GM 4108 Air Leak

[luvrbus]

I thought there was a clearance problem putting them on the 4108?

There is with some models of spring brake but you buy the spring brakes with the rotatable chambers and they clear,MGM was supposed to start manufacturing a direct replacement for the DD3 before the CV-19 hit 

[chessie4905]

currently, none will work on 4107, 8, 4903 and on up. Not enough room without body clearancing. Even if they would fit, the caging bolt would hit the bulkhead. Also the plumbing would require some significant rework that would be beyond the general owner or shop.

[luvrbus]

I installed spring cans on River Bill's 4905A 6 years ago the cage bolt is a simple deal and the plumbing is just reversing the air supply with 2 lines from the brake relay just like you do on a 4106,The MaxiBrake spring brakes from a older R600 Mack Truck are easier if you can find a set 

[richard5933]

Final chapter of the saga...

The original problem was a failed tank drain which I had the shop install about three years ago. This is on the rear tank which is mounted above the rear axle and not accessible at all without getting under the bus. They installed the drain with a pull cable. Worked great until last week.

They replaced the drain valve, and then went on to replace the diaphragms in all four brake cans since they were leaking as well. Everything was great and the bus held air all weekend. Then I picked it up this morning and drove it home. Then that new drain valve proceeded to leak even worse than the first one.

Took it back. Apparently the tank drains being made in China have a sketchy track record. New valve installed, and it appears to be good for now.

Question...

With that tank being above the rear axle, was it ever intended to be drained daily? No way to get to it without a pit, and I seriously doubt that these buses were all put on a pit daily. Am I to assume that this tank was not intended to be drained other than when in for service?

The rest of the repairs (diaphragms, etc.) went without a hitch. The original diaphragms are actually in good shape and could probably have been reused. The problem with the brake cans was solely due to corrosion on the mating surfaces of the cans forming leaks where the diaphragm mounted. New diaphragms were installed for good measure though, after the cans were given the once over and had the mounting surfaces cleaned.

[Ed Hackenbruch]

My bus came with a rebar T handle that the PO made for reaching in to drain the tanks. It worked but i never cared for it so put cable pull drains on all of them.

[sledhead]

I replaced all my pull drains and installed small 4"-6" pull cable loops that I can get at with the old awning rod . even the drain between the drive tires if I reach through the tag and drive opening . works every time . so yes I can drain all the drains from standing beside the coach with the help of the awning pull rod . no squashed bus nut to drain the tanks

dave

[chessie4905]

I'm surprised you haven't installed an air drier yet.

[richard5933]

No air dryer yet. Not sure when. I asked at the shop today when I picked up the bus and the answer was pretty much there was no immediate need unless I was going to start traveling more in freezing weather. Otherwise just keep draining daily.

All my tanks have accessible drains except this one over the rear axle. That's why I had them put the pull-cable on it so I can drain it safely.

Still confused as to what the plan would have been for this bus in revenue service. Clearly they didn't intend for every bus to be put over a pit every day to drain this tank, so how/when was it drained?

[buswarrior]

The wet will be in the wet tank, the rest should be dry.

First tank after the compressor.

I doubt you get anything out of the rest?

Happy coaching!
Buswarrior

[richard5933]

The wet will be in the wet tank, the rest should be dry.

First tank after the compressor.

I doubt you get anything out of the rest?

Happy coaching!
Buswarrior

Thanks - that's been my experience so far.