Relay value

[Geoff Weeks]

5 minutes ago, Joey Mack said:

Ok.. im sorry.  Im wrong about the diaphragm..  I guess all those times i was isolating a bad brake chamber was in error.. I will back out if this thread so as not to post incorrect statements.

Not really, if you changed the whole chamber, with a service 30/30 you will be changing the correct part. I still have E brake chambers that you can service the spring brake side, either diaphragm or piston type, but those are what? 30-40 year old? When did the "idiot proof" "sealed chambers come out?

 Diaphragms leak to the outside, the piston rod seals leak chamber to chamber, but with the idiot-proof chambers, the only way to fix is to replace the service 30/30. In the old ones you can take the big Phillips head screw off one piston, remove the interchamber rod and replace the seals, though not many did. 

[Xe18]

7 hours ago, Joey Mack said:

Is the data tag still on the valve? You may just have to remove it to I.D. it. Mechohaulic makes a good suggestion. At $600.00 i would take it apart and inspect it and clean it, and try to rebuild it. Is the air system Bendix or Wabco? 

Bendix

[Xe18]

8 hours ago, 67RModel said:

Did their price include installation or was that just for the part? Mack might be asking double what its worth. Get the part number off of it and see what one can be obtained for from an independent supplier.

Just part. Part# on the valve is Bendix T-5019505

[Xe18]

3 hours ago, mechohaulic said:

noticed no one questioned WHEN is the valve leaking ;; constant (shouldn't be) ; during service brake application or after service brake applied and released? might make a difference where the hunt starts.

Constantly no matter brake apply or release 

[mechohaulic]

37 minutes ago, Xe18 said:

Constantly no matter brake apply or release 

being a constant leak WITH  parking brakes set; I'd go with earlier post I wrote and look at the lower section of that valve. if you have a "helper" a quick check would be to BLOCK the wheels safely; release the parking brake unit having full air pressure and truck shut off ; have someone have their hand on bottom side of leaking valve ; helper in cab step on brake pedal; air leak changes /slows chances are it's the flat rubber diaphragm in valve. to replace bottom kit ::parking brake set ; make sure all air is drained from tanks. larger pair of snap ring pliers (also safety glasses on ) , remove the snap ring .valve assembly has slight spring pressure. important thing air tanks MUST be empty.

[Geoff Weeks]

21 minutes ago, mechohaulic said:

bchances are it's the flat rubber diaphragm in valve. 

In the link I posted to the Bendix "manual" on that valve, it is all just plain O rings, and the manual even lists the size, so you can go to where you buy O rings, and have them all before you start.

 There is a small chance that there is a small (internal) leak from the solenoid valve on the top, but think it is much more likely a piece of crud is stuck in the valve, disassemble, inspect and install new O rings. Cost would be the cost of the O rings, but if you have a good supplier, then less than $20 would be my guess.

Follow Mecho's testing to make sure it isn't some other valve backfeeding into this one.

edit:

If your a gambling man, leave the valve in place, don't mess with the top 1/2 and only take the snap ring off the outlet, and remove and replace the O rings that come out the bottom, clean the valve seat where the delivery valve seats. That is the most likely point of failure. Just two O rings.

Edited August 21 by Geoff Weeks

[Geoff Weeks]

That Bendix number come back to the ATR-6 which is what I posted the manual on.

[Xe18]

1 hour ago, Geoff Weeks said:

Follow Mecho's testing to make sure it isn't some other valve backfeeding into this one

No delivery port on that valve I can test for backfeeding. I’m the diagram there are two delivery ports but one got closed off and other one connect to other valve by metal pipe. 

[Geoff Weeks]

The two pipes go to ABS actuator valves then to hoses to the brake chambers, Make sure the brake chambers aren't backfeeding. The ABS valve on either side are just straight through unless the ABS is in action. The 3rd hose on the bottom should go to a quick-release on the spring brake circuit to prevent compounding (anti-compounding QR) . 

Any of these could backfeed it there is a problem "down stream"  all would only leak back when the parking brake is off. If your valve leaks with the parking brake on, then it is the valve itself. 

If it leaks all the time, whenever there is pressure in the air system, it is most likely the bottom portion of the valve, which can be taken out and cleaned and new O rings install by removing the snap ring (spring loaded parts behind the snap ring, so be ready to ketch them.

There is a small chance that solenoid valve on the top has a small leak, and I think that would be harder to repair/get parts for.  

