Parking brake not holding, Air drum brake on shaft.

[Heather F]

Have 2001 Monaco Knight

Have had issues with parking brake only holding on a slight incline long enough for me to get out and put a chock under the wheel.  Last march found a place with parts, had pads and new springs put on, one spring was missing, worked good for 2 weeks, then when I would engage the brake it would take 20-30 seconds to fully set.  I would hold the foot brake, set the parking brake and count to 30. Replaced the push/pull valve and low pressure valve to fix this issue.  4 days later after driving on a ruff road, I stopped for fuel and it kept rolling back, was able to pull forward to a flatter spot so it would hold long enough to get a chock under it. Later had to pull forward to get the chock out. Looked at the brake and nothing looks different, pads are against the drum, when brakes are released it looks like only one pad is moving away from the drum. This is an Air brake on the drive shaft.  It looks like it can not be adjusted anymore, the pads are only 2 months old.  I am near springfield IL heading towards Kansas City if there is a shop that know these brakes.

 

Heather

 

  

[Ivan K]

I have only seen this type of brake on big ford's and they weren't air released but that should make no dirrence when parked. Has anyone measured the drum diameter compared to spec? The maximum diameter should be cast into the drum. If the last picture is with brake applied, the pads appears not to be fully in contact with the drum? The lining also looks quite thin, you are probably right about the brake not releasing fully (lack of air or actuator stuck?) and wearing the drum and lining. 

[Heather F]

36 minutes ago, Ivan K said:

I have only seen this type of brake on big ford's and they weren't air released but that should make no dirrence when parked. Has anyone measured the drum diameter compared to spec? The maximum diameter should be cast into the drum. If the last picture is with brake applied, the pads appears not to be fully in contact with the drum? The lining also looks quite thin, you are probably right about the brake not releasing fully (lack of air or actuator stuck?) and wearing the drum and lining. 

I just has the pads and springs replaced by onsite trucking in Phoenix AZ.  I had other RV and truck repair shops look at it and they couldn't find replacement pads.  I know to adjust it I turn the nut on the arm but I don't know which way, does the arm need to shorten or lengthen? 

[Frank Bergamo]

Had one of these brakes on an Executive Diplomat years ago. If I remember correctly, lengthening the rod with the clevis puts more pressure on the brake shoes to the drum. If you get it to tight, then shoes will drag on drum. Need to find happy medium for adjustment. One thing that helps is keeping drum and brake shoes clean with brake cleaner. Your picture looks like drum and shoes are pretty greased up. Sprayed mine on a regular basis and seemed to help with brake holding when needed. Hope this helps.

[Ivan K]

Which ever way the lever travels when you apply the brake (release air), you could try make its travel a bit longer but still not so much that it could not release. I have no idea about the actuator that is moving it but expect it to have a strong spring inside of it, just like regular park brake air chambers. It does not make sense that you had to wait for the brake to apply unless it had a plugged or bad exhaust valve. But if the drum is worn, only part of the linings will have contact with it.

[Heather F]

19 hours ago, Ivan K said:

I have only seen this type of brake on big ford's and they weren't air released but that should make no dirrence when parked. Has anyone measured the drum diameter compared to spec? The maximum diameter should be cast into the drum. If the last picture is with brake applied, the pads appears not to be fully in contact with the drum? The lining also looks quite thin, you are probably right about the brake not releasing fully (lack of air or actuator stuck?) and wearing the drum and lining. 

Last pic is with the prake off, so one side is releasing the other didnt move much. Trying to get specs from last shop that replaced the pads in March, I agree they look thin.

18 hours ago, Frank Bergamo said:

Had one of these brakes on an Executive Diplomat years ago. If I remember correctly, lengthening the rod with the clevis puts more pressure on the brake shoes to the drum. If you get it to tight, then shoes will drag on drum. Need to find happy medium for adjustment. One thing that helps is keeping drum and brake shoes clean with brake cleaner. Your picture looks like drum and shoes are pretty greased up. Sprayed mine on a regular basis and seemed to help with brake holding when needed. Hope this helps.

Thanks, Sprayed brake cleaner on it and it helped a little, I can stop long enough on slight incline ( fuel stations) to get a chock down.  In KC will look for a shop to make sure its done right since I am heading west toward mountains.

