New DD-3 mountedon my MCI 9, but having air problems?

johns4104s · January 31, 2010, 07:22:12 PM

Just finished mounting and connecting the new/rebuilt DD-3,s but my problem is the driver air pedal locks them down, releases them and then applies the brake correctly. There are no air leaks, but the driver brake pedal goes all the way to the floor board.
I have thought maybe we connected them up wrong but we plumbed them the same as the old one coming of.
Any experience or ideas?

thanks John

Dreamscape · January 31, 2010, 08:43:06 PM

John,

I read and re-read your post, I'm confused. You say the brake pedal when applied works fine, but then you say it goes all the way to the floor. What is your air pressure when apply the pedal? You should have some resistance when aired up. Does the pressure drop when you apply the breake pedal?

Paul

johns4104s · February 01, 2010, 05:25:40 AM

Paul,

I did not check the air pressure, it must be up there as the DD-3 will release. There is no air leaking when the the pedal is down
When I first got my 4104 the brake pedal would go all the way to the floor until I changed to a E-3 brake valve. Grey hound had them set from the factory that way so the drives would not not throw the passengers all over the bus.

John

luvrbus · February 01, 2010, 05:49:35 AM

John, that is a adjustment when you adjusted the brakes you turned the slack adjusters in the wrong direction common mistake set every thing on a 90 and start over.Make sure your stroke is right and go from there

good luck

johns4104s · February 01, 2010, 07:10:44 AM

Clifford,

So the way I have adjusted them with the arm of the slack adjuster pushing towards the brake can is wrong?
The correct way is it should be pulling away from the brake can until the wheel is locked then back off a 1/2 a round, Correct?

Dreamscape · February 01, 2010, 08:38:08 PM

Have you figured out what was going on?

buswarrior · February 01, 2010, 08:46:59 PM

oh dear.... keep typing, we'll get to the bottom of this.

Did you take this opportunity to put in a fresh inversion valve?

happy coaching!
buswarrior

johns4104s · February 02, 2010, 04:23:38 AM

BW, An inversion what?

Were and how do you put one of these in and why does it need it

thanks

John

Nellie Wilson · February 02, 2010, 05:11:00 AM

Quote from: johns4104s on February 02, 2010, 04:23:38 AM
BW, An inversion what?

Were and how do you put one of these in and why does it need it

thanks

John

John, jump over to topic "Re: Thread Drift ~ How Far Can It Go?" I'm pretty sure somebody explained it over there... though I'm not really sure.

Nellie

Dreamscape · February 02, 2010, 07:55:23 AM

If the inversion valve worked before replacing the DD-3's, is should work now. It has to be in the re-assembly somewhere. I'm sure John will find the problem, fix it and get back to us.

Paul

buswarrior · February 02, 2010, 06:31:08 PM

Yes, as Paul says, find what's wrong with what you already touched before you go messing with anything else.

Once that is sorted out...

The inversion valve is that little beast mounted above the differential that has 4 of the 6 lines from the DD3 chambers routed to it. The parking control valve beside the driver is the 5th line attached to it. The dedicated parking air tank is the 6th line. And it has its own exhaust.

It is key to the proper functionality of the parking system.

More than likely it has not been replaced in a long enough time in its previous life that a busnut will want to change it out as good preventive maintenance, and then it is done.

Fresh chambers, fresh air lines, a fresh relay valve and a fresh inversion valve puts the entire rear brake system to bed, for many years to come.

Let us know how your symptoms are coming along.

happy coaching!
buswarrior

Cary and Don · February 02, 2010, 07:34:00 PM

On knowing which way to turn the slack adjusters, I was told that first you turn them the easy direction and then ratchet them back the 1/4 turn. There is a difference in the resistance on the two directions. You can also see the brakes move back away from the drums.

Don and Cary
GMC4107
Neoplan AN340

Dreamscape · February 02, 2010, 08:08:38 PM

By tapping on the drums you can tell when the slacks are adjusted. A slight ring is not tight enough, a dull thud is good, then back it off 1/4 turn. That is what has worked for me.

Paul

bevans6 · February 03, 2010, 05:36:20 AM

And then measure the stroke when the brakes are fully applied at a pressure between 90 and 100 PSI. That's the test, not "back off 1/4 turn".

Who knows what the limit is for a type 30 spring brake, a type 24 can, and a type 30 DD3? Who knows why you use between 90 and 100 psi? Who knows what "free stroke" is, and why it isn't a valid measurement of brake adjustment?

http://www.cvsa.org/programs/documents/air_brakes/Air%20Brake%20Adjustment%20Brochure.pdf

Brian