Yet another adventurous (read troublesome) trip...

[gumpy]

The fiber connector loose in the engine will not hurt it. I have spoken to many mechanics that have said "no big deal" if you accidentally loose it as you take out the compressor. They drop to the oil pan and just stay there. A bigger concern would be to have a compressor fail by lockup and wipe out the gears. Then you get to take your engine apart - No joy!

Yeah, I was wondering about that. At least with the fiber gear, if the compressor locks up, the gear will give. With the metal gear, it's a toss up whether the compressor will win, or the engine cam shaft. Either way, it can't be pretty, and could cost an engine.

[luvrbus]

Compressors have a safety key to prevent that from happening with the metal drive drive DD has not used the fiber drive since 1984 if you need something to worry about the gear driven alternator is a good one,fwiw never have I saw a fiber gear drive for a compressor on 92 series engine  


good luck

[bevans6]

Gumpy, what actually failed in your setup?  Did the compressor lock up and start things, or  did the fiber gear break up?  You mention that the compressor gear also broke - is that the metal female splined gear on the crankshaft of the compressor?

thanks, Brian

[gumpy]

Gumpy, what actually failed in your setup?  Did the compressor lock up and start things, or  did the fiber gear break up?  You mention that the compressor gear also broke - is that the metal female splined gear on the crankshaft of the compressor?

thanks, Brian

The fiber gear on the end of the compressor shaft failed.

Here's a photo...

[gumpy]

So here's the rest of the story... 

I replaced the compressor on the bus. Took the old one out and swapped fittings to the new one. Then spend a good amount of time plugging all the extra holes in the new compressor. There must be 15 dozen holes in that thing that are not used. All for different installations, I assume. Most of them had plugs that were hand tight in the holes, and I compared to old one to the new one to determine which ones got plugged and which ones didn't, and where the fittings went from the old own and even the orientation so the lines would mate up. Did I mention there must be 15 dozen holes!  I even had a helper who was being as diligent as I was about getting all the holes filled. I even told him a story of a fellow who bought a new compressor that had some of those red plastic plugs in the holes that had been painted over with black paint. He had missed one, and the plug had come out when he was driving, and dumped all his oil out and he lost his engine.

Well....  guess what?? 

Did I mention there must be 15 dozen holes in that thing?

I changed that thing and aired it up in the shop. No leaks. The compressor must have cycled 4 or 5 times as I backed it out and parked by the house. No leaks. We spent a couple more nights in it, and when we got ready to leave, I aired it up, turned around and pulled out on the snow covered driveway to hook up the car. No leaks. No leaks in the dirt. No leaks in the snow. No leaks.

We said our goodbyes and left. It's 2 miles to the interstate and the road was icy and the bus was not fully warmed up, so I didn't get over 25 mph or so. When I got to the interstate, I accelerated to 65. It's about 9 miles of interstate to Pueblo.  About 4 miles down the road, I noticed the oil pressure had dropped for 50 to about 30. As I watched, it kept dropping. I knew something was terribly wrong and was trying to get it to the exit to get off the interstate. Didn't make it. Decided to pull off the side when it fell below 25 psi. Just as I pulled to a stop, the low oil light and buzzer came on and the engine died (well, at least I know that sensor works!). I went back, knowing full well what I was going to find. Sure enough, there was black gold all over my transmission and running down both sides and onto the highway (and the toad).

I saw nothing obvious from the engine bay door, so opened the floor hatch. I immediately saw that there was a tiny little plug missing from the oil port on the bottom of the compressor. As near as I can figure, there must have been a plastic plug in that port that popped out when I finally got the engine up to highway speed and the oil pressure came up to 50 psi.

Maybe if the new compressor did not have the metal plugs in it I might not have missed this as I would have had to move all the plugs from the old one to the new one, but I guess I was so busy putting in the plugs that were already hand tight in the new compressor and moving fittings from the old compressor to the new one I somehow missed that little oil port. That little oil port dumped 3 gallons of my oil out in a matter of minutes!

I pulled the plug from the old compressor and put it in the hole in the new one and then put in 4 gallons of fresh oil (it was already down some before this happened). We found a truck wash a few miles down the road and cleaned off as much oil from the car and engine, creating a small environmental disaster which I'll blame on BP and Halliburton, and headed on down the road. My oil pressure even came up to 55-60 lbs for much of the trip home. Probably all that fresh oil in the system.

Fortunately, no harm done to the engine or compressor as I caught it in time, but this could have turned out very badly for me. 

I feel stupid about missing this plug, even after explaining it to my friend who was helping me, but the reality of it is, this stuff can happen no matter how careful we are. This is one prime example of why the safety shutdown system on these buses should be in proper working order. When my compressor failed, it became obvious that I was not paying as close attention to my gauges as I thought I was. If I had not been paying close attention to them this time, and the safety shutdown system was not functioning, I could very easily have lost my engine.

See, I am not good for nothing. I can be used as an example.

Learn from my mistakes.

craig

[Gary '79 5C]

Craig,

Glad this is corrected and behind you now. Excellent, informative write up, of which I am more knowledgable as to compressor failures.

Take away for me is 15 Dozen and one holes.

[Jriddle]

yep I am glade my safety system is working on my 9 also. I was watching my engine temperature raise last summer while I was trying to get pulled over and just as I came to a stop the engine shut itself down before any damage was done. I think it may have shutdown a little early but was glade to see it work.

John

[RickB]

I think that was my buddy Joe that you were thinking of...fresh rebuild, taking her on a shakedown cruise and he forgets one plug. He had to completely rebuild his motor again and he had put less than 5 miles on it. That's why we shouldn't jury rig our shutdown systems.
Glad you caught it Craig. You would've been one grouchy dude if you would have lost your motor.
Call me when you get home
Rick

[Barn Owl]

The fiber gear on mine looks nothing like the one on your bus. I didn't know there was a difference. Mine looks more like a small disk and has more in common with a love-joy coupling.

[bevans6]

I think that fiber gear is an MCI thing.  The compressor is unique to MCI, I think - the catalog shows it as an MCI configuration.  On mine, the gear is steel, probably fitted during maintenance.  The compressor is a 700, when a 600 was stock fitment. 

Gumpy, did the compressor lock up or fail to cause the gear to break up, or was it really the gear that failed?

Brian

[gumpy]

The gear failed, but I don't know why yet. I have not tried to determine if the compressor locked up or not. Will look at that when it warms up here and I
figure out if I can rebuild it for a spare or not.