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Air brakes

I'm planning on having my brakes inspected and trying to decide between taking it to a shop or having a mobile mechanic come to my house and look at them. I'm leaning towards the mobile mechanic as I hope to be there with him and maybe get a little education on the brake system Plus I don't have to drive it somewhere and leave it. He specializes in heavy truck repair. I'm seeking advice from the group on what to look for to help minimize my chances of being taken advantage of. I'm not having a problem with the brakes, I just want to get them inspected.TIA
Michael & Roxene, Aussie the wonder dog & his daughter Luna the lunatic.
1993 Grand Villa Unihome 280 build #4203
36' 8.3 Cummins 300 hp- 2001 Chevrolet Tracker toad

Re: Air brakes

Reply #1 –
Just make sure who ever you use is familiar with disk brakes.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Air brakes

Reply #2 –
First thing I would suggest is to look at the thickness of the disc brake pad linings.  If you have a lot of lining left that would indicate that your brakes are probably functioning OK and wouldn't require major work.  Don't be surprised that the inboard and outboard pads are different thickness as they come that way new.  The pad thickness/wear should be similar on opposite sides of the same axle.  A thorough brake inspection should include pulling/inspecting/lubricating the slide pins and this is not difficult to do unless they are seized up.  The slide pins should come out easily and have a smooth and polished surface with little or no pitting.  If they are seized or heavily pitted they should be replaced and they are fairly expensive.  Meritor calls for a light coat of WD40 only for lubricating them.
George Mann
2002 U320 #5934
2017 Rubicon
2013 BMW GS
Waterford MI

Re: Air brakes

Reply #3 –
This is definitely a case of "Knowledge is Power".
Highly unlikely the mobile mechanic has seen air disk brakes -especially on a 30 year old vehicle.  There nothing difficult about them; just not used in trucks back then; I think mostly fire trucks and similar emergency vehicles and of course, Foretravels.  Probably the only motorhome manufacture to use them back then.

The mobile mechanic might be good or he might not be.  I think it's worth a shot, but you will need to find out on your own.  With some knowledge you can gain by researching you can find out if he is trying to snow job you or not.  For instance, I would ask him what kind of grease he would use on the brakes (hint: it's not normal chassis grease).  If he has never worked on Air Disks he should own up to it and tell you how he will approach it.  I don't think it's a problem is he hasn't, but he shouldn't be deceptive about it.

Fortunately there is good information on air disc brakes with photos showing what's OK and what needs replacing.
The forum library has the information here (see Air Disk Brake Maintenance.pdf and Meritor Disk Brake Maintenance Manual):
Air Brakes
You should be able to see the surface of the rotors and even the wear of the pads (via the exposed length of pin) by just by looking around with a flashlight.

I would also suggest using the search feature in the forum.  There a lot of threads on brakes and the correct grease to use and why.
Here's an old post from someone with a 1993: Does anyone have the part number for disc brake pads for my 1993 unihome?
It looks like a lot of the links a broken but there's still good information.  I noticed the P/N I had for front pads has been replaced with this one (KIT15627PM) : http://www.meritorpartsxpress.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10154&urlRequestType=Base&partNumber=KIT15627PM&langId=-1&catalogId=10051

John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Air brakes

Reply #4 –
Might also try the air brake holding test. It's something that you can do before he shows up.  I don't want to quote the wrong numbers but you should be able to find it on the forum.
  Something like press on the brake and it'll drop 5 lbs or so and the hold pressure for 2 minutes ?

    Ours wasn't holding air so I had a Mobil mechanic replace the rears with piggy backs and the fronts got new "dog bowls" (his term).  The rears were the problem with a few small holes but the fronts were not leaking yet.  BUT.. the fronts were cracked similar to how our tires would look when they need replacing.  So of course he replaced them also.

  Parts for the piggy backs were about $100.00 each. I did buy the complete air brake canister but left the part of the brake can attached to the coach in place. Hence the piggy back term. ( you tube).    The little rubber dog bowl things are cheap, like $6.00 bucks each. 
  Do watch the mechanic while he's doing this ( if you need it) you'll get a great education along with lots of you tube videos helps. 

 Also it seems our Foretravel's have about the smallest air disk brake systems out there.  My brake cans in back were 20/30s and 30/30s are way more common. The fronts are even smaller. At least on a Grand Villa U280. 

  Labor for the service was $300.00 and I bought all the parts.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Air brakes

Reply #5 –
A couple of pics to follow up on previous post.
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: Air brakes

Reply #6 –
Use correct high temp grease, then purge it all out. Use CorrosionX on slide pins.

Re: Air brakes

Reply #7 –
Other than the special Bentonite thickened high temperature grease you need to use, here's some solid information we all need to know.

https://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/brake_safety_systems_02-14.pdf
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Air brakes

Reply #8 –
The pins collect road grime and if you operate on dirty roads they will also collect road salts. I prefer to remove and clean bores and shafts. Wd40 and reassemble every couple of years for me. They can be a real bear to remove the first time but should be fine after. I use anti seize inside of the mount on the lock cam. Not so much about the lock wedge than the jst the opening. Corrosion pitting will be in the exposed areas and look like new were they are in the bore. Install the helper springs. Cheap insurance IMO. Once you get them up to speed next service wont be as bad. Ive seen rear lower pins you would have thought were frozen in place never to be removed again. They all come out eventually.

Re: Air brakes

Reply #9 –
Yup, your air disk brakes are unique, but not difficult to service.

But it is critical that it be done correctly-- correct grease, correct grease purge procedure and check the slide pins carefully.  If pitted, replace them.  If good just lube LIGHTLY as mentioned above.

I would absolutely recommend AGAINST using anyone who is not familiar with air disk brakes.  Check with your local fire station to see who services theirs.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Air brakes

Reply #10 –
I would have misgivings about a mobile mechanic having experience with air disc brakes. I second Brett's suggestion on asking at the local fire station who does their brakes even though when I needed to do mine I did not take his advice which I should have. Most truck repair places only know drum brakes and only  to replace parts. At least in my experience it didn't turn out well for me to get somebody else to do it, and instead invest in the tools and knowledge and time to try to work on it yourself if possible.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: Air brakes

Reply #11 –
So your telling me that in 2024 most trucks still run drum brakes ?
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR
 

Re: Air brakes

Reply #12 –
Quote from: Bob & Sue –
So your telling me that in 2024 most trucks still run drum brakes ?

On the rear, yes.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean