m923a2 not airing up

[winterton1]

Well if the cotton valve from the treadle valve is still leaking then it is a faulty valve.

i'll get another one and give it a try.

 

[winterton1]

i'll get another one and give it a try.

OK. some progress. i replace the new bad treadle valve with a new one and it stopped the venting of air to the stack from the cotton covered line. truck came up to pressure and releace the spring brakes. i did have a small leak from a misaligned spring brake diaphragm but got leak to stop. i move the truck forward a few feet and the sping brakes work but when i step on the brake pedal i have air rushing out of the same cottont line to the stack??? any ideas

 

[winterton1]

OK. some progress. i replace the new bad treadle valve with a new one and it stopped the venting of air to the stack from the cotton covered line. truck came up to pressure and releace the spring brakes. i did have a small leak from a misaligned spring brake diaphragm but got leak to stop. i move the truck forward a few feet and the sping brakes work but when i step on the brake pedal i have air rushing out of the same cottont line to the stack??? any ideas

forgot to mention...now the abs light is staying on as well?

 

[simp5782]

You said you replaced all the service and spring brake diaphragms in the rear?

A bad one can cause it to vent to the intake.
You need to narrow down which axle. Go to the rear most axle. You should have a port on the brake relay valve that says EXH. Remove it. See if you have air there when you hit the brake over the intake

 

[winterton1]

You said you replaced all the service and spring brake diaphragms in the rear?

A bad one can cause it to vent to the intake.
You need to narrow down which axle. Go to the rear most axle. You should have a port on the brake relay valve that says EXH. Remove it. See if you have air there when you hit the brake over the intake

ok - here is a pick of the rear axlw valve. been paint and cant read EXH - which of the lines is the exhaust?

 

[simp5782]

I forget its an ABS truck so the vent won't go to the relay valve.

so On top of the axle. You should have a tree like below. The one that has the big lines that has the white nylon plastic lines below it is the one you want to remove. scrape the paint off the lines to show which one is white. Sometimes its the rear one circled.

 

[winterton1]

I forget its an ABS truck so the vent won't go to the relay valve.

so On top of the axle. You should have a tree like below. The one that has the big lines that has the white nylon plastic lines below it is the one you want to remove. scrape the paint off the lines to show which one is white. Sometimes its the rear one circled.

Found the problem..you were right again.. i had a misaligned service brake diaphragm on the rear axle. Truck is fixed and took it for a test drive. thank you and all that helped. i learned a lot.

 

[winterton1]

trucks been working great. now have a air leak from a valve above the rear axle?? bleeds out over night now. was wondering what it is anda part # if it needs to be replaced?

 

[simp5782]

trucks been working great. now have a air leak from a valve above the rear axle?? bleeds out over night now. was wondering what it is anda part # if it needs to be replaced?

Ctis safety valve

Valve , Safety Relief ; M939 5TON ; 4820-01-276-5731 , 12378688 , 599802

Valve , Safety Relief ; M939 5TON ; 4820-01-276-5731 , 12378688 , 599802

www.arnasmsl.com

 

[winterton1]

Ctis safety valve

Valve , Safety Relief ; M939 5TON ; 4820-01-276-5731 , 12378688 , 599802

Valve , Safety Relief ; M939 5TON ; 4820-01-276-5731 , 12378688 , 599802

www.arnasmsl.com

thanks!

 

[Jbulach]

trucks been working great. now have a air leak from a valve above the rear axle?? bleeds out over night now. was wondering what it is anda part # if it needs to be replaced?

Quick release valve. Should not have air on it except when the the CTIS is airing up or down, unless you have a wheel vale leaking on that axle, but in any case air should not be coming out anywhere except the rubber duckbill vent on it View attachment 807213while the CTIS is airing down.

 

[winterton1]

Quick release valve. Should not have air on it except when the the CTIS is airing up or down, unless you have a wheel vale leaking on that axle, but in any case air should not be coming out anywhere except the rubber duckbill vent on it View attachment 807213while the CTIS is airing down.

does anyone have an NSN or aftermarket part # for this?

 

[Jbulach]

QR valves are fairly standard and common other than port size/thread. You may be able to take yours to a good NAPA or truck stop garage and match up the threads for a lot less $. Some people have also had luck taping threads into the unthreaded port on cheaper valves.