bus wont build air pressure

[chessie4905]

Compressor has a drive cup on end. Remove bolts ant just take it off.

[chessie4905]

The cup gear attached to compressor is made of fiber bonded to steel core where it attaches to compressor. Normal failure is the fiber teeth strip off or the cup comes loose from steel core that bolts to compressor. Made of fiber so if fails, the fiber parts can go through engine gear train without gear damage. Easy to reinstall compressor. Just engage cup with sleeve gear teeth. That spring is there to stop in and out play of compressor crank attached to cup.

[luvrbus]

The cup gear attached to compressor is made of fiber bonded to steel core where it attaches to compressor. Normal failure is the fiber teeth strip off or the cup comes loose from steel core that bolts to compressor. Made of fiber so if fails, the fiber parts can go through engine gear train without gear damage. Easy to reinstall compressor. Just engage cup with sleeve gear teeth. That spring is there to stop in and out play of compressor crank attached to cup.

His drive will probably be the more up to date drive,I haven't saw that drive in years John 

[dtcerrato]

 Pictured is the same compressor drive as we have - in failed, run, and have as a spare. Chessie's description is a good one.

[luvrbus]

Pictured is the same compressor drive as we have - in failed, run, and have as a spare. Chessie's description is a good one.

Those were prone for failure John is right ,the same drive that failed John Z on his 4104 in Texas Sonnie and Mike changed over to the newer drive in freezing weather

[goutoe]

Thanks guys, My compressor is A BW if that helps? I did change out the air Governor as well, looks like a fairly simple job as mine is a V drive hopefully tomorrow  I will have time to get the compressor pulled and have a look.

[dtcerrato]

IMHO it's not like the old style fiber gear was problematic!
Heck in 43 years of same bus/engine ownership the compressor drive failed twice. The 1st replacement was brand new the current replacement (6 years now) is a part from an older bus and the spare part I carry is from an old bus. I'm okay with that. Purely mechanical & nothing catastrophic...over approaching a half a century! 

[chessie4905]

When ours failed on the 4104, switched over to steel gear. Course if IT fails, major damage. Never had an issue though.

[luvrbus]

Detroit was always good when a problem area was causing problems to update to a better system or parts ,I still come across old DD the upgrades were never made,then they are not out beating the pavement for 100,000 miles a year either.Doyle installed a rebuilt blower on his 8v71 I told him he needed to update the blower drive naw he said it has worked fine since the 70's 4 days later I sent him the blower drive an parts he was broke down in Arkansas   

[goutoe]

After a thorough power washing I found an ID tag Bendix  tho- 700 cant read the other nos. till I get the compressor off. Thanks for The pics and description Chessie that helps me understand what I'm looking at , I really appreciate that. John.

[fortyniner]

The biggest pain removing my compressor aside from its weight was plugging coolant lines quickly to avoid a mess.  I believe the drive coupler in mine was all metal but its been a while since I had it off.

[dtcerrato]

The biggest pain removing my compressor aside from its weight was plugging coolant lines quickly to avoid a mess.  I believe the drive coupler in mine was all metal but its been a while since I had it off.

When we're doing work that requires disconnecting coolant lines we lower the coolant by draining some of it off - a few to five gallons gallons should get it below the compressor.
The compressor drive coupler could be all metal - ours is but the female driven coupler (gear) on the compressor could be all metal or a combination of metal gear teeth with a fiber hub that could fail by "slipping" at above low PSI - it'll fool you unless you test it by locking the compressor from turning and putting a large channel lock on the "coupling" and try turning over the compressor - if you can with the compressor crank locked up - it's slipping but only under a load. We had one do that and it drove us crazy trying to figure - almost replaced the compressor but when we realized the driven gear was slipping we replaced it with an even older one - it's been 6 years in service w/o issue!

[goutoe]

Dan thanks for the info, I wondered why it would build some air? I have the coolant drained down, and everything washed off, now just need the time to work on it. good thing is I dont need to use the bus till mid May! I am concerned about parts availability? John.

[chessie4905]

Luke's got them. And gaskets or whatever else

[goutoe]

Chessie, I have seen posts referring to Luke But I don't know how to contact him do you have his info?? Thanks. John.