18 hours ago, Ivan K said:

Which ever way the lever travels when you apply the brake (release air), you could try make its travel a bit longer but still not so much that it could not release. I have no idea about the actuator that is moving it but expect it to have a strong spring inside of it, just like regular park brake air chambers. It does not make sense that you had to wait for the brake to apply unless it had a plugged or bad exhaust valve. But if the drum is worn, only part of the linings will have contact with it.

I fixed the waiting part by replaceing the push/pull plunger, I just had the pads replaced so it could be the drum.  Will find a shop in KC to get it looked at.

[96 EVO]

Being a driveshaft brake, the only way that drum should be worn down would be the shoe's set too tight at some point in it's life!

Or, at some time it was driven with the parking brake on.

Don't read this wrong. I'm not saying you did this! You seem way too knowledgeable to do that!

Plus, we don't even know for sure it is the drum that is worn! 

Edited May 21, 2023 by 96 EVO

[Ivylog]

Air chambers push and a weak spring returns it…lengthen the rod.

[Heather F]

12 hours ago, 96 EVO said:

Being a driveshaft brake, the only way that drum should be worn down would be the shoe's set too tight at some point in it's life!

Or, at some time it was driven with the parking brake on.

Don't read this wrong. I'm not saying you did this! You seem way too knowledgeable to do that!

Plus, we don't even know for sure it is the drum that is worn! 

Had the shoes and springs changed in March, so I know it hasn't been driven with the brakes on have driven about 3000 miles since then, looks like one of the shoes is not releasing fully since I have a lot of brake dust for the parking brake. so looking into parts not moving correctly.

3 hours ago, Ivylog said:

Air chambers push and a weak spring returns it…lengthen the rod.

Thanks, I think they put wrong shoes and springs on last time, the rode is all the way out.

[jacwjames]

Heather,

Here is a post on IRV2 that might help.  Same year/model coach with a drive line brake.  From the post it has a brake canister that actually does the work of moving the brake shoes in/out via a cable.  You might to check the whole system and make sure the canister is operating correctly. 

https://www.irv2.com/forums/f115/2001-monaco-knight-32l-parking-break-problem-394191.html

I read other none Monaco posts and on one someone made a very good point.  The brake shoes themselves shouldn't wear out since the coach should be parked and not moving when the brake is in use.  If the shoes are wore it means it had not been releasing correctly or the coach was driven with the brake on.   Another possibility to cause the shoes to wear is that they are not suspended correctly within the drum and it wears one side or the other. 

On my coach I have an alarm that sounds if I try to move the coach with the brake on.  Does your alarm work. 

 

~40 years ago we had equipment that had drive line brakes and had nothing but problems with them.  Most of the time it was operator error caused by them not releasing the parking brake.  It would take less then a minute for them to ruin a parking brake. 

Edited May 21, 2023 by jacwjames

[Robert92867]

I concur with all the others re "lengthen to increase brake pressure".  Also, your rod adjustment looks normal.  Mine looks like it and has never been moved.

[genemenne]

Here are a couple YouTube videos which are informative: 

One popular driveline parking brake is Meritor DCM 1204 (I believe the 4 designates the shoe width in inches - there is also DCM 1203 and DCM 1205).  Note that this is only the drum and shoe assembly and actuating arm but does NOT include any adjustment mechanism.  There is no internal adjusting mechanism.  The rest of the actuating and adjusting mechanism, whether rod, electrical, cable, hydraulic or air operated, is supplied by the vehicle manufacturer.

In your case being air operated, I would expect your PB to be fully applied or released in 1-2 seconds.  In addition, a correctly designed, installed and adjusted drivelive PB should be able to hold a fully loaded vehicle on an xx% grade.  I don't recall what the xx% is, but it is spelled out in an FMVSS and the manufacturer must certify that the vehicle meets it.  I suspect is at least 10%.

Gene

 

[Heather F]

It looks like when the brake is released the shoes are to loose, can be wiggled by hand and they are not touching evenly, the curve of the shoes is not the same as the drum.  I have found a mechanic in KC that is looking at it.  Thanks for all the input.  I will update with the fix.

[Heather F]

My fix.  The Air Brake Chamber was not moving correctly it would move a little stop and then move a little more, it did this both in and out.  Also the Brake drum had a barely visible dent on the edge caused the pads to wear on one edge.  So new Air Brake Chamber, Brake drum and pads.  Works great.

Edited June 19, 2023 by Heather F