Author Topic: Failed DD3?  (Read 2135 times)

Offline Stormcloud

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Failed DD3?
« on: March 10, 2018, 06:33:08 AM »
OK, guys.   Air holds fine when parking brakes applied.  Plunger in to release parking brake, and air is dumping at the back by tag axle.
Could be relay valve, could be bad DD3. or line line, or .......

Compressor barely keep up with air loss at higher RPM.

A suggestion was made to disconnect the bad DD3 to make bus driveable to get parked in an RV park, and get parts ordered.
If so, do all 3 lines have to be plugged at the can? or just 1? 

Stuck here for a few days.  :(

Thanks.
Mark



Mark Morgan  
1972 MCI-7 'Papabus'
8v71N MT654 Automatic
Brandon, Manitoba, Canada in summer
somewhere near Yuma, Arizona in winter(but not 2020)

Offline thomasinnv

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Re: Re: Failed DD3?
« Reply #1 on: March 10, 2018, 06:51:09 AM »
OK, guys.   Air holds fine when parking brakes applied.  Plunger in to release parking brake, and air is dumping at the back by tag axle.
Could be relay valve, could be bad DD3. or line line, or .......

Compressor barely keep up with air loss at higher RPM.

A suggestion was made to disconnect the bad DD3 to make bus driveable to get parked in an RV park, and get parts ordered.
If so, do all 3 lines have to be plugged at the can? or just 1? 

Stuck here for a few days.  :(

Thanks.
Mark
First thing you need to do is try to determine exactly where the air is coming from. Is it coming from the relay valve? Inversion valve? That would help to narrow down the possibilities and tell you where to start investigating. Might not be the dd3 at all. More than one component comes into play just at the push or pull of the park brake brake valve.

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Some are called, some are sent, some just got up and went.

1998 MCI 102-DL3
Series 60 12.7/Alison B500
95% converted (they're never really done, are they?)

Offline Stormcloud

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Re: Failed DD3?
« Reply #2 on: March 10, 2018, 06:58:11 AM »
Always think the worse, but hope for the best.  Likely one of the thinnest mechanics I have ever seen came out, and slid under the bus to track the air leak. ( Yes, I blocked the body up first.)

Two air lines to DD3 rubbing together, one was worn through causing the leak.

He is sourcing a replacement hose or, at minimum, splice kits.
Mark Morgan  
1972 MCI-7 'Papabus'
8v71N MT654 Automatic
Brandon, Manitoba, Canada in summer
somewhere near Yuma, Arizona in winter(but not 2020)

Offline chessie4905

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Re: Failed DD3?
« Reply #3 on: March 10, 2018, 07:56:57 AM »
If it is the hoses connecting to dd3, common on trucks too. Take old ones to truck supply or big truck stop or NAPA.
GMC h8h 649#028 (4905)
Pennsylvania-central

Offline luvrbus

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Re: Failed DD3?
« Reply #4 on: March 10, 2018, 07:59:20 AM »
Always think the worse, but hope for the best.  Likely one of the thinnest mechanics I have ever seen came out, and slid under the bus to track the air leak. ( Yes, I blocked the body up first.)

Two air lines to DD3 rubbing together, one was worn through causing the leak.

He is sourcing a replacement hose or, at minimum, splice kits.


Lol I just repaired a Eagle 1 line was bad on the supply to the DD-3 he thought the worse too 8 bucks, it wouldn't have been that much but I replaced the DOT tubing with a rubber hose to get more flex
Life is short drink the good wine first

Offline Paso One

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Re: Failed DD3?
« Reply #5 on: March 10, 2018, 08:51:50 AM »
Glad to hear you had a nice and easy repair. :)
68 5303 Fishbowl 40'x102" 6V92 V730 PS, Air shift  4:10 rear axle. ( all added )
1973 MC-5B 8V71 4 speed manual
1970 MC-5A  8V71 4 speed manual
1988 MCI 102 A3 8V92T  4 speed manual (mechanical)
1996 MCI 102 D3 C10  Cat engine 7 speed manual  (destined to be a tiny home )

 

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