GM 4108 Air Leak

[richard5933]

Sounds like I might have escaped major problems this time... They're thinking it was just a faulty tank drain check valve.

Will know more tomorrow.

[Handyjim]

Great!!  More money to spend on other things  :

[chessie4905]

Funny, I had a pull cord one on the 4104. It developed a pinhole through the ball. Had to be a mfg defect.
Glad you got lucky...this time🤫

[richard5933]

Even funnier is I only had this drain valve replaced three years ago when I got the bus. Guess not even new parts are any guarantee against issues like this.

They're going to give the entire system a close look tomorrow to make sure that the tank drain leak isn't masking another problem. Hopefully this is all there is.

[richard5933]

Further update...

Back of the bus appears to be holding with just the tank drain valve being replaced. No problems with the DD3 chambers. However, I wasn't crazy when I said I thought I heard something up front with service brake application. Both front chambers are leaking. The fun never stops. The shop is working with Luke right now to get the parts to them.

[richard5933]

The maintenance manual indicates that the front diaphragms should be replaced at 100,000 miles or annually. No reference made of a schedule for replacing diaphragms in the DD3 chambers. Not sure if it's wise to service the rears right now as a precaution or to wait. Either way, I'm going to have Luke send the parts so they'll be on hand whenever necessary.

Also, when the tech initially reported the need for front chambers/diaphragms, he made a comment that one of the front chambers had two air lines going to it. Luke is not sure what he means? I'll have to drive up there this afternoon to see for myself.

Anyone know of a GM front chamber that has two airlines? I'm thinking he's seeing another air line in the vicinity, not one going directly to the chamber. Always something, isn't it?

Edit...

Apparently both front chambers are the same. Must have been a communications mix up or something.

[richard5933]

Glad I had the forethought to have Luke send all the diaphragms, not just the front. After the front were done and sat overnight, the shop called to let me know there is a leak in one of the rear diaphragms. Now they're going to be changed out and hopefully I'll be good to go for another few years, at least. Will feel much better knowing that the diaphragms are all new and (hopefully) up to the task at hand.

Also glad I've got a shop that I trust to do the work and that's actually willing to break open a brake can and replace the diaphragms.

[luvrbus]

Spring brakes are the only chambers that can hurt you,that spring can bite you big time 

[richard5933]

Spring brakes are the only chambers that can hurt you,that spring can bite you big time

Guess I was thinking more about shops that are into just replacing parts nowadays instead of rebuilding things, whether from lack of skilled techs or liability issues. Jack has been working on buses for 40+ years from what I've heard, so I'm sure this is not the first set of DD3 cans he's ever opened. May have been a few days since the last one though.

[luvrbus]

Guess I was thinking more about shops that are into just replacing parts nowadays instead of rebuilding things, whether from lack of skilled techs or liability issues. Jack has been working on buses for 40+ years from what I've heard, so I'm sure this is not the first set of DD3 cans he's ever opened. May have been a few days since the last one though.

He probably has open a few DD3 chambers in his life lol I was throwing out some old paper work and seen a bill for a set of diaphragms for the DD3's the set (2) cost less than 6 bucks in 1983 times have sure changed since Bendix dropped support of the DD3's ,if they ever do need replacing you can install spring brakes on the 4107 and 4108 MCI guys are not that lucky   

[windtrader]

Guess I was thinking more about shops that are into just replacing parts nowadays instead of rebuilding things, whether from lack of skilled techs or liability issues.

OR cheaper to swap parts. #1 reason

[luvrbus]

OR cheaper to swap parts. #1 reason

>
 
So true it adds up at over a $100.00 per hour shop rate to rebuild parts 

[richard5933]

DD3 cans are not cheap, so even an hour or so each is still cheaper. I've had some things rebuilt over the years that would have been cheaper to replace just because the OEM parts were better than the current production replacements.

[luvrbus]

DD3 cans are not cheap, so even an hour or so each is still cheaper. I've had some things rebuilt over the years that would have been cheaper to replace just because the OEM parts were better than the current production replacements.

Only new DD3 chambers you can buy now are aftermarket made who knows where for 600 bucks ea,spring brakes are around 100 bucks ea  and all truck stop carry them 

[richard5933]

He probably has open a few DD3 chambers in his life lol I was throwing out some old paper work and seen a bill for a set of diaphragms for the DD3's the set (2) cost less than 6 bucks in 1983 times have sure changed since Bendix dropped support of the DD3's ,if they ever do need replacing you can install spring brakes on the 4107 and 4108 MCI guys are not that lucky

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