[Jon]

The Meritor calipers used on coaches with the early disc brake set up on the steer and tag axles had two grease fittings inboard of the slack adjuster. Those were to allow the shaft from the slack adjuster to rotate freely. But those who tend to grease buses are usually the low men on the totem pole, with few skills so it was not uncommon for them to keep pumping grease into the fittings until grease was seen coming out of somewhere along the line.

Once grease is pumped in it can only escape from two places. It can ooze out around the seals, or if defective it can ooze out of the grease fitting. The problem is as a bus is driven and things tend to heat up the grease expands and has nowhere to go so it ultimately prevents the calipers from retracting, which causes more heat which continues to keep applying pressure to prevent caliper retraction.

I suspect a lot of brakes have been “repaired” by replacing calipers viewed as defective when in fact over greasing was the defect. I have never done this but suspect the easiest repair if over greased is to remove the two grease fittings and go for a ride that involves multiple long brake applications. I suspect excess grease will expand out of the grease fitting holes correcting the problem. Then to prevent a re-occurance when greasing in the future one or at most two shots in those fittings is all that is required.

[Unknown Member]

Ok. I will get under the bus and remove the grease fittings. As I’m not if it is still locked up, if so, don’t want to drive it, but I have also heard that by adjusting the brakes all the way down with the fittings removed it would also squeeze out the extra grease.

BTW Jessica figured out why my signature wasn’t showing up.

[Art]

Over greasing a caliper with the wrong grease, then getting it hot, can cause the brake to drag.

If you want to get the excess grease out of the caliper? this is what I would do:

There is a poppet fitting on the caliper between the 2 grease fittings. Remove it. It has about a 1/2″ hex head on it (give or take, I can’t remember exactly?).

On the slack adjuster, release the pawl (pull it outward, its spring loaded inward). I use a pair of dykes or flat blade screw driver to hold it out in the released position.

On the slack adjuster while holding the pawl out with the dykes, turn the square adjuster 4 or 5 complete 360 degree clockwise revolutions. This will force excess grease out the poppet fitting hole in the caliper.

Now release the pawl on the slack adjuster.

Reinstall the poppet fitting in the caliper.

Turn the square adjuster in the opposite direction, ccw, until the disc pads clamp the rotor firmly.

Release the pawl on the slack adjuster again, and turn the square adjuster cw 1/2 to 3/4 turn. This releases the pads slightly from the rotor.

Release the pawl and your done.

Proper grease is Meritor pt# A1779W283, which is clay based.

Meritor air disc brake manual mm4m: http://www.graphicvillage.org/meritor/mm4m.pdf

Meritor drum/cam brake manual is: http://www.graphicvillage.org/meritor/mm4.pdf

[Ronald]

Don, you the man! As always, thanks for sharing your wisdom.

[Jerry]

Just a word of caution…..Prior to self adjusting brakes all that was required was to tighten the slack adjuster as Don described and back it off anywhere from 1/3 to 3/4 turn to keep the shoes or disc off the braking surface of the drum or disc.

But later models have self adjusting slack adjusters and anyone fooling with them should get familiar with how they work and understand the correct way to verify they work properly, and adjust them. I do not remember if it is in the Prevost service manual or if I learned if from the Bendix certification class, but one way to adjust brakes with automatic slack adjusters is to loosen them by backing off the setting, and then fanning the brakes to allow them to self adjust.

I never did them that way, always manually adjusted them when working on the brakes, but can see how that method can work.

I have seen dire warnings about NOT manually adjusting self adjusting brakes.

[Steve]

Meritor will send you this gauge, It is to measure the free stroke of the slack adjuster, and it also measures stroke between short and long stroke brakes, It’s been a a couple of years since I messed with the brake calipers so I can’t remember everything. I found the proper free stroke on gauge is 1/2 turn back. Between that old Meritor brake Video and the Meritor hand book, Really helps understand the Meritor/Rockwell 1560 ADB (air disk brakes)

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Steve Magown

2001 Featherlite H3

West Monroe, LA

[glen]

The template part # TP4788

meritor.com/lod (Literature On Demand)