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 > Air Brake Adjustment

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auctions-r-us

Boyd, TX

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Posted: 01/22/05 07:37am Link  |  Print  |  Notify Moderator

How do you adjust the air brakes? I know truckers adjust theirs. When do you know they need adjustment? Thanks Scott

Triker33

Homestead, FL

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Posted: 01/22/05 07:46am Link  |  Print  |  Notify Moderator

My air breaks are self adjusting on a Freightliner chassis.

AIR BRAKES CHECK
Start engine and let air pressure build up.

Block wheels (use chocks that can be purchased from an RV supply store and chock the outside
dual on each side. Be sure to insert a chock in front and behind the tire to ensure no vehicle
movement. Parking on level ground when you do this is a big help. After this is done and you are
sure your MH can not move RELEASE YOUR PARK BRAKE.

Your brake pressure should be at max. Now fan your brakes to 85psi. NOW ENGAGE YOUR
PARK BRAKE AGAIN. Compressor should cut in and watch to ensure a return to full pressure.

When you have reached max pressure and the compressor has cut out RELEASE YOUR PARK
BRAKE AGAIN AND SHUT OFF THE ENGINE.

MAKE FULL BRAKE APPLICATION ( be sure you have released your park brake before you do this or you will damage the system.) Hold the pedal all the way to the bottom for one minute.
Watch your air gages as they should not move ( allowable loss in this mode for 60 seconds is 3 psi. Listen for audible leaks as you wait for the 60 seconds to expire. After 60 seconds release the pedal. (YOUR AUTO SLACK ADJUSTERS WILL SET UP AUTOMATICALLY DURING THIS PROCEDURE.)

Turn on key... fan brakes to 80psi. LOW AIR WARNING SHOULD START. continue to fan down
to 20 psi by now your park brake will have engaged automatically although you will not have any
indication of this.

Start engine and run at 1000rpm using your cruise setting. Time 3 minuets. In this time your air pressure should be up to between 50 and 90 psi. This will tell you your compressor is functioning
properly.

Apply park brake.

Ames

South Central Florida

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Posted: 01/22/05 10:28am Link  |  Print  |  Notify Moderator

If you have S cam brakes and they are manually adjusted a friend of mine who is the head of our city garage and an ex National Guard section cheif said to tighten them down then back off one half turn and they will be in proper adjustment. Takes about 10 minites or less per wheel. With disc brakes no adjustment is necessary and some of the newer chassis have auto slack adjustors similer to the rear drum adjustors on cars.


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John Blue

Brandon, FL.

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Posted: 01/22/05 07:55am Link  |  Print  |  Notify Moderator

We have air disk brakes. In all the years of use we have never had to adjust anything. I think system is from Rockwell. System works very well.


John Blue
Brandon, FL.
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Kajtek1

CA

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Posted: 01/22/05 09:52am Link  |  Print  |  Notify Moderator

Manual slack adjusters take 9/16 wrench. It is a bit tricky, because the sleeve behind the adjusting bolt is a locking sleeve and needs to be pushed with wrench. I found deep socket working the best.
Good idea is to try to find a manual, but rule of thumb says, that in properly adjusted brakes, the arm of adjuster and the rod suppose to make 90 degree angle when the brake is applied.
It takes 2 persons, one at the brake pedal to push it and the second person under the coach. If you use the engine to run the compressor, you might need walkie-talkie.
I've been using shop compressor for the coach, what made the job much quieter.

BattChief

Edmond, Oklahoma, USA

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Posted: 01/22/05 07:49am Link  |  Print  |  Notify Moderator

It would depend on the type of brakes you have, whether they are disc or drum. They should have slack adjusters on them, but they should also be auto adjusting. The brakes should adjust themselves each time you apply the brake while moving backwards. I wouldn't recommend adjusting them yourself unless you are really mechanically inclined. Too tight of an adjustment could cause a fire in the brakes.

If you can identify the brand (such as Meritor), you might be able to find information on the website of the manuafacturer of your brake to determine proper adjusting procedures. However, if they are not adjusting properly on their own, it may be something you would want to take to a mechanic to find out why the slack adjusters aren't working.

JMTCW.....


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matsprt

So Cal

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Posted: 01/22/05 11:38am Link  |  Print  |  Notify Moderator

God help the MH people. No wonder there are the troubles with brakes. Everyone has only parts of the answer right....

IF you have drum / "S" cam brakes they are correct and MOST likely you have auto adjusting slacks.

The adjustment takes <1 minute per side IF you know what your doing.
Kajtek1 was about right. I stay with the box end 9/16 wrench. There is a spring loaded collar on the slack that you depress while turning to snug up the brakes into contact with the drum. Once the brake shoes are tight up against the drum TAP the drum with the wrench. It should make a dull sound.

Now like mentioned by Ames back off 1/2 turn. TAP the drum again, it should sound tinny. That indicates the brake shoes are now OFF the drum. If it's still a dull sound you need to back them off another 1/4 turn.

If you have to back them off more, then you have a drum that's out of round/worn out and should be replaced.

This is a SIMPLISTIC answer to how to adjust brakes. BTW auto slacks DO NOT always work, especially if not greased at proper maintenance intervals. Just ask the truckers that get tickets at the scales houses. They all say "but I have auto slacks" and the CHP says too bad, there out of adjustment/not working. Fix them.

NOW BIG DISCLAIMER !!! DO NOT ADJUST BRAKES UNLESS YOU KNOW WHAT YOU ARE DOING !!

Pay the $20 bucks and have the mechanic do it.
Currently in California unless you are certified to work on air brakes even the owners are not supposed to adjust brakes.

I know there are any number of variations to the above adjustment procedure. We have not even discussed the throw measurement the CHP uses.

Enough said. I'm off my soapbox.


Never argue with an idiot, they take you down to their level and beat you with more experience....

bwtrump

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Posted: 01/22/05 11:21am Link  |  Print  |  Notify Moderator

How to know when they need adjusted? Generally, on the air brake chamber there is an orange mark on the plunger. While the brakes are set, you should not be able to see this. If you do see the mark/tape on the plunger, the brakes need adjusted up.
The manual slack adjuster has been addressed, so I won't go into that.

This is done with brakes released and wheels chocked, keys removed and sign on steering wheel stating someone under vehicle:
For automatic slack adjusters that haven't adjusted up, they need replaced. But to adjust them manually, you go to the tip of the adjuster (in relation to the cam) and find a 1/4" square "bolt". It will turn only one way, and that is what takes the slack up. Tighten them until resistance is felt on the bolt. Then on the side of the aduster, there is a plug looking thing with a spring loaded pin in it. You will need to put a knife blade between the plug and pin. This is called a pawl--it keeps the adjuster from backing off and may be the source of why the unit doesn't adjust or backs off. As you pry the pin out, it releases tension on the pawl. You will need to back off the bolt at the top about 1/2 to 3/4 turn to allow some free play in the brakes. If the pin/pawl won't come out, you can remove the entire plug looking assembly and achieve the same result, and you can check for problems on the pawl. And yes, the pawl is replaceable. Usually made by Meritor.
I know thats a lot, but if you watch someone do it once, its no big deal after that. Also, grease the adjuster and the cam while you are there.
If this is greek, please, by all means take it to the shop and let them do it. BT


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auctions-r-us

Boyd, TX

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Posted: 01/22/05 11:13am Link  |  Print  |  Notify Moderator

Thank you for your answers. MH is 93 HR dp on sparten chassis.Are self adjusting on newer coaches only. Scott

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