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2007 brakes
#1

winegrower was here with his 2007 4 slide steerable tag beautiful coach.  we spent some time working and learning on it.  i still no not claim to be any kind of an expert so take all of this as what i understand but may be not totally accurate.  

for a few days, we thought we had a brake problem that ended up not being one.  

i might add, that what we learned is that the system is a tad different then the one on my 2002.

his coach has both both abs and traction control.  

the problem we thought we had was found when we were working on the leveling system and supply air leaks.  

if you recall, as long as your check valves and ppv valve is working properly both your front and rear brakes should stay pressurized when you are sitting without touching the brakes for days. (on my 02).   if they both go down with the supply air pressure, then you have  bad check valve.  

that is the premise i was operating on for bobs 07.  i called richard and steve to confirm and discuss.   the problem we were having is when we would discharge air from the fill port in the rear passenger side engine compartment (we use shop air when in my shop), then several things happened that i couldnt explain.   first the supply air stayed pressurized to 60 or so and the front brakes went to ZERO and the rear brakes would go down to 75.  that is all from 125psi or so.  

in the older coaches, that would mean the ppv valve is malfunctioning and there are other threads about where to find it on the frame rail in the rear horizontal frame.  well, we looked and looked and could not find a ppv valve.  and still wondered why the supply air would stay up at 60 or so and not go down when we drained the supply (labeled accessory tank) on bobs.  

the supply pressure was easily explained.  in my 02, there is a 12v system for the potties, air door, and pocket doors.   it has its own little tank in the passenger side drive wheelwell.  and is kept isolated from the 120v and engine compressor by a check valve that allows air to come into the 12v air system but not back out.  and that is kept at 60 or below.  when i asked newell, they said there was no additional tank up front.  so that meant there was a check valve somewhere for the doors on the 07.   never found it but likely in the air things we found in a bay to the rear of the entrance door.  but at least understood

but why was the front brakes going to zero, rear staying up and why couldnt we find a ppv valve?

i ended up finding this video on youtube made by bendix.  

https://youtu.be/Mdtfly3-ogo             yes it is a safe link

when looking at all the valves and tanks on bobs 07, it matched this video.  

in the rear there is a front brake tank (secondary), a rear brake tank (primary), a brake relay valve (r14), and a front and rear abs valve (those three valves shown in the picture and were on the aft side of a horizontal frame rail above the drive wheels) a spring brake modulating valve on the back frame rail horizontally by the tags.  in addition, there was a very different looking air dryer in the drivers side tag wheel well.  the one on my 02 looks simple with a filter on it.  the one in bobs had way more on it and an air chamber as well.  ends up it is a Bendix® AD-IS®. and that is why we couldnt find the ppv valve separately.  it has the ppv valve built in it.  

i called bendix tech support (which is incredibly helpful) and they explained that the way that air dryer operates is that it will allow the front brakes to go to zero when the supply air is drained and the primary (rear) to stay up.  so it was operating the way it was supposed to.  btw,  call them about anything bendix related and they are super smart and helpful

btw, when sitting overnight or longer, with the shop air off and all tanks just topped off, the brakes will settle down to 75 and stay there.

so, the video above is exactly the setup that is on bobs 07 as i understand it.  

the only additional things are the traction control valves for each rear suspension that is fed by a 1/4 inch control line coming from some bendix controller that i assume comes into play somehow.   here is what i got from an bendix document

"controller provide an Automatic Traction Control (ATC) feature. Bendix ATC can improve vehicle traction during acceleration, and lateral stability while driving through curves. ATC utilizes Engine Torque Limiting (ETL) where the ECU communicates with the engine’s controller and/or Differential Braking (DB) where individual wheel brake applications are used to improve vehicle traction. Premium EC-60™ controllers have a drag torque control feature which reduces driven-axle wheel slip (due to driveline inertia) by communicating with the engine’s controller and increasing the engine torque."

so i dunno if the 07 has all of that or not, but something to research.

also, remember that the parking brake modulating valve keeps the parking brake (controlled by mechanical springs) off when there is high enough air pressure in the brakes (bobs seems to come on between 50 and 60 when we discharged the brake tanks).  i am sure you all know that but if your brake air pressure for any reason goes below that when you are driving, your parking brakes come on.  like it or not, ready or not.  

everyone hears about brake cans and you can see them on each wheel.  remember they can only leak air when the brakes are applied. 

thanks to those i called and bugged as i was figuring this all out.  

again,  i am no expert and i may be off in my explainations so i welcome any thoughts or additions.  

tom


Attached Files Thumbnail(s)
   
.pdf 060-AD-ISServiceDataSheet.pdf Size: 494.65 KB  Downloads: 12

2002 45'8" Newell Coach 608  Series 60 DDEC4/Allison World 6 Speed HD4000MH

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