50dn alternator issue.

TheHollands! · June 05, 2019, 08:37:18 AM

Hi all,
I have a 50dn oil cooled alternator in my MCI-9. Iv'e recently noticed that when I'm pulling an incline from a stop and the engine is really under strain, that I have some oil spraying up onto the roof of the engine bay from what seems like the alternator. I can't figure out where exactly it's spraying from, I wish I could visualize it as its happening so as to know what I need to replace. It doesn't seem to do it when just running down the highway. I know its all a bit vague, is there a logical point this might be happening. The alternator seems to be charging fine, wondering if its best just to have it changed out, or would a shop be able to stage the situation and identify the leak better and maybe just need to replace a few parts. I feel like I'm talking myself through this but wanted any advice from you all. Thanks, Craig

bevans6 · June 05, 2019, 09:03:11 AM

MC-9 gear driven alt drains and vents to the gear drive housing, so it's internals are basically identical in pressure to the inside of the gear drive housing, which is to say atmosphere but vented to the crankcase. If the engine is working very hard, you could have a lot of blow-by pressurizing the crankcase, hence the gear drive housing hence the alternator, but that is a bit of a stretch. Might just be a bad gasket, after all. Not only is the engine working hard in such conditions, it is probably running at higher rpm than normal, running up to governed limit in lower gears, etc, and oil flung off of gears can get everywhere.

Utahclaimjumper · June 05, 2019, 09:05:03 AM

It sounds like you want to just throw parts at it until the problem goes away,,start by tightening various end cap bolts,,mounting bolts ,, check gaskets,, oil fittings and lines and items around the problem area like maybe an oil manifold in the area and that sort of thing.>>>Dan

TheHollands! · June 05, 2019, 09:44:20 PM

Thanks for the input, I'll start by tightening everything and looking it over close once I get parked in the next couple of days. I'd love to mount a camera back there to see whats going on. I may try rig something up. Craig

chessie4905 · June 06, 2019, 03:25:15 AM

If it has that little oil line, maybe it's leaking, or the oil line.

richard5933 · June 06, 2019, 05:55:43 AM

This might sound oddball, but could a worn-out engine mount(s) be causing this?

My thinking is that when under heavy load the engine is more likely to want to move, and if you have a hairline crack or lose oil line somewhere that movement may open the leak enough to cause it to shoot all over the place.

Geoff · June 06, 2019, 01:22:14 PM

The oil could be coming from the oil feed line to the blower.

TheHollands! · June 08, 2019, 01:08:32 PM

I have an update for you all. Iv'e found that the oil is actually transmission oil squirting out of the dipstick tube on shutdown, maybe other times too. It ends up landing on the alternator, hence why I thought it originated around there. Would this be simply needing to replace the dipstick to get a better seal, or is this a bigger problem? Thanks for all your ideas. Craig

neoneddy · June 17, 2019, 12:11:17 PM

Also check the fan miter box fluid level. I had oil spray right above and on my alternator for a while. The vent / overflow for that spray oil into the fans, the fan whip the oil down and back. Took me almost a year to figure that out, all the while thinking my dark sight glass meant the level was low, doh!

Hop up there and see if the vent is clean and shiny like it's been wet from oil.

TheHollands! · June 18, 2019, 07:10:11 AM

Hi Neoneddy,
Thanks for the idea, I'll take a look just to make sure. I did find the main culprit was a bad transmission dipstick that was spraying oil on shutdown. Iv'e found owning this bus has been real fun trying to learn and trace all the different systems and odd things that can go wrong. Overall, Iv'e been amazed at how reliable these old buses are, at least mine has been quite terrific over the years in what it has enabled us to do. For a cheap platform to convert out a home that we've been able to travel in for 8 years, the repair costs can be a little hefty but not ridiculous considering all the moving parts and the hauling these things do. Big thanks to all on those on these boards that help problem solve the mishaps. Thanks, Craig

Oonrahnjay · June 18, 2019, 09:06:14 AM

Quote from: TheHollands! on June 18, 2019, 07:10:11 AM... I did find the main culprit was a bad transmission dipstick that was spraying oil on shutdown.
.... Big thanks to all on those on these boards that help problem solve the mishaps. Thanks, Craig

Glad you got there, Craig. Wishing you many good miles; thanks for sharing the info and appreciation.