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mike2wheels

Replacement parking brake valve

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This is on a 2006 HR Endeavor with a Cummins ISL.  I'm looking for a replacement for the push/pull parking/emergency brake valve, the valve on the other end of the yellow handle.  When I pull my yellow handle out I can hear air flowing through the valve.  I think after pulling the handle to apply the brakes the valve should be silent.  My valve has a label for a Meritor Wabco 9366490120.  However, the valves I've looked up with similar numbers don't look anything like mine.  I've found a Haldex KN20021 and Haldex KN20031 that look similar to my Meritor valve, but I don't know how interchangeable these valves are.  Anyone know if I can use anything with sufficient ports and a release pressure of about 35psi?  I'm thinking of getting 2 output ports so I have a port for the pressure sensor.

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16 hours ago, mike2wheels said:

This is on a 2006 HR Endeavor with a Cummins ISL.  I'm looking for a replacement for the push/pull parking/emergency brake valve, the valve on the other end of the yellow handle.  When I pull my yellow handle out I can hear air flowing through the valve.  I think after pulling the handle to apply the brakes the valve should be silent.  My valve has a label for a Meritor Wabco 9366490120.  However, the valves I've looked up with similar numbers don't look anything like mine.  I've found a Haldex KN20021 and Haldex KN20031 that look similar to my Meritor valve, but I don't know how interchangeable these valves are.  Anyone know if I can use anything with sufficient ports and a release pressure of about 35psi?  I'm thinking of getting 2 output ports so I have a port for the pressure sensor.

 I'm thinking of getting 2 output ports so I have a port for the pressure sensor. When the air pressure drops below around 50 psi an buzzer should sound!

Once the air drops below 40 /45 psi the park brake's will lock on AND you will STOP!!!

         Mike, when the park brake is applied all the air is released from the spring loaded portion of the rear brake cylinder. The spring then keeps the brakes applied until the required air pressure is in the cylinders to release the park brake. ALWAYS block the wheels when working on the park  or roiling brake lines.

Rich.

This link might help understand the difference and how the 2 air systems work. RV's and big trucks are very similar in many ways.

 https://www.google.com/search?rlz=1C1VFKB_enUS711US716&sxsrf=ACYBGNQc6d2MOkMSXOZ1PWnuk0SBJkoRag%3A1579115253521&ei=9WIfXsi3H9jKtQbb16XQBA&q=difference+between+primary+and+secondary+air+brake+air+lines&oq=difference+between+primary+and+secondary+air+brake+air+lines&gs_l=psy-ab.3..33i299.9639.22011..25704...0.2..0.155.1415.0j11......0....1..gws-wiz.......0i71j35i39j0i22i30j33i22i29i30j33i160.GHCAxTe1xfg&ved=0ahUKEwiIhvvdpobnAhVYZc0KHdtrCUoQ4dUDCAs&uact=5

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On 1/14/2020 at 8:21 PM, mike2wheels said:

This is on a 2006 HR Endeavor with a Cummins ISL.  I'm looking for a replacement for the push/pull parking/emergency brake valve, the valve on the other end of the yellow handle.  When I pull my yellow handle out I can hear air flowing through the valve.  I think after pulling the handle to apply the brakes the valve should be silent...

Has it always been this way or is this a recent change in how it sounds?

In my experience in trucks, every valve makes that sound when applying the parking brakes. As mentioned above, the whole purpose of the valve is to release the air from the spring brakes so that they apply.

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Once the brake is set, there should be no sound of air!  If there is, then you have a leak in your system and it may/or not be a valve...I had a broke L in my gauge, after finding and replacing the plastic L with a SS L, no more problems!

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Correct.  When engaging the parking brake, there should be a loud release of air  as the spring applied, air released brake applies, followed by zero air coming out of it.

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On 1/14/2020 at 9:21 PM, mike2wheels said:

When I pull my yellow handle out I can hear air flowing through the valve.

Air flowing through the valve or leaking out of the valve? 

Any issues with an air flow sound through the valve when you release the parking brake, any erratic gauge movement i.e. needle twitching that doesn't stabilize after a few seconds?

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I can attest to the fact that noises that sound like they are coming from that valve may actually becoming from other parts of the parking brake "system".  Because of a problem that I don't need to bore everyone here with, I had multiple opportunities to have my airbrake valve make noises like it was leaking, when, in fact, the problem was a leak at the air actuator that applies and releases the brake!  The OP's problem most likely has nothing to do with mine, but I simply wanted to caution not to assume that the valve was the source of the problem.  I, too, replaced my brake valve to no avail.

