Driving 70mph down I10 the other day and the parking brakes engage. Makes for an oh no moment. Fortunately I was in the geezer lane and was able to pull to the shoulder quickly because those brakes slowed the bus really fast.
The parking brake knob was still pressed in, and my air gauges showed 100psi on front and rear. I reset and got the brakes released and drove on home. Now, it takes 4 or 5 tries to get the brake released.
Where can I find this valve? Apparently the Bendix PP1 valve number 287515 is replaced by something else. The local parts guy offered a Haldex valve, but it was all plastic. I passed on that.
From the tag it looks like the valve should release the park brake above 60 psi. I guess that is what that pressure means.
I know the parking brake engages at some point of diminished pressure, but I believe that is part of the eagle plumbing that allows that to happen.
I confess I am not well schooled in the operation of the brake system safety features other than it has always worked flawlessly until 2 days ago.
Any suggestions?
Thanks David
Quote from: David Anderson on February 04, 2021, 11:00:08 AM
Driving 70mph down I10 the other day and the parking brakes engage. Makes for an oh no moment. Fortunately I was in the geezer lane and was able to pull to the shoulder quickly. The parking brake knob was still pressed in, and my air gauges showed 100psi on front and rear. I reset and got the brakes released and drove on home. Now, it takes 4 or 5 tries to get the brake released.
Where can I find this valve? Apparently the Bendix PP1 valve number 287515 is replaced by something else. The local parts guy offered a Haldex valve, but it was all plastic. I passed on that.
From the tag it looks like the valve should release the park brake above 60 psi. I guess that is what that pressure means.
Any suggestions?
Thanks David
Call Luke at US Coach in NJ at 856-794-3104. He's going to have the current replacement for this valve and should still be able to get it out in today's mail. He's typically in until about 4pm EST Mon-Thu.
While you are at it, you'd betterdo some testing of the low air warning devic in all the places your coach has them.
What year? Is this brake system stock, or been converted?
Sudden application of the parking brake, without driver intervention, and the control knb was still in position?
Very suspicious, i would be, that this bus was trying to kill me...
Prove it out to be fit.
Happy coaching!
Buswarrior
Almost the same happened to me, except the knob actually popped out. Very lucky, my brakes weren't adjusted, and the s60 literally didn't know the brakes were on
I just got a new valve from the local truck shop, but then again I have replumbed some things after someone hacked spring brakes on, which eliminated the need for 100 psi foot application to release
Quote from: buswarrior on February 04, 2021, 11:47:03 AM
While you are at it, you'd betterdo some testing of the low air warning devic in all the places your coach has them...
Buswarrior
Like he said - have you done a brake leak test with a pump down recently? Great time to remind everyone, especially new bus owners, that brakes should be checked at the beginning of every travel day for proper function, including the low-air warning light and buzzer and that the e-brake automatically applies when the pressure drops.
Quote from: richard5933 on February 04, 2021, 12:46:26 PM
Like he said - have you done a brake leak test with a pump down recently? Great time to remind everyone, especially new bus owners, that brakes should be checked at the beginning of every travel day for proper function, including the low-air warning light and buzzer and that the e-brake automatically applies when the pressure drops.
I did a leak test with a pump down when I got home. Worked fine. Low air warning worked. Light worked. E-brake automatically applied on dropped pressure. Everything worked as it should.
Air system had never been hacked since I bought this bus when Houston Metro retired the fleet. It's all stock, but like all of us, things are getting old. :o
Quote from: David Anderson on February 04, 2021, 01:16:01 PM
I did a leak test with a pump down when I got home. Worked fine. Low air warning worked. Light worked. E-brake automatically applied on dropped pressure. Everything worked as it should.
Air system had never been hacked since I bought this bus when Houston Metro retired the fleet. It's all stock, but like all of us, things are getting old. :o
Good job running through all those steps. Does sound like the valve might be in need of replacement. Luke would be my first phone call if I needed one.
David check the rear chambers for a leak the Eagles aired the chambers up like a 1 time charge of air.I doubt it is your PV that is bad .the chambers do rust and you probably need new chambers but they are cheap and easy to find at any truck supply
Quote from: luvrbus on February 04, 2021, 07:28:10 PM
David check the rear chambers for a leak the Eagles aired the chambers up like a 1 time charge of air.I doubt it is your PV that is bad .the chambers do rust and you probably need new chambers but they are cheap and easy to find at any truck supply
How would leaking rear chambers cause the parking brakes to apply if there is still 100 psi in the system? Or make them difficult to release? Not sure how the mechanism works to produce those results.
