# air over hydraulic



## Guest (Sep 5, 2007)

Does anyone out there have a diesel coach that has air brakes but they are hydralic,,,
I have a 95 coachman in my shop now that has a brake prob,, the rear brakes just kinda apply when u put on the brakes,,,
The customer thought he  had a brake prob with the disk pads ,, but they are like brand new,, his complaint was that he never really felt like he had brakes...
We ckd the pads for and aft ,, and all were good ,,, but when the parking brake button is pulled out ,, i can still turn the back wheels,,, i have worked on big semis alot ,, but i have never seen a air powered hydraulic unit,,
The rear brakes have 2 master cylinders that are powered by air ,, the brake pods push in the master cyls and aplly the rear brakes...
I am going to do more testing ,, tomm on this ,, but just was wondering if anyone else had this kinda setup????


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## Bush70 (Sep 6, 2007)

Re: air over hydraulic

In air over hyd. the park brake is air. There should be a can and a set of shoes on the drive shaft. There is a linkage there you can adj. or you may have bad shoes. As for the service brakes, not alot different than vac. boost except air instead of vac. Good luck.


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## Guest (Sep 6, 2007)

Re: air over hydraulic

This coach has disc on the back ,, and the air pods push the master cylinders ,, i talked to a rep from coachman today and he said that the brkes should be locked up on all rear wheels,, the front are not incorporated into the park brake,,, but anyway i think i found the prob,,, the rubber hose from the 2 maters is kinda old and like most know about a regular car brake system ,, these hoses can break down inside and not let the fluid back out ,, well anyway gonna get on it tomm,, i hope,, had to many calls today to mess withit ,, but the customer is not worried about it since he is getting ready to put it up for the winter,,, i'll keep u posted on the outcome of this,,,,
Bty thanks Bush for the insight ,, i have worked on alot of coaches , gas , diesel and so on ,, done brakes ,, engine OH ,, differential rebuilds and even some tranny rebuilds ,,, i worked for Kenworth for many years ,, but have never seen this kinda setup ,,, i  would take a interior restore over this ,,, JK  :laugh:


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## Guest (Sep 8, 2007)

Re: air over hydraulic

I found the prob ,, it was in one of the master cylinders ,,, bty the park brake is on the wheels ,, it has drum brakes inside the disk rotors ,, and it works  fine but the main brakes on the rear are not functioning ,,, i found a kinked air line to the master cyl to the rear brakes  ,, but that was only half the prob ,, i'm going to replace the master cyl to the rear as soon as it gets here...
Thanks for the post...


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## Bush70 (Sep 9, 2007)

Re: air over hydraulic

always something differant. The ones I have seen have the can on the driveshaft. ( freightliner chassis) I don't think you said what chassis. Just curious. Good luck


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## Guest (Sep 9, 2007)

Re: air over hydraulic

It has a spartan chassis ,, and yes i could not believe it either ,, but the park brake is inside the rotors,, kinda like a chevy tahoe or any new pickup ...
But thanks again for the reply ,, as they say 4 eyes are better than 2 or 2 minds better than 1 ,,, what's keft of mine   
I'LL keep u posted on the out come ,, but as so far ,, i am getting hardly any fluid outta the rear brake master cylinder (this was at the master cyl ) I think the kinked air line had some to with it ,,,,


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