Braking Issues

SmallPackage · Dec 29, 2019

Great to hear!
I am going to add this to a troubleshooting “weird non- text book” shop book that I put together decades ago for things like this. The problem sounded like a one in a million kind of thing for a valve to cause it. Really made you work hard for it.
I learned from this too.

MX127 · Dec 29, 2019

MX127 said: ↑

Installed new spring brake chamber and R-12 valve, problem solved.

Do to the fact the last drive axle has the parking brakes and was sensitive to locking up during braking, I believe a failed piston seal was the cause. The piston seal is designed to separate the two air chambers, both service spring and parking spring preventing them from compounding.

Though I can not 100% rule that out because both parts, the R-12 and brake chamber were replaced simultaneously, if faulty either one can cause the same issue.

Because the first drive was less susceptible to locking up under braking, reasonably deducting, I believe the R12 did not fail (I am going to open and inspect it soon).

Only one set of air lines tied into the R12 valve supplies both axles. That set of lines later split "T" off supplying the rear axle chambers by two additional air lines. I found this unusual that both axles were not supplied by two separate sets of air lines directly from the R12 valve. Understanding the first axle performed well, ruled out the possibility of the R12 failing. The only difference between the two axles was the parking breaks on the second axle.

Therefore I believe brake compounding was caused due to a failed chamber piston seal. As a failed seal causes air loss, leading to both left and right rear axle wheels becoming sensitive to brake skidding. Both parking brake springs are connected to one parking brake valve, both lose air simultaneously, internally leaking into the service brakes (like a failed double check valve) inturn multiplying force against the slacks by compounding both service and parking brake springs. No air leaks were detected.

Never the less, problem solved. I can return the treadle valve for a refund.

I cannot thank you all enough for your knowledgeable understanding and willingness to help me. Your information and experience is priceless and I value each and everyone of you from the bottom of my heart!!

God bless you all in Jesus name =)
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Identifying and Understanding Brake Chambers:

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