We just had a preventative maintenance service in Chattanooga, TN at Choo Choo. While there, it was discovered that our air compressor had lived out its useful life. We had a rebuilt one ordered in and installed, including a new governor.
We're now heading to Memphis, and just before approaching Bolivar, TN - the air system completely dropped pressure all at once. Thank goodness on a 4-lane highway with extra wide shoulders, and on a flat service. The spring brakes engaged enough to slow us down, and we rolled to a stop. We're chocked up.
Doing some troubleshooting with Joel at Choo Choo, the current suspicion is that the 'new' air compressor has failed on us.
Know there are several in this area. Any recommendations on where we should have ourselves hauled towards for assistance? While we do a little more trouble shooting, about time to make that call to CoachNet. Or any further trouble shooting ideas to try? Have already tried percussive maintenance on the new governor, with no improvement.
Thanks!
- Cherie & Chris
(If anyone has useful information that could be of immediate assistance, Chris can be reached at 408-667-9022)
Chris, My first thought is that your drive gear is bad on the compressor
Chris
I would think that if the compressor failed, you would have a slow loss of pressure. Did you lose suspension pressure too? Sounds like an open line for it to go away so fast. I have a quick connect in my system so I can air up independent of the engine compressor. Tapping into your system and pressurizing it may allow you to differentiate between compressor and a bad line.
Good Luck!
I would check that first as well. The added torque of a rebuilt compressor with higher compression on that gear might have finished it off.
BK is close to you . need ## Bob
We were wondering how close BK might be... can't seem to find his number in our address book. If you can send it along, would be marvelous. thanks Bob!
Troubleshooting update: Compressor is spitting out a tiny bit of air, not enough to build pressure. Compressor supplier suspects debris in the reed. Keep in mind, we had the entire engine out-of-frame overhauled last summer.
Talked to Bk . He's calling # you posted
Thanks a ton, Bob! BK on the phone now. And a mechanic from the city here just showed up to offer a hand too.
The shear key probably sheared off one needs to replace that key when installing the gear on the new compressor
good luck
My thoughts exactly Clifford.
Chris find out from the shop that rebuilt the engine if the compressor had/has the fiber coupling. And was it replaced at the time of rebuild or is it the steel one?
;D BK ;D
First thing I'd do is pull the compressor off and verify it is a sheared key. (most likely is)
If it's not a sheared key still could be gears, coupling, or even broke compressor crank.
IMHO that would be A LOT of debris in the reed to cause these symptoms. But hey maybe they know better than I do, but every time I have seen what your describing it's been a sheared key, or broken crank. (yes even with a broken crank the compressor could TRY to spin)
The other common issue is a shattered fiber coupler, but with that you don't usually get ANY AIR at all!
;D BK ;D
Thanks BK.. as Chris already txt'd back (but to update anyone else following along), Joel @ Choo Choo confirmed that our coupler was steel.
The mobile mechanic that Coach-net is sending should be here soon.
Thanks everyone for the advice, feedback and support!
Found the rear brake inversion valve dangling with threads stripped. Compressor seems to be putting out proper air flow (and probably more than the old one was.. thus what caused the valve to pop off?)
(https://scontent-a-iad.xx.fbcdn.net/hphotos-prn2/t1.0-9/1505351_10152080273286158_284973104841790614_n.jpg)
Hmm how about that! Wasn't far off about an open air line after all!
You can block me here too if you'd like!
Good luck in the future!
Sent from my iPhone using Tapatalk
Jackson might be good for parts. good luck.
Straight trucks and some tractors use an Inversion Valve which does not function during normal operation of the vehicle's brake system but operates in the event of a primary (rear service brake) system failure. When the Inversion Valve senses an imbalance of the primary and secondary delivery pressure during an application of the foot valve, it inverts that pressure to release air from the spring brake chambers. This permits the modulated application of the mechanical spring brake chambers on the rear axle(s) to assist the front brakes in stopping the vehicle safely.
If you have any questions or need additional
assistance, contact the ArvinMeritor Customer Service Center
at 800-535-5560...... :-*
Quote from: Ace on April 10, 2014, 07:29:34 PM
Hmm how about that! Wasn't far off about an open air line after all!
You can block me here too if you'd like!
Good luck in the future!
Sent from my iPhone using Tapatalk
First of all... not sure I understand the blocking comment - to the best of my knowledge, we have no reason to block you anywhere?
And yup, those who identified an open air line get the diagnosis score on this one. Glad we kept that balanced with the other alternatives, and didn't start disassembling things quite yet until we got some air in the system and did some further troubleshooting. Many thanks to all!
-Cherie
Quote from: eagle19952 on April 10, 2014, 07:34:29 PM
Straight trucks and some tractors use an Inversion Valve which does not function during normal operation of the vehicle's brake system but operates in the event of a primary (rear service brake) system failure. When the Inversion Valve senses an imbalance of the primary and secondary delivery pressure during an application of the foot valve, it inverts that pressure to release air from the spring brake chambers. This permits the modulated application of the mechanical spring brake chambers on the rear axle(s) to assist the front brakes in stopping the vehicle safely.
Thank you much for the further information.. very appreciated. Also got some tips on the BNO FB page that we can bypass this if needed to get to a safe location.
On the hunt in the morning for a TR-3 locally.. and good to know we have other options if we can't source one tomorrow.
Thanks again all for the help and support
From Bendix
*ReMan pn*..*New pn#*
*101450RX* *101450N*
*Special-Duty Bus Application
Cross References: 280758, 245407, 280758X, 280773, 6D1039, 3902813, 86883026, 36Z1406, 664638C91, 745280758, 6966570, 3902813, 4L293, 664638C91, 90011749, 4111, S-C341, SD281, 3902813, 8084521, G3902813
A cross reference listing means that this valve is a suitable replacement for the part numbers listed. Some changes in air line plumbing may be required.
For instance, if you google 6D1039+valve, you will find that # is Caterpillar's part number for the Bendix TR-3
664638C91...from experience I can tell you at a glance this is Navistar/International Harvester's # for your part.
PS Your welcome.....even tho I am blocked and ignored...:)
Good Luck
Quote from: eagle19952 on April 10, 2014, 08:02:07 PM
From Bendix
*ReMan pn*..*New pn#*
*101450RX* *101450N*
*Special-Duty Bus Application
Cross References: 280758, 245407, 280758X, 280773, 6D1039, 3902813, 86883026, 36Z1406, 664638C91, 745280758, 6966570, 3902813, 4L293, 664638C91, 90011749, 4111, S-C341, SD281, 3902813, 8084521, G3902813
A cross reference listing means that this valve is a suitable replacement for the part numbers listed. Some changes in air line plumbing may be required.
For instance, if you google 6D1039+valve, you will find that # is Caterpillar's part number for the Bendix TR-3
PS Your welcome.....even tho I am blocked and ignored...:)
Good Luck
Thanks... the part number of the valve that came off is 280758, which is not a special bus application one. Seems the difference is the PSI cut on and cut off points?
(and.. have never blocked you here, and definitely not ignoring you here)
Seems the difference is the PSI cut on and cut off points?
Hence the Phone #.
I wonder if the valve leak is not a function problem......related to something upstream....
Not being critical here or judgmental.
But often new problems are related to recent repairs, and I almost always try to eliminate those possibilities first. JMW :)
35 or 70 lbs will both work for their setup
Quote from: eagle19952 on April 11, 2014, 05:44:06 AM
Seems the difference is the PSI cut on and cut off points?
Hence the Phone #.
I wonder if the valve leak is not a function problem......related to something upstream....
Not being critical here or judgmental.
But often new problems are related to recent repairs, and I almost always try to eliminate those possibilities first. JMW :)
Yup... agreed. