Brake application valve free play

richard5933 · August 09, 2021, 02:37:35 PM

Curious how much free play (if any) is considered normal between the brake pedal in its neutral position and when it first makes contact with the brake application valve. I've got maybe 3/16" travel and not sure what's considered normal. The free play appears to be between the upper plunger and the inner workings of the valve body, not between the pedal roller and the upper plunger.

Is this adjustable? Sign of a new application valve to come?

No leaks right now - just trying to stay ahead of any problems. Probably been there since I bought the bus four years ago but just now noticing it. I think.

buswarrior · August 10, 2021, 05:46:40 AM

Hmm, haven't heard that one before... i guess there's no drawing with a tolerance in da book?

I would be more worried about whether the valve reaches bottom/full application, and releases, than the space at the top.

And flex in the supporting/attaching pieces.

Happy coaching!
Buswarrior

richard5933 · August 10, 2021, 05:59:20 AM

Quote from: buswarrior on August 10, 2021, 05:46:40 AM
Hmm, haven't heard that one before... i guess there's no drawing with a tolerance in da book?

I would be more worried about whether the valve reaches bottom/full application, and releases, than the space at the top.

And flex in the supporting/attaching pieces.

Happy coaching!
Buswarrior

The free play seems to be within the upper rubber boot/plunger. When the pedal is depressed, the upper bit moves about 3/16" before engaging the other internal bits.

The pedal itself if firmly attached, and the floor around it is rock solid. Valve appears to be firmly mounted from below.

Brake function appears normal and pedal moves through complete range all the way to the lower stop bolt. No leaking that I can detect.

Not being really knowledgeable about the inner workings of the brake valve I wasn't sure if the free play is normal or an indication of bad things to come. From what I was able to explain to Luke he didn't think it was a problem, but I wanted to get opinions from others to see if anyone has seen something like this.

Like I said earlier, it's likely been there before and I'm just now noticing it. Had to vacuum out some crud around the pedal and that's when I realized the free play was there.

dtcerrato · August 10, 2021, 06:23:59 AM

Richard I'm wondering if the play you're feeling is in the swivel joint at the base of the pedal. When you mentioned vacuuming sand out of that area it rang that bell. My swivel joint had play in it & I depleted that play with copper shim stock then keep it lubricated & clean. I'm with Luke on no detriment in it's function.

richard5933 · August 10, 2021, 06:27:34 AM

Quote from: dtcerrato on August 10, 2021, 06:23:59 AM
Richard I'm wondering if the play you're feeling is in the swivel joint at the base of the pedal. When you mentioned vacuuming sand out of that area it rang that bell. My swivel joint had play in it & I depleted that play with copper shim stock then keep it lubricated & clean. I'm with Luke on no detriment in it's function.

That was a thought I had, but it appears that the roller on the bottom of the pedal is making good contact with the upper plunger. Whatever is going on is happening inside the upper boot.

dtcerrato · August 10, 2021, 09:08:44 AM

Quote from: richard5933 on August 10, 2021, 06:27:34 AM
That was a thought I had, but it appears that the roller on the bottom of the pedal is making good contact with the upper plunger. Whatever is going on is happening inside the upper boot.

I wasn't referring to the roller but the pivots at the base of the pedal itself - if there is looseness there it can be easily eliminated with shim stock.

richard5933 · August 10, 2021, 10:54:06 AM

Quote from: dtcerrato on August 10, 2021, 09:08:44 AM
I wasn't referring to the roller but the pivots at the base of the pedal itself - if there is looseness there it can be easily eliminated with shim stock.

Got it. Not that either. The upper pedal assembly has no free play at any of the pivot or mounting points. It's clearly in the top of the valve in the upper section.

chessie4905 · August 10, 2021, 09:37:05 PM

Thought there was a spec for that, either in the Coach manual, or in the Bendix component rebuild manual.

richard5933 · August 11, 2021, 02:54:48 AM

Quote from: chessie4905 on August 10, 2021, 09:37:05 PM
Thought there was a spec for that, either in the Coach manual, or in the Bendix component rebuild manual.

I didn't see one in the coach manual, and I don't have the Bendix manual. Is it available online?

chessie4905 · August 11, 2021, 06:58:18 AM

Should be still out there

richard5933 · August 11, 2021, 07:29:58 AM

Quote from: chessie4905 on August 11, 2021, 06:58:18 AM
Should be still out there

Any thoughts on what the manual is called? I just checked the Bendix site and there are LOTS of manuals.

Is it specific to the particular valve? In this case I guess I need to find out what valve I have in there.

Or are there generalized rebuild manuals?

I'm sure I could find it online if I knew what I was looking for.

chessie4905 · August 11, 2021, 03:40:06 PM

not sure. out on the road this summer. manuals at home.
maybe bending component rebuild manual