SAFETY ALERT
If you have an older coach, like we do, the condition of the diaphragm is probably questionable. I found both of ours are cracked and in need of repair. The OEM part N15759DG is no longer available. The replacement P/N is 90555399.
From what I can tell you will never know this part is bad until the day you really need it :o
https://www.haldex.com/globalassets/north-america/documents/suspension-controls/l55297w
Bob
I used these. Cheap as chips, work fine:
PRESSURE PROTECTION VALVE - 1/4" NPT - REPLACES KN31000 9054107 842234136687... (https://www.ebay.com/itm/PRESSURE-PROTECTION-VALVE-1-4-NPT-REPLACES-KN31000-9054107-/252089683852?hash=item3ab1b74f8c)
Mine were both leaking bad too. Look close, I found a bunch of other leaks in the fittings in the tanks. Good time to fix. All small, but add up. The sealer gets old.
While you have tanks drained and all those fittings apart, might be worth changing these too.
Single Check Valve TRKN23000 (Compare to Haldex KN23000) | eBay (https://www.ebay.com/itm/Single-Check-Valve-TRKN23000-Compare-to-Haldex-KN23000/121432503900?epid=1630547171&hash=item1c45f0f65c:g:4NYAAOSwnDZUD2c~&vxp=mtr)
Bob, how did you find out they have gone bad??
JohnH
Mine started leaking.. order the ones above .. replaced yesterday .. both bad .. parts were cheap enough to replace and not fiddle with cleaning
John,
I had to take one apart to remove it.
Why did you have to take it apart to remove it?
Bob my question was about what happened to it that made you feel it's faulty?
John
jcus,
It was in the way of removing the front brakes check valve. FT did not leave enough
room to rotate that assembly without disassembling most of the parts.
Agree with that, had to disassemble mine piece by piece. As has been said, if going to all this trouble, might as well replace check valves as well as protection valves.
John,
Both of the valves were still functioning. The diaphragms are very thin and had substantial cracks all the way around.
I don't want to take a chance on a $15 part that is over 21 years old.
Bob
jcus,
The check valves I have are a two way check. It has a spool with a rubber cap on each end. The spool shuttles either direction depending on the air supply source. One spool was stuck.
Bob
Bob, some coaches have a single check valve before protection valve.
It is the round aluminum fitting. Maybe only on newer coaches.
Is there some DOT type reason not to insert a union at the base of the assembly to facilitate R&R? That sure would make things easier for future maintenance!
Don
It certainly would, but I think all fittings used in air brake system must be DOT approved. https://www.lawsonproducts.com/pdfs/PIRFP_AB_Hose_Tubing_Fittings_PI.pdf
Great to have all the part numbers and sources listed in this thread.
How many of each are required?
Is it only for the front?
THANKS!
It will depend on year and model of your coach. Best to look at your air schematic, or crawl under and look.
Mine has a protection and check valve on each dry tank, but yours may be different.