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R 14 module/ Park brake valve
Does anyone know the function of the R 14 module? The one on my drive axle brakes releases all the air when I shut down the engine. It never did this before I had all the issue with the pressure problems. Is there a drawing of the air flow through the valve and specs on how it functions? One more thing, I haven’t got to the air suspension system yet but where does it tie into the air system? Thanks a bunch! : )
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9 Replies
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The R14 valve is a relay valve and a quick release valve with anti-compounding.
The valve receives a pneumatic signal from the brake treadle and proportionately delivers air pressure from an air tank direct to the brake chamber. When you lift your foot from the brake treadle the valve is a quick release which dumps the air pressure that has applied the service brakes.
The anti compounding means you cannot apply both emergency brake pressure and pneumatic pressure from the service brake sumultaneously exerting a force that might be excessive.
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Thanks Jon! You are an expert and I appreciate that great description of what the vakve does. Do you know if the valves also dumps all the air when the you shut down the engine? I am trying to find out if I need to replace it. Thanks!
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When you shut off your engine I am not aware of any air escaping from the chassis systems or any systems installed by a converter.
If you lose air when the key is off you have a leak and something that needs to be repaired. Specifically your coach should hold primary and secondary air system pressure for a long time. I’m talking months. Those are your brake systems and with the parking brake engaged and your foot off the service brake all brake system air is locked into the air tanks at the relay valves and there is no air pressure at the brake chambers.
The auxiliary air system is another story. It is complex with a lot of fittings and valves and devices so it is likely to leak unless you have the time and patience to make it leak free. Anyone here on these forums would be happy if their aux system was so tight it retained pressure for a day.
The suspension system is shut off when the key is off meaning air is locked in it. Unless it has leaks the bus will not drop or lean for days or weeks or months. Even if all air is exhausted from the other air systems the suspension should keep the bus up because when the key is off the valves to the suspension are closed.
If you hear air escape when you shut the bus down, unless it indicates the purge cycle from the air dryer, there is sonething wrong and it should be corrected.
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Ok, It is definitely not the air dryer purging then. I will replace the R 14 module and see if that corrects the air release between the Drive and tag axle. My coach has never kept the suspension aired up more that 30 minutes after shutting the engine down but now it will not even air the suspension system up.
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Having recently replaced this valve, due to it puking air, although only when the engine was running, I think that your issue may be elsewhere. Take a close look and listen for the air leaks and report back,
Best
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Take the small line off top and see if it stops. That is the only thing that tells that valve to operate. The only way air should be comming out the service brake R-14 is releasing air after the brakes cans are released after application. FWIW.
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Thanks Bob and John! Will do! John … do you remember what the cost of the valve was?
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Mike,
Relay valves are pretty cheap available at truck supply stores.
What everyone needs to understand is if you have a substantial leak in the primary or secondary brake system no air or insufficient air is going to go to the suspension system because the brake system needs to have about 75 PSI before air will be admitted to the aux air system.
What Bob is correctly pointing out is that your relay valve gets the air signal to operate from the foot treadle. The foot treadle does not deliver air to the brake chambers, but instead delivers air to the relay valve which opens a path between the air tank and the brake chamber. When you remove the air line that delivers air from the foot treadle from the relay valve you should not hear and air escaping from that air line or the relay valve. To test it keep shop air connected to the coach regulated to 120 PSI or less.
If air escapes from the small air line, look to the foot treadle as the problem. If air escapes from the relay valve, that is your problem.
Bob is a hands on guy with a good understanding of coaches. Pay attention to his advice.
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Thanks for the advice!! I will check the valve out.
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