Adjusting the park airbrake

[Mike in Va]

I have a 2001 HR Ambassador with the 2100 allision transmission. I have a shift knob and not a swift pad. I also don't have a p {park} selection on my dash. When I park I put the selector in N and pull the air brake on. I just installed all new brake pads, rotors and calibers on all four sides. Over the weekend I  was on a steep hill and set the air brake and the mh started to roll backwards. This has never happen before, but its the first time I've had the mh on such a steep hill. Its works ok on flat land. How do and how hard is it to adjust the air brake? Thanks     

[Frank McElroy]

Something isn't right.  Either the slack adjusters were not set properly or the brakes were caged to releases the parking brakes while doing the brake shoe replacement and the caged brake chambers were not fully released after the repair.  If you have the parking brake set then in either forward of reverse gear when you gently press on the accelerator, the coach should not move.

I'm surprised that the shop who did the work didn't catch this problem when they should have performed an air brake function test after the repairs. 

Attached is a link to a file in our file downloads that will provide additional information on how to perform an air brake pre-trip check.

 

[Ivylog]

There isn’t an adjustment. It’s a spring in the air chamber on the drive axle. Agree it may be because there is to much travel…slack adjusters not adjusted correctly. I would take it back as you probably do not have full braking too. Doubt they left the T headed caging bolts in the air chamber as you wouldn’t have any rear brakes.

[Mike in Va]

I contacted the shop that installed the new brakes and accessories,  they said the park air brake is separate from the work they've done. Have an appointment for this Monday so I hope they can get it fixed. 

[redstickbill]

Number one rule: Chock the wheels when working on the coach.

Bill B 07 Dynasty

[Frank McElroy]

Mike, A simple visual inspection, without going under the coach, will allow you to determine if the service center failed to remove the brake chamber cage bolts.  I find it hard to believe they didn't fully remove the cage bolts and store them on the side of the chamber but it's easy to visually check.  The procedure for Caging drive axle brakes to release the parking brake is also explained in your coach owners manual.

Before bringing your coach back to the service center, I would perform the procedure explained in the attached link to my previous posting - page 2 - step 5 for properly adjusting the auto slack adjusters (assuming that the auto slack adjusters are setup and working properly).  This is easily done inside your coach from the drivers seat but be sure that you do this with the parking brake released and if on a slope with the wheels chocked.

I don't think you have manual slack adjusters but if you do, you will need to go to back to the service center or learn how to adjust them yourself.

[Harvey Babb]

You say that you have replaced all the brake pads and shoes. Be aware that brand new pads, and especially shoes, do not produce full braking effort until they wear in. 

Shoe type brakes are largely self actuating and can show a profound difference in ability after a few stops from high speed. In addition, the wear in is directional. Wearing in with forward stops does not have as much effect on rearward stopping action so full wear in is slower to occur.

 

[Larry Laursen]

The 2001 Ambassador is a air over hydraulic system.  I am not sure how the part brake is applied on that system.  It may be a drum on the driveshaft.  However, it is probably spring loaded but not at the wheel locations as on a full air chassis.

[Mike in Va]

Larry I think you are right. Trying to get the time to go under the rv and take a look. Will have more info in a little while. Thanks

[Frank McElroy]

Larry, good point - yep, an air over hydraulic system would be a lot different and could very well have a driveshaft drum for the parking brake.  That's likely why the service shop told the OP that their repairs had nothing to do with the parking brake.  Although I would have thought that a shop doing a brake job would also verify the proper operation of the parking brake.

[Larry Laursen]

Frank,

I looked at the owners manual here Ambassador 01 sect 1.qxd (digitaloceanspaces.com)

The Park function is in the transmission and says a pawl on page 253.

If all else fails read the instructions😁😁

[Mike in Va]

Larry you were right. Have a drum in front of transmission with pads inside. The pads look good so I will go on line and take a look at the manual. The only manual I have is very basic. The shop is pretty good but I guess they were afraid to preform any work not on work order. Thanks

[Frank McElroy]

It will be interesting to find out what Mike sees when he looks.  Page 238 takes about using air to release the parking brake.  So I'm thinking there might be both a driveshaft drum brake and a transmission pawl.

[Frank Bergamo]

Mike, I had the setup you have on a Executive Diplomat with the same problem of coach not holding on an incline. Used some brake cleaner on the drum and shoes since it is exposed to the elements. Improved the brake holding ability, but never could get it to hold completely on a steep incline. Just learned to park on a fairly level spot and also carried some wood blocks to block wheels. Not the ideal situation but it worked for me. Will be interested in your solution, as I never felt comfortable with blocking wheels and then going to sleep at night.

[Mike in Va]

Frank just came out from under my mh. I have a shift knob not a pad and I don't have a park selection on my mh. When I park, the selector goes in N and then the air brake is applied.  I found an air container with a long rod that goes over to the adjuster. Now if I can find how much to adjust without going to far.

I will try cleaning like u said. I will ask the garage about this on Monday. Have an appointment because my left rear abs sensors is causing the abs light to come on. I don't want to break anything by adjusting it too much. Will let you know what they say. Thanks so much for the help. 

[Gary Cole]

Wonder what the expected service life of a typically compressed spring of that type is? Could age be a factor?

[Mike in Va]

Frank, Took my MH to the garage today and they were able to adjust the brake some. Said it looked like it hasn't be adjusted in a LONG time, but the pads looked good. Also found some road grime and grease. It was cleaned good using brake cleaner and they told me it should take care of my problem. I asked about your problem and their response was that your brake should hold the weight of your MH even on an incline. They told me that these type of brakes are put on large delivery trucks with heavy weight and work ok.  Sorry I don't have any answers for you other then keep them adjusted and clean.   

[Frank Bergamo]

Mike,

thanks for the update. I no longer own the motor home in question, so hopefully you have figured out your problem with your park brake. Good luck, hopefully it holds with no more problems.

[Frank McElroy]

Mike - It sounds like your service center fixed the problem.  Years ago I had a motorhome (not a Monaco) with a similar drive shaft brake.  On mine I adjusted it only one time shortly after I got the coach new.  On mine, the adjustment was just like a car with brake drums where you needed to properly adjust the star wheel between the two brake shoes.  My only problem was that the access hole was on the drum.  So I had to jack up one rear wheel in order to rotate the drive shaft to align the access hole with the star adjustment wheel.  In my case, after adjustment, the parking brake would hold on any steep incline I ever encountered in over 60,000 miles that I used the coach.  Even so, whenever I parked at a campground, I still chocked the wheels for safety.  Even on my new coach with full air brakes, I still chock the drive wheel when I'm in a campground.