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Topic: Brake pressure major drop (Read 664 times) previous topic - next topic

Brake pressure major drop

My brakes are loosing pressure very quickly!
I blocked the suspension and had the break pedal pressed at full pressure and all the air escaped in a minute or less! The air is escaping through a vent hole in the spring cage. Would that indicate a leak in the diaphragm?
How should I proceed?
1997 U270 36'
Build #5115
2014 Jeep Rubicon towed
1972 Boston Whaler 16'
Charlie

Re: Brake pressure major drop

Reply #1 –
You have a blown diaphragm. It's fairly easy to replace the diaphragm or you could
get a new brake pot.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Brake pressure major drop

Reply #2 –
Quote from: Want2rv –
My brakes are loosing pressure very quickly!
I blocked the suspension and had the break pedal pressed at full pressure and all the air escaped in a minute or less! The air is escaping through a vent hole in the spring cage. Would that indicate a leak in the diaphragm?
How should I proceed?

Time for a whole new assembly.  NAPA?  There are NAPA truck stores.

I'm replacing my air dryer for the first time and I've ordered up a Midland re-built air dryer rather than refurbishing what I have in my hands.  Why?  Because I'm old and I don't know the history of the air dryer I removed.

12 minute video about a bad rear brake can.

https://youtu.be/fQhhtsMJihE
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: Brake pressure major drop

Reply #3 –
I'm going to replace the brake can. I understand I need to cage the spring, are there any other safety issues I need to address?
Should I replace both rear cans?
1997 U270 36'
Build #5115
2014 Jeep Rubicon towed
1972 Boston Whaler 16'
Charlie

Re: Brake pressure major drop

Reply #4 –
I would do both while I had every thing out. After you get the old ones off un cage them so you can get the push rods on the new ones cut the right length. Another tip put a nut on the push rod before you cut them off the run the nut off helps straighten the threads out after you cut them. The re cage them to install.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Brake pressure major drop

Reply #5 –
Parts are cheap for the cans and easy to replace. Good videos on YouTube on how to do it. I did a failed DD3 on my bus but blasted all the metal and zinc chromated it. Took a couple of hours.

If buying new cans, stay with the same size as larger may seem better but will upset front to rear braking balance, especially in the wet. An inspection for rust/corrosion will tell if your can is a candidate.

Caging tool may be on the side of the can.

Consider a spin-on dryer. Not expensive and only take a couple of minutes to R&R the new element. See old posts.

Pierce

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Brake pressure major drop

Reply #6 –
Well...I tried to take the quick and easy path!
I got replacement diaphragms, but was unable to mate them in the can without leaking!
A 70 year old on his back couldn't wrestle it all into place!
I took this route because it seemed quicker and easier, but I can't mate the two sections without air leaks!! Also I wasn't comfortable with the required brake adjustments.
Replacing the entire canister units is the correct path!
Time for plan B!
Thanks all for your input!
1997 U270 36'
Build #5115
2014 Jeep Rubicon towed
1972 Boston Whaler 16'
Charlie

Re: Brake pressure major drop

Reply #7 –
I will suggest that replacing the diaphragm is a bad idea. A certified mechanic would never do that. SOP is
to  replace the whole can. Air brakes should not be played with if you are not a pro. Everyone wants to save money but diy air brake repairs are not the place to save a few bucks.

Re: Brake pressure major drop

Reply #8 –
Probably I should of just suggested to change the can although if the can is in good
shape I would probably change the diaphragm but I would do the repair on the bench.
I have done it both ways.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Brake pressure major drop

Reply #9 –
Want2rv wrote:

> Well...I tried to take the quick and easy path!

There is not quick and easy path.  There is only work.

> I got replacement diaphragms, but was unable to mate them in the can without leaking!
A 70 year old on his back couldn't wrestle it all into place!

That's why we remove the whole assemble and work on our work bench with the huge vise.

> I took this route because it seemed quicker and easier, but I can't mate the two sections without air leaks!! Also I wasn't comfortable with the required brake adjustments.

If you're not comfortable with brake adjustments you should probably call the mobile service mechanic in to do the repair.

> Replacing the entire canister units is the correct path!

And that is why I'm waiting for the arrival of a re-built air dryer.  I just want to put things back the way there were, and if I live long enough to do it again, maybe I'll make the necessary modifications for a new air dryer with a spin on desiccant cartridge.  But right now I have to pull the entire air dryer to change the desiccant cartridge anyway.


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: Brake pressure major drop

Reply #10 –
I just purchased 2 new brake canisters!
I'm going to install them, if I run into trouble, I'll call a mobile mechanic.
If the first one goes on easily, I'll install the second one, if not, the Cummins repair shop is just a few miles down the road.
Thanks for the advice!
1997 U270 36'
Build #5115
2014 Jeep Rubicon towed
1972 Boston Whaler 16'
Charlie

Re: Brake pressure major drop

Reply #11 –
Charlie, send me you phone number in a pm. I'll walk you through the process if you like. I've done a bunch of then I'm in mountain time zone.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Brake pressure major drop

Reply #12 –
Bruce, not sure how to pm through this site.
So glad your willing to help!!!
Thanks
1997 U270 36'
Build #5115
2014 Jeep Rubicon towed
1972 Boston Whaler 16'
Charlie

Re: Brake pressure major drop

Reply #13 –
Quote from: Want2rv –
not sure how to pm through this site.

Move cursor under his smiling face and left click on the box that is "send message"  That will lead you where you need to go to send him a private message.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."
 

Re: Brake pressure major drop

Reply #14 –
I successfully installed the air brake canister!
I learned a lot and the second one will be much easier!!!
Thanks to Bbean for his valuable assistance!
1997 U270 36'
Build #5115
2014 Jeep Rubicon towed
1972 Boston Whaler 16'
Charlie