For the cost of O rings, I would start at the bottom of the valve, if it leak all the time there is air in the system (parking brake on or off)

[Geoff Weeks]

All the outlet ports are marked with a red X

[Geoff Weeks]

In  this exploded diagram the possible leak points not including the solenoid valve are:

1) between the top face of part #6 and the body of the valve. Look for crud stuck in this location

2) O ring #10 seals valve # 6 to retainer #11, a bad O ring here would leak out the bottom

3) A bad O ring #9, unlikely as the is a stationary seal between # 11 and the valve body.

Of the three situation #1 is the most likely, followed closely by #2  O ring # 10 has to seal # 6 which slides in the O ring when valve #6 moves off its seat.

When at rest (no brake applied), any pressure in the outlet port vents out the center of part #6.  

Edited August 21 by Geoff Weeks

[mechohaulic]

top face on #6 is a flat rubber washer which 7 out of 10 times is the culprit, either crud or crack in washer if there is a constant leak.

[Geoff Weeks]

Since this valve appears to be a modified R12 relay valve with a different housing and top cover, I would guess one of the maintenance kits made for the R 12 would fit, with the disclaimer that I have not tried it and it is "at your own risk". 

[mechohaulic]

I would go with the R-12 kit 2831, has all the important parts for rebuild. if the piston #4 was cracked the supply air would bleed out through into service can lines  which would have a quick release valve leaking POSSIBLY. try a can of spray silicone with flex nozzle spraying into valve from bottom or take off a service line spray into valve. spray in service line not as effective since your spraying on top of piston . before spending  $600.oo ; I'd do everything possible to narrow down problem. course have to hope some/any of these kits still available.

[Geoff Weeks]

https://www.fleetpride.com/parts/bendix-relay-valve-5019003?srsltid=AfmBOoothJ8GDJg5FZA9xm-PFx7lUT3MHqGVL2fMJo4I9uhXx-RcOAt0

 

https://bigrigworld.com/r-12-valve-maintenance-kit-5002831bxw.html?srsltid=AfmBOorwRZIJ1V-s0PH8OMLysX30eh69XQT-XgBUVncCZS3TOPnO3KjJ

[Xe18]

Thank you so much for all your help. I disassembled bottom half today and cleaned all the parts and greased 2 oring and rubber washer. Done no more air leaks. I will get the rebuild kit next week for backup in case it leaks again later on. Again thank you all of your inputs and saved me couple hundred dollars. 

[Geoff Weeks]

The bottom kit in the screen shot likely has all you need. Again, these are R-12 kits and I haven't tried them on an ATR  as I have nothing as new as to have traction control. 

It is the kit listed at Fleetpride, but I have seen them cheaper.

[mechohaulic]

13 hours ago, Xe18 said:

Thank you so much for all your help. I disassembled bottom half today and cleaned all the parts and greased 2 oring and rubber washer. Done no more air leaks. I will get the rebuild kit next week for backup in case it leaks again later on. Again thank you all of your inputs and saved me couple hundred dollars. 

Thanks for update especially since it was positive results  not costing $600.oo

[Joey Mack]

mech, I believe you told him to remove that section and check it..  just sayin' 🍻

[mechohaulic]

6 minutes ago, Joey Mack said:

mech, I believe you told him to remove that section and check it..  just sayin' 🍻

the flat rubber "washer" on top of #6 -inlet/exhaust valve will do it almost every time under those conditions. even with the added ABS crap; it's still a basic valve from OLD SCHOOL . you can take a small house and add a porch ; it's still a small house 

[mechohaulic]

On 8/20/2025 at 9:11 PM, Geoff Weeks said:

In the link I posted to the Bendix "manual" on that valve, it is all just plain O rings, and the manual even lists the size, so you can go to where you buy O rings, and have them all before you start.

 There is a small chance that there is a small (internal) leak from the solenoid valve on the top, but think it is much more likely a piece of crud is stuck in the valve, disassemble, inspect and install new O rings. Cost would be the cost of the O rings, but if you have a good supplier, then less than $20 would be my guess.

Follow Mecho's testing to make sure it isn't some other valve backfeeding into this one.

edit:

If your a gambling man, leave the valve in place, don't mess with the top 1/2 and only take the snap ring off the outlet, and remove and replace the O rings that come out the bottom, clean the valve seat where the delivery valve seats. That is the most likely point of failure. Just two O rings.

the parts break down will not list the rubber diaphragm separate since it is part of the inlet/exhaust valve #6. thanks for the parts break down also.