Spring brakes takes air pressure to release where DD-3 brakes exhausts the air to release the chamber on spring brakes the chamber is charged one time any small leak they will set unless it has been plumbed for constant air supply which Eagle and others didn't always do ,David has owned his bus for a long I am surprised he still has the original brake chambers in working order.His metro Eagle should have spring brakes but could have DD-3's if he has DD-3 it is a easy change over to spring brakes on a Eagle
Quote from: luvrbus on February 05, 2021, 03:26:50 AM
Spring brakes takes air pressure to release where DD-3 brakes exhausts the air to release the chamber on spring brakes the chamber is charged one time any small leak they will set unless it has been plumbed for constant air supply which Eagle and others didn't always do ,David has owned his bus for a long I am surprised he still has the original brake chambers in working order.His metro Eagle should have spring brakes but could have DD-3's if he has DD-3 it is a easy change over to spring brakes on a Eagle
I get that, but where in the system is the decision made to apply the spring brakes in an emergency? At the cans or at the parking braking valve? Unless that decision point is at the cans how would leaking cans cause the parking valve to self-apply?
Quote from: richard5933 on February 05, 2021, 03:31:57 AM
I get that, but where in the system is the decision made to apply the spring brakes in an emergency? At the cans or at the parking braking valve? Unless that decision point is at the cans how would leaking cans cause the parking valve to self-apply?
He didn't say the PV self applied ,he reset the parking brakes filling the chambers again and rode into the sunset.he is probably going to need new chambers and they are not exspensive around 100 bucks each for MGM spring brakes
Quote from: luvrbus on February 05, 2021, 03:40:38 AM
He didn't say the PV self applied ,he reset the parking brakes filling the chambers again and rode into the sunset.he is probably going to need new chambers and they are not exspensive around 100 bucks each for MGM spring brakes
Sounded like what he said to me, "Driving 70mph down I10 the other day and the parking brakes engage. Makes for an oh no moment."
The brakes self-applied. The question I'm asking is can that happen without involving the parking valve? If spring brakes can self-apply if the can develops a leak, wouldn't that mean that it's also necessary to check out all the plumbing to confirm that there isn't a leak somewhere else in the system as well?
Spring brakes have a built in 1 way flapper to prevent back flow
Quote from: richard5933 on February 05, 2021, 04:17:23 AM
Sounded like what he said to me, "Driving 70mph down I10 the other day and the parking brakes engage. Makes for an oh no moment."
The brakes self-applied. The question I'm asking is can that happen without involving the parking valve? If spring brakes can self-apply if the can develops a leak, wouldn't that mean that it's also necessary to check out all the plumbing to confirm that there isn't a leak somewhere else in the system as well?
Yes, you are reading me correctly. Driving 70 the parking brakes applied, but the knob was still in the release (off) position. It was not popped out. What puzzled me thereafter is how many times it took to release the parking brake after I drove 2 more hours and was in my driveway trying to put the coach in the barn. That made me think it was the pp1 valve, but now with what Clifford said, I don't know :-[
David
Let's change gears here for a minute. With what I just posted above. It has always taken me at least 2 tries, sometimes a 3rd try to get the parking brake released. I would make a hard press on the E6 footbrake, pull the parking brake knob out and walla, no release. Try a repeat and walla, no release. Pump the E6 a couple of pumps and hold, walla, parking brake releases and on my way.
It has always been like this since 2001. That has always annoyed me, but I figured it always works so I move on.
I've seen other coaches that don't have to do that. One pull of the knob and away you go.
This is why I was thinking my PP1 valve my be going bad. I'm sort of guessing, however.
David
Don't you push the knob to release the park brakes? Or is it backwards on Eagle buses?
Hang on...
There were Eagles that were plumbed with valving that required a strong service brake application, to release a spring brake parking system.
If that bit of trickery is not functioning correctly, that may be the story.
Spring chambers can most certainly self apply, if there isn't somewhere over 60 lbs of air right there in them, never mind what is anywhere else in the system, the big spring starts squeezing out.
A local leak of sufficient size can cause this to happen.
My bet at this moment is the first suspicion. Confirm or deny the parking brake plumbing on that coach.
Maybe a pp4 was the device? I'm trying to remember which old busnut had it, and he sent me the schematic, back when i used to be intelligent... Shepard perhaps?
Happy coaching!
Buswarrior
Quote from: buswarrior on February 05, 2021, 09:18:38 AM
Hang on...
There were Eagles that were plumbed with valving that required a strong service brake application, to release a spring brake parking system.
If that bit of trickery is not functioning correctly, that may be the story.
Spring chambers can most certainly self apply, if there isn't somewhere over 60 lbs of air right there in them, never mind what is anywhere else in the system, the big spring starts squeezing out.
A local leak of sufficient size can cause this to happen.
My bet at this moment is the first suspicion. Confirm or deny the parking brake plumbing on that coach.
Maybe a pp4 was the device? I'm trying to remember which old busnut had it, and he sent me the schematic, back when i used to be intelligent... Shepard perhaps?
Happy coaching!
Buswarrior
Not applying a strong enough service brake application might explain why it's been difficult for him to release the parking brakes, but it doesn't explain how/why they self applied while traveling at 70mph with 100psi showing on the gauge.
So the air leaked out and let the spring brakes apply? (at 70) and when he reset the parking brake it put more air back in the chambers?
Jim
Quote from: Jim Blackwood on February 05, 2021, 09:34:26 AM
So the air leaked out and let the spring brakes apply? (at 70) and when he reset the parking brake it put more air back in the chambers?
Jim
The part that is still a mystery is why his gauge showed 100 psi while this was happening. If the pressure dropped low enough at the cans to apply the brakes it should have done so at the gauge as well.
Quote from: Jim Blackwood on February 05, 2021, 09:34:26 AM
So the air leaked out and let the spring brakes apply? (at 70) and when he reset the parking brake it put more air back in the chambers?
Jim
If this trick circuit is involved, and failing somehow, perhaps it is blocking the direct path from spring chamber to tank, which is supposed to be wide open, when the spring brake is released. Add in a leak at the chamber, blockage in the trick circuit, springs could apply while underway, and no control valve pop, since there's still pressure at the control valve, sufficient to keep it in the released position.
Richard, in a properly working spring brake system, if there was a steady leak, the bus will likely already be stopped before the parking control valve pops. The spring chambers start applying as the air pressure drops thru 60 lbs, the control valve won't pop until the pressure at the valve drops below 40, as low as 25 lbs, depending on the spring in the control valve. Dashboard readings are only acccurate for wherever the other end of the hose from the gauge is plumbed in.
Most everyone has not been properly taught these subtle differences, usually just the "fan the brake until the button pops" and assumptions that are wrong, go from there...
The springs were already applied before the button popped.
Happy coaching!
Buswarrior
Quote from: buswarrior on February 05, 2021, 11:19:35 AM
If this trick circuit is involved, and failing somehow, perhaps it is blocking the direct path from spring chamber to tank, which is supposed to be wide open, when the spring brake is released. Add in a leak at the chamber, blockage in the trick circuit, springs could apply while underway, and no control valve pop, since there's still pressure at the control valve, sufficient to keep it in the released position.
Richard, in a properly working spring brake system, if there was a steady leak, the bus will likely already be stopped before the parking control valve pops. The spring chambers start applying as the air pressure drops thru 60 lbs, the control valve won't pop until the pressure at the valve drops below 40, as low as 25 lbs, depending on the spring in the control valve. Dashboard readings are only acccurate for wherever the other end of the hose from the gauge is plumbed in.
Most everyone has not been properly taught these subtle differences, usually just the "fan the brake until the button pops" and assumptions that are wrong, go from there...
The springs were already applied before the button popped.
Happy coaching!
Buswarrior
Helpful clarification.
Sounds like there are at least a few points of inspection in order for this Eagle.
Sounds like there's an errant check valve some where in the brake system - fwiw
If he has a dual brake system, maybe gauge only has one needle instead of two. Maybe gauge is reading auxiliary system only because of incorrect plumbing.
Maybe the push-pull valve is defective.
That trick safety system, that requires a service brake application, to release a spring brake parking system, is a high probablity.
I wish i coukd remember who had the Eagle that was so equipped... municipal/regional transit background almost guarentees it is plumbed this way...
NIles, who is it that I can't remember has this Eagle similarly equipped?
Getting old is total crap... young people, make notes, your turn will come... my mother warned me... she was right... as the years pass, you won't remember $hit...
Happy coaching!
Buswarrior
Yes, I have the trick system. Jim Sheppard does too.
Both front and rear gauges showed 100psi when this happened. I agree that a harder longer E6 brake application may be needed to to release. I tried that a few times in the shop and it worked ok which pretty much eliminates a problem in the PP1 push valve (push to open).
Still puzzled about the errant spring brake application. If what Clifford said about the air charge is true, then most likely it is a leaking can. I am replacing the R8 parking brake valve and the spring brake cans. I'm not sure if the pawl is relaxed or under pressure when the parking brake is applied. The pins have to be removed to get the clevis to pass through the bracket as you remove the cans.
I removed the two front service brake cans. They both leaked on a held E6 application. They were easy to get out. I have them on the bench and new ones in hand ($41 each) and will replace them and the R8 valve and retest to see how things work.
Then I will get the big boys off and replace them. Ugh, it's hard working on my back under there.
David
BW wrong guy to ask your memory is better than mine for names/busses 😗
ya I remember I forgot something but I can't for the life of me remember what it was ???
dave
I got the 2 front brake cans and new hoses installed, readjusted the slacks back to Eagle book specs. Installed the new R8 parking brake valve and reinstalled the PP1 valve and knob on the dash. Checked all my work for leaks and found none
It is easier to release the parking brake, but I do need to give it about 2 more seconds of E6 footbrake to load the spring brake cans with air and it will release.
No more audible leak down under the coach with E6 pedal hold down. I held it down for 120 seconds and lost about 5psi on the gauges.
Oh and I determined the spring brake cans need to be loaded with air to relax the clevis to get the keeper rods out. I can then remove the can and slowly dump the air and let the threaded rod extend, then remove the air hose.
I will block the wheels and do this next week and replace both cans. I figure after 21 years, why not?
David
Quote from: David Anderson on February 06, 2021, 03:21:50 PM
I got the 2 front brake cans and new hoses installed, readjusted the slacks back to Eagle book specs. Installed the new R8 parking brake valve and reinstalled the PP1 valve and knob on the dash. Checked all my work for leaks and found none
It is easier to release the parking brake, but I do need to give it about 2 more seconds of E6 footbrake to load the spring brake cans with air and it will release.
No more audible leak down under the coach with E6 pedal hold down. I held it down for 120 seconds and lost about 5psi on the gauges.
Oh and I determined the spring brake cans need to be loaded with air to relax the clevis to get the keeper rods out. I can then remove the can and slowly dump the air and let the threaded rod extend, then remove the air hose.
I will block the wheels and do this next week and replace both cans. I figure after 21 years, why not?
David
Sounds like progress.
If that 5 psi drop was after the gauge stabilized, you've got a bit more searching to do. It's probably within spec to pass a DOT roadside, but I'd want to get that reduced even further. Hopefully when you get the rears done it will be better.
5 lb loss in 2 minutes is a dream many busnuts will never achieve.
Only if you have a bad(good?)case of the OCD do you need to go after these peepers, it would take a lot of soapy water and looking for small bubbles with horrible payback on the time and effort.
The trick system is beyond/between the parts you have mentioned, additional parts of the plumbing.
Jim Sheppard may be around, but not checking bus boards for a long time, to see if he can help?
Happy coaching!
Buswarrior
Having a pit or lift greatly effects success on this goal. I went through this on mine two winters ago. Amazing how many small leaks I found. Inline check valves, pressure warning sensors were the biggest slow leaking ones. There is a reason the service manual lists rebuild or replace brake system components on a regular basis. 30 to 50 year old coaches with little touched on the systems other than lining, chambers, or brake valves. Leaks are predictable.
Quote from: buswarrior on February 07, 2021, 06:29:21 AM
5 lb loss in 2 minutes is a dream many busnuts will never achieve....
...Happy coaching!
Buswarrior
It may be a dream, but it's one bus owners should be striving for. Not that we're required to pass DOT roadside inspections, but 2 psi in a minute on a static test and 3 psi in a minute with application of service brakes is the max allowable. If the leak is 5 psi in two minutes on a static test it's really needing some attention. As we all know, these things don't get better on their own, only worse.
I agree that having a pit makes it much easier to hunt down all the leaks. Not having one, I've done it by making it a point to inspect every airline accessible any time anything is opened for any type of work. My current bus was relatively easy, but on our 1964 GM 4106 it did take some effort. Even then, we were able to minimize air leaks to a point where we could easily pass a DOT roadside if we wanted.
Pretty sure Jim Shepard checks this board every day? Just look up his profile? Just never posts I guess... his bus is for sale right now on eagles international
I'm pretty sure Jim is still active on the Eagle's site!
;D BK ;D
Some dash valves do not actually "pop" out. Later Pete and Volvo trucks are like that. The spring brakes do apply but no traditional "pop" of the valve.
One other suspect to check/replace is any QR1 (quick release) valve in the emergency system (if so equipped). Supply blockage with small leaks down stream of the QR1 could trip a sudden application of the spring brakes.
I finally got back to this project. The big freeze we had has messed up everything in my schedule. So, I got the big old spring brake cans off and went to Fleetpride and bought two OTR 3036 spring brakes for $281.67, matching the cans removed.
It took most of a day to fit them back on, replumb, and adjust the slacks to within Eagle book specs.
The book limits travel from 1" to 2". I set them both at 1.25" rod travel. I jacked up the wheels and rolled them and no rubbing ;D
I checked for leakdown on a held brake application and lost 2psi pressure at 10 minutes of hold. I couldn't find any leaks with a soap spray.
I hope my original problem is solved. I will find out soon as I'm heading to Oklahoma next week.
David