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Park Brake Valve Difficult to Release
My park brake valve is extremely difficult to release on a ’98 XL. Park set feels normal with a pop as it pulled up. Pushing it down is very difficult to release as if air pressure is forcing back up. Lots of air hissing. Is this a sign of a bad PP-2 park brake valve ? Or is it a more likely a sign that some other part down stream is leaking excessive pressure back to the PP-2 ? Like a park brake chamber with a leaking diaphragm or bad relay valve, etc. ?
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12 Replies
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The orings in the valve can get sticky. Squirt a little WD49 or similar at the shaft when it is up. Exercise ti several times, it may free up.
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Was told by a locksmith some years ago to NEVER use WD40. Because they intentionally put a varnish like substance in it so over time what was lubricated will start sticking again and like magic another shot of WD40 will free it up again (also adding a little more varnish like substance) starting the cycle all over again.
Since being told that I have paid more attention when using WD40 and it seams to be true. (Personal experience only, your results may vary).
Chuck
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I would pull it out and replace it. Keep the old one as a spare if you want to take it apart and look at it. This valve is the same as any other valve, internally there is a spool driven by the button you push and pull. When you have it apart you can verify the air signals via your air schematic on the Prevost Website.
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Consider using CorrosionX as the lube for the valve and locks. This product polar bonds with the bare metal in the device which not only lubes it but stops corrosion. Will not gunk up the device.
Polar bonding and corrosion killing makes this product great for electrical connections, boards and switches. Good on anything up to 36,000 volts.
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Roger – replaced mine and afterward, pushing it down was amazingly effortless – and, has remained effortless for about 2 years.
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Just had mine replaced. Same story as yours. It was stiff to operate and leaked alot of air when doing so.
Now it’s smooth as silk and easy to operate.
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Thanks for all the feedback. It sounds like all your issues were confined to the park brake valve itself. Not something downstream. I ordered a replacement valve & will let you all know the results.
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When brake tank pressure drops below 60 psi the PP-2 knob pops up and spring brakes engage/take over. You can try to push it down but comes back up.
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Be very careful to mark the lines if they are not already. On my bus there was not much room to work which made it doable but slightly challenging.
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I finally replaced the park brake valve. Its perfect. Push or pull with ease. Almost feels like it pops into position. Great fix. Found a huge air leak on the tag lift valve supply line. Replaced all the push in fittings to DOT compression style and both valves are sealed up.
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Well done Roger!
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Excellent!
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