Parking brake release ( or not)

Parking brake release ( or not) - Printable Version

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Parking brake release ( or not) - Guy - 11-17-2019

Had a new parking brake valve installed last week to replace one that had a large leak. The new valve often fails to release, acting as if there is not enough air pressure. After a few tries, it will release. At the time I had the valve replaced, the brakes were also adjusted. Wondering if the two changes are related. It might just be my imagination, but it seems as though there is a lot of resistance to finally get the coach rolling after the valve does actuate.

RE: Parking brake release ( or not) - Richard - 11-17-2019

When you say fails to release do you mean it doesnt send a whoosh of air OR the coach doesnt roll freely? Either way have this looked after. Dragging brakes can result in a fire

RE: Parking brake release ( or not) - Guy - 11-17-2019

Richard, the parking brake air valve will not stay when pushed in to release the brakes. It reacts as if there is not sufficient brake air, but I have 120 lbs. After several attempts , it will release and stay in the released position. I was concerned about a wheel having a dragging brake, but I shot them with the ir gun after driving a few miles and all is well. It does feel as though there is initial resistance after being parked.

RE: Parking brake release ( or not) - Richard - 11-18-2019

Hmmm, as you already know, that should not be happening with the P brake valve. Either it is defective, or something is interfering with the handle going completely in. Take a quick look to make sure the locking nut that holds the stem of the valve is not interfering with the motion of the handle.

Glad you checked the temp!!!!

RE: Parking brake release ( or not - kaptain - 03-30-2023

(11-17-2019, 07:00 PM)Guy Wrote: Richard, the parking brake air valve will not stay when pushed in to release the brakes. It reacts as if there is not sufficient brake air, but I have 120 lbs. After several attempts , it will release and stay in the released position. I was concerned about a wheel having a dragging brake, but I shot them with the ir gun after driving a few miles and all is well. It does feel as though there is initial resistance after being parked.

I have a similar problem with my parking brake, described below.

1) Start the engine, and wait until air pressure reaches about 115 psi. Then I push the yellow “Parking Brake” in. But no matter how forcefully I push the knob, it simply won’t go in, and the “EMERG BRAKE” light remains on.

2) If I turn and twist the knob left and right while pushing hard, it starts to go in a little bit (a hissing sound can now be heard). Continue twisting and pushing. I can occasionally get the “EMERG BRAKE” light to go off.

3) sometimes, I am not that lucky getting the brake released, so I continue twisting left and right while pushing while doing this, I can see the air pressure start to drop, and it goes down and stabilizes around 75 psi. I understand the brake won’t release at this low pressure, so I pull out the knob and let the air pressure rebuild to about 115.

4) Some other times, I push and twist until the "EMERG BRAKE" light goes off. To ensure it's fully pushed in, I push it again and harder, then the ""EMERG BRAKE" goes back on again.

5) If I do eventually get the brake finally released, pulling out the knob is easy. And this set the "EMERG BRAKE" light back on.

6) Last year, when I had my 701 at the Cat repair shop, I requested to check and fix this problem. But the tech didn’t do anything about it, yet charged 3 hours of labor for “looking at the parking brake”. When I questioned this billing, the shop admitted 3 hours of looking without doing anything about it is excessive, so the labor for this part is reduced to 1.5 hours.

Now my questions are:
A) Does this appear to be the problem with the parking release valve or something else?
B) what is the part number of the parking release valve, and where can I purchase it (besides Newell)?
C) What other components in the brake system could cause difficulty in releasing the parking brake when air pressure is at 115 psi?

RE: Parking brake release ( or not) - Richard - 03-31-2023

First of all.

Contort yourself so that you can see the backside of this valve. It is possible that the nut which secures the assembly to the console is loose. So when you try to push it in, the slack in the mount allows the knob to hit the console instead of pushing in far enough to engage. When you pull it out, this is not a problem.

Easy diagnosis would be to put one hand on the back of the switch assembly and push the knob in with the other hand. You shouldn’t detect any back and forth movement.

The loose nut issue HAS been an issue on other Newells of this era.

If you need a new switch. https://www.napaonline.com/en/p/MBIKN20021?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Towing&campaign_id=8911645606&adgroup_id=106416389246&adtype=pla&gclid=Cj0KCQjwiZqhBhCJARIsACHHEH97PBwoz3p7JuJT6Pashhh8XE_zDSgnINRX-ppBulxiyvqFwa_HTHsaAi_vEALw_wcB&gclsrc=aw.ds&

RE: Parking brake release ( or not) - kaptain - 03-31-2023

(03-31-2023, 05:07 AM)Richard Wrote: First of all.

Contort yourself so that you can see the backside of this valve. It is possible that the nut which secures the assembly to the console is loose. So when you try to push it in, the slack in the mount allows the knob to hit the console instead of pushing in far enough to engage. When you pull it out, this is not a problem.

Easy diagnosis would be to put one hand on the back of the switch assembly and push the knob in with the other hand. You shouldn’t detect any back and forth movement.

The loose nut issue HAS been an issue on other Newells of this era.

If you need a new switch. https://www.napaonline.com/en/p/MBIKN20021?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Towing&campaign_id=8911645606&adgroup_id=106416389246&adtype=pla&gclid=Cj0KCQjwiZqhBhCJARIsACHHEH97PBwoz3p7JuJT6Pashhh8XE_zDSgnINRX-ppBulxiyvqFwa_HTHsaAi_vEALw_wcB&gclsrc=aw.ds&

Good point. Thank you very much, Richard.
It does look like the push-pull valve's metal mount lacks solid support (see photo).
Once pushed hard to release, the yellow knob (almost? or already?) reaches the leather panel.
As for the replacement part for this valve, the one shown in Richard's link appears made of plastic, but the existing one in my #701 is made of metal.

Because the yellow knob says "Bendix", I am trying to figure out which Bendix valve it is

RE: Parking brake release ( or not) - Richard - 03-31-2023

Yeah I was just trying to get you in the ballpark. Best thing you can do is take the valve out, after labels and pictures of course, and take it to NAPA or any truck parts place.

The mounting place looks bent to me in those pictures. All of them are relatively hard to push in and release on purpose.

Looks like Newell added an extension to the push rod to make it work in that location.

RE: Parking brake release ( or not) - kaptain - 04-03-2023

(03-31-2023, 01:34 PM)Richard Wrote: Yeah I was just trying to get you in the ballpark. Best thing you can do is take the valve out, after labels and pictures of course, and take it to NAPA or any truck parts place.

The mounting place looks bent to me in those pictures. All of them are relatively hard to push in and release on purpose.

Looks like Newell added an extension to the push rod to make it work in that location.

Good observation! Thank you, Richard.

I end up buying this one:
https://www.finditparts.com/products/2222674/bendix-275175n

Napa's website also listed the same product, but they don't have it in stock.
https://www.napaonline.com/en/p/TWD275175N

https://www.napaonline.com/en/p/TWD275175N

RE: Parking brake release ( or not) - Guy - 04-03-2023

Curious as to why the markings on the new push pull state "not a parking brake" ?