I'm going to throw this out and see if anybody has had this issue.
We have a 50 ton GE with 14el brake system. For the past 5 years I have worked out many issues with this old girl, but I have one that still eludes me. The equalizing res. pressure tends to climb over time, especially after blowing the horn for a crossing. It seems to start when the main res drops down below the compressor cut in point. Reduce the brake pipe below the set point, release it and your good to go for a while. Both reducing valves have been changed, the k14 brake valve and the distribution valve, all with new gaskets of course. Nothing has seemed to change it. I even adjusted the cut in/cut out points for the compressors. No change. Everything else works as it should.
Any thoughts
E.

Are you running a 6K distributing valve, or a 6N?

Have you sent ALL you brake valves to a brake shop were they could each be gone through and tested ?

I did a complete set of 14EL a few years ago, set them to a shop and they did not work right when they came back, but they corrected the problem.
The automatic would not work properly and it went to another Wabco shop, which found out that the first shop did not completely assembly the automatic properly.

I had to send them a couple of extra M3 feed valves, as they said the first ones I sent would not hold air properly.

These older valves use babbitt on slide valves. Once that becomes too worn, most shops can not repair them.

A very small leak some place can also really mess with you on a brake system. I recently fought a 26NL system, trying to get it to work properly in the dead in tow position. Changed one valve and it quit.

All of our valves have been sent in every two years. This issue has remained with two completely different sets of valves (we have two sets so we can send one in to be certified without being out of service. Then we just swap them out.)

I will have to double check, but I believe we have the 6K.

If the valves have all been changed, I think I would start looking for a crack in a pipe bracket that could let air cross over from one port to another.

Suggest that you check the nuts holding the K14 to the bracket. They need to be reasonably tight, to approximately equal torque with one another. We once had a similar problem with the 14-EL that was caused by a slightly loose K14, allowing M.R. air to go places that it shouldn't.

JR

You just mention the equalizing reservoir pressure creeping up but is the brake pipe doing so as well? Does this occur in running position or lap?

Check the dead engine cut out valve and the check valve in the strainer. If these are leaking it will allow main reservoir pressure to leak into the brake pipe.

You could also check to see if the mounting bolts are stretched so the pitch varies over the length of the threads. If they are, the nuts can be tightened, but they may not be clamping the gasket tightly.

The first time I removed the k14, I replaced all the studs because the threads were so bad. I would be shocked if the issue was in that gasket area.

This issue starts in the equalizing resevoir, which the brake pipe then mimics. It only does it in the running position. Lap holds perfectly. What we noticed is if you don't catch it, the pressure will rise to about 10-15psi lower than the main resevoir pressure, but will not rise any higher. If you blow the horn, or apply the independent, the brake pipe pressure will not drop until the main resevoir drops lower than the brake pipe.

It sounds like the feed valve.

This is a fairly common problem with M3 feed valves, the slide valve seats will not maintain the seal. As a test disassemble the valve and add 2 drops of compressor oil to the seat, and reassemble, if the problem goes away, you have found the problem. This is only a test, not a remedy. The remedy requires refacing both surfaces of the seat.
My 2 cents,
Mike Tillger

The feed valve was my first thought. I have installed 5 different feed valves. 4 have been certified, 1 I grabbed off a dead unit just as a shot in the dark. All have acted the same.

After looking at the brake schematic again, I am going to look closer at the dead engine cutout system (thanks Russ). I have never touched this valve, and truthfully don't even know where it is located. I can see where a leaking valve here would definitely cause the problem we are having.

Thanks for all the suggestions. All my local help deals with 26 and 24 mu systems only.

I recently had a similar experience and only after the sixth certified feed valve were we successful. They may pass muster if they are fresh from overhaul, but let them sit on a shelf for a few months (years in my case) and they may or may not function correctly. Russ's suggestion is a good one, and definitely worth checking out. Dead engine is typically located close by the distributing valve. There should be a cutout valve in addition to a differential check valve, strainer, and choke and it should only be in the open position if you lose your source of main reservoir. Good luck and please post your findings.
Mike Tillger

Very good idea on the Dead Engine Feature.

Another consideration: As-built, the check valve should be plumbed in a way that makes it impossible to get backwards. However, we got an 80 tonner that had been through a complete heavy rebuild for the military, and the piping had been changed such that the check valve could be installed in either direction ! And, it had been put in backwards on this loco before we got it. So if the cutout happened to be open, it would permit M.R. air to enter the brake line, which could get exciting with a heavy train. So, be sure that the arrow on the check valve points towards the Main Reservoir line.

JR

The dead engine check valve and strainer should be done with the other brake valves. On my recent problem with a 26NL brake and getting it to work in the "Dead in Tow" position, this was plugged. The company that I purchased the locomotive from had just, with in 6 months changed out the brake valves. They never touch the strainer/check valve. When not in use, it works like a trap. The strainer/check valve was plugged solid and I also had to remove part of the piping to clean it as well.