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Docj may have been closer to the problem than any of us.  The problem was the valve had a sound of escaping air after it had been set, a continuous hiss.  It was very faint; I used a leak detector to amplify it.  And it showed no bubbles when sprayed with soapy solution.   I replaced the valve with a Haldex KN20031.  Although the new valve does not have a continuous hissing sound, there is still a leak somewhere.  The system (both needles) loses something less than 10 psi an hour.  I've been over the chassis from front to back with a leak detector and heard no leaks.  The original valve was failed or failing, but the problem is bigger than a new valve.

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What happens when you perform a standard air brake leak test, like you would for a pre-trip inspection?

If you lose air during that test, then the problem may not be in the parking brake system at all but rather in the service brakes.

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Air Brake System Pre-trip Check

 


1. Be on reasonably level ground.  Block wheels so the coach can not move even with the parking brake off.

 

2. Start engine and run until full air pressure is reached. Listen for the dryer to purge (about 120 PSI).


3. Shut off the engine.


4. Release the parking brake by pushing in the yellow button (make sure you don't roll, and do NOT apply the brake pedal).


5. After the initial pressure drop, the system should not loose more than 2 PSI per minute.


6. Apply the brake pedal firmly (still with the parking brake OFF).


7. After the initial pressure drop, the system should not loose any more than 3 PSI per minute.


8. With the engine off, ignition on and parking brake off, rapidly pump the brake pedal to bleed down the air supply. During this stage you should watch for the warning light and buzzer at about 60 PSI and then the yellow button (parking brake) should pop out at about 30 PSI.


9. Restart the engine and build up air pressure again. While building up pressure, check how long it takes for pressure to go from 85 to 100 PSI at “cruising RPM”. It should be less than 45 seconds.

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mike, docj's comments got me to thinking. Winnebago has all their schematics and diagrams for each model MH online. Hopefully your MH mfgr. does too.

There are multiple check valves in both the brake and suspension air systems. Perhaps there are one or more leaking backwards. My MH has developed the same hidden air pressure loss, and I am ignorant of how to find a leaking check valve; I too have spent several hours with a spray bottle filled with children's bubble soap underneath my MH and only discovered two very slow air leaks, like one- three bubbles a minute.

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I've run through the pre-trip check with no discrepancies. I don't notice any air loss during the short times used in the check.  How do you test for air loss in a valve?  I know you can spray the fittings and look for bubbles, but if the air is not escaping to the atmosphere I don't see how the valve can be tested without removing it.  There's a lot valves under there.  I've used soapy water to spray fittings; do you dilute the bubble soap or use it straight?

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Yup, soap/bubbles is the way to test any air fitting/device that could leak externally. Kiddie bubbles is best, but any soap that you "foam up" will work. Rinse them off when you are through.

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For internal leaks or bypassing/blockage issues you must understand how the valve is supposed to function to test it. 
Check for proper air input, Command it and disconnect the output is usually where I start. air out and it’s supposed to, move onto the next one. No air out when air is supposed to be present you found your problem. It sounds simple but can be frustrating, lines won’t disconnect, you think you understand the flow and your wrong, hang a valve them realize you missed something.

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The purge valve on the air dryer went bad (failed to close) was the most frustrating moments I have to remember. The leak was so great that the air governor failed to let air build. I had to find an external air compressor that would start the fill process before I could hear the dryer letting air escape. Air can certainly be frustrating to trouble shoot sometimes.

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Kay, I had one on the air dryer fail in the open position. Fortunately the the air governor kept it at about 70 psi and I made it to a Freighliner shop.   Yep, frightening

However I do know that if the air brakes engage while you are driving down the road it will not throw everything to the front. Depending on how fast you are going it could be a few hindered feet before the coach comes to a rolling stop. Mike at Gaffney Freighliner demonstrated it by pulling the "emergency" button at about 45 MPH. Bus just came to an easy rolling stop.

 

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12 hours ago, kaypsmith said:

Air can certainly be frustrating to trouble shoot sometimes.

Especially the type with the caged pin permanently installed in place, the air doesn't leak externally, it back feeds. 

 

10 hours ago, wayne77590 said:

Bus just came to an easy rolling stop.

Its not likely they would lock up under all of that weight. Unless tire friction is reduced.

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Well, I would expect that if one had to pull the emergency knob they would also be applying brake pedal pressure. Not a good thing, but definitely stop a coach quicker. Just an air leak to below 65+/- psi would be a slower rolling stop. Mike's demo was very good and informative - as is everything at Gaffney.

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Wayne, air drum brakes for my comment above, air disc there is a good chance they will lock. 

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10 hours ago, wayne77590 said:

Yes on discs.

Wayne,

Disk brakes on the rear (park brake is on the rear axle or driveshaft, not front)?

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