 gear drive alternators are sealed, pressure oil lubricated and cooled by the oil, brushless design. If anything is leaking, needs to be resealed. Look at the alternator. The engine oil feed from the engine goes to the back of the alternator. If it is an updated version should also have a small oil line going to the engine block side of the alternator to that bearing. If you don't have that extra oil line, maybe consider just getting it overhauled, or exchange for an updated version. Good Luck, TomC

Sammy · February 28, 2007, 05:58:56 PM

They are 1/4 inch self tapping screws. There are 2 large o-ring seals, one on each end of the stator.
The stator (center piece of alternator) has a machined groove for this o-ring to sit in at each end.
I would try to tighten all the bolts a bit, being careful of course. Do it by hand, no air tools.
I have rebuilt many gear and belt driven 50 DN units.
Good luck with your repair.
Sammy

H3Jim · February 28, 2007, 09:34:42 PM

what is the story on the oil lines to the alternator. The service manager at Prevost said he thought it was just a larger return line, and saw no value in making the modification. Both you Sammy and Tom C are in a position to know and are great resources. Thanks in advance for any comments.

TomC · February 28, 2007, 11:39:07 PM

On the original design of the 50DN, the pressure oil from the engine came in at the rear of the alternator (furthest away from the engine), first lubricated the end bearing then flowed through the alternator cooling it with the splashing of the oil reaching up to the front bearing. They discovered that the front bearing was prematurely failing because of limited oil getting to it through the splash effect. The remedy was to first enlarge the bearings, then drill the front bearing to get pressurized oil straight from the engine, along with a new design on the stator. While the oil going through the alternator is flowing at something like 2 gallons a minute, the front bearing has a restrictor on it so it is just getting a dribble. Course a big ball bearing doesn't take alot of oil flow to keep it happy. Now you know what that oil line to the back of the alternator is for. Good Luck, TomC

H3Jim · March 01, 2007, 07:17:02 AM

So how can I tell if my 1995 coach has the newer or older style 50 DN? Mine is a belt drive.

Should I apologize for hijacking this thread?

TomC · March 01, 2007, 08:06:56 AM

Typically the belt drive 50DN's are the upgraded version with two oil lines on the top of the alternator and the large return line on the bottom of the alternator. When it goes out you might consider going to a VLF series of Prestolite which is a 300 amp at 24 volts or 325 amps at 12 volts. The advantage is that it is air cooled, so no oil lines; the cooling air can be plumbed into an air cleaner (for military use mostly). It has brushes that are long life, where the 50DN has none. Main advantage is you get rid of the oil lines with the VLF. Go to www.prestolite.com Good Luck, TomC

Sammy · March 01, 2007, 01:49:16 PM

Gents, check out this link: http://www.detroitdiesel.com/public/sibs/sibs/14-60-00a.pdf
See page 15 in the file. A little more info for everyone. Tom, thanks for the Prestolite info, will look into it a bit more.
Sammy

muddog16 · March 02, 2007, 05:36:14 AM

Hey Tom was the Prestolite price the same as a DN50?

Pat

belfert · March 02, 2007, 06:11:15 AM

Isn't the whole reason for an oil cooled alternator to get better cooling for the alternator? Will an air cooled alternator that is 300 amps really stay cool?

If a DN50 was removed, could the oil ports on the engine be plugged or would a line need to be run from the output ports to the intake port?

Brian Elfert

Busted Knuckle · March 02, 2007, 07:26:18 AM

Quote from: belfert on March 02, 2007, 06:11:15 AM
Isn't the whole reason for an oil cooled alternator to get better cooling for the alternator? Will an air cooled alternator that is 300 amps really stay cool?
If a DN50 was removed, could the oil ports on the engine be plugged or would a line need to be run from the output ports to the intake port?
Brian Elfert

Brian,
Yes the air cooled altenators are very efficient in cooling, and it eliminates the possible oil leak/ broken oil line scenario ! 1 less headache to worry about! But if it were me, I wouldn't go chang'n just to change it. If it ain't broke, don't fix it! Now on the other hand if ya ever do need to replace it I'd step up to the Prestolite as reccomended by Tom! FWIW. BK