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LMTV air/brake problems

Oxyacetylene

Active member
Steel Soldiers Supporter
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Location
Stoneville, NC
Haven't found info on a rebuild kit for Wabco 461-315-161-0 treadle valve yet. Several local auto parts places and a big truck repair place don't find reference to any kit. The big-trucks guy speculated the treadle valve is critical enough that a new, certified, valve might be all that is available.

Anyway, I took apart the treadle valve again, cleaned again, and got it working fine. The guts look like new, o-rings pliable, and face seals just fine. I had just found a tiny pile of sand in there and one chunk caught in a face seal. That's what dumped my air.

Here are some notes if you suspect trouble with the treadle valve. First, the vent for it is in the center of the front of the truck, in front of the radiator, and you can reach it if you take off the grill and reach upward. It vents downward. But, reaching it won't help a bit!

Physically tracing the source of the hose to that 'leak' is impossible....can't to it, it's back behind the heater. Just know that that vent comes from the treadle valve. The hose to the vent comes off the treadle valve on it's rear, the side nearest the driver, and nearest to the steering column. The thin-walled vent hose is a press fit, and can be removed by hand. Pull the hose off and now the vent is right there under the steering column where you can hear it. If you heard air escaping up front, you will heard it there at the treadle valve.

This is where the swoosh of air comes from when the brakes are dumped.

A leak through the treadle manifests as air coming out that vent. As air flows there then air will be flowing through the brake controller on the dash. It can sound like the (yellow knobbed) control is leaking.

The leak can be on either of the two circuits, front or rear, and it can make a huge difference on repair effort as to which is leaking. My initial leak was on the rearward section and that is the tough one to work on, but it can be done without removal.

Testing which section is leaking: First, a numbering convention is needed. There are four tubes coming out the left side of the treadle valve. As you look at them from standing beside the drivers floorboard, I called them 1, 2, 3, 4, just as read from top left to lower right.

1 and 2 are input hoses and have truck air on them. If you remove the lower two, 3 and 4, those go to the brakes and have zero pressure if not actuated. If pressure is coming out of either of those hoses (hose side) it's feedback from the brake system, and something leaking elsewhere, not the treadle.

If there's air coming out of the ports 3 or 4 then the treadle valve is leaking. My initial failure was air leaking out of port 3 (caused by the gravel in the face seal). My second failure was leakage coming out of port 4, the other face valve leaking.

If your leak is out number 4 then removal of just the most accessible half of the treadle valve is required. Disconnect the pressure sensor, take out 4 bolts holding the two halves of the treadle valve together, and work it loose. Note o-ring seal.

Take apart this half of the assembly with retainer clip pliers, being ready for strong spring pressure(!!!). Disassemble, clean out junk, lube, and reassemble.

It's a good idea to remove both hoses 1 and 2, build truck air, and let those hoses blow all the crud out of the lines before reattaching everything.

That how I got my brakes going.
Be aware that the Park/Trailer valves also "VENT" out the same port behind the grill, in front of the radiator as the treadle valve.

View attachment 635440

OD
tennmogger, would you mind copy/pasting this to the thread below? If Overdrive doesn't mind, maybe add his pic in there too. This is a great bit of troubleshooting information. I had hoped to kind of consolidate some of the air system info into a single thread where appropriate. Worthwhile you think?
http://www.steelsoldiers.com/showthread.php?140345-Air-Brake-Info-and-Troubleshooting
 

RAJ LMTV

New member
49
1
0
Location
Texas
I got all of mine from NAPA. Took in the old ones and they cross referenced for me then ordered them. Took just a couple of days
 

Reworked LMTV

Expedition Campers Limited, LLC
Supporting Vendor
1,506
1,174
113
Location
TN
what was your cost?


I found all the parts I needed at 'find it parts . Com' (no joke)
i bought shuttle valves instead of diaphragm
part # kn25061 for the shuttle valve
part # RN31BC for the tractor protection valve repair kit
both are haldex parts
 

Pointman0853

Member
Steel Soldiers Supporter
319
13
18
Location
Gardnerville, NV
I have done a bit of research into the Wabco, now Meritor #461-315-161-0 treadle brake valve. New, they are hard to find and hella expensive. Northward of $500 large was my quote. No sign of a 're-build kit' of any kind. Might be a case of obvious product liability as previously stated.

I may just crack mine open and replace the o-rings. It leaks when cold, and more when really cold... it's quite annoying.

Pointman
 

Dave21

Member
31
2
8
Location
Las Vegas NV
Does anybody have a break schematic for an A1?
After stopping at a stop sign taking my foot off the pedal the brakes would not release . Waited about 5 minutes and then they released . This happened every time.I stepped on the brake.
if anyone has any suggestions could you let me know . I've heard this happening in Frozen climates do the moisture. Our current temperature is 100 degree's.
Thanks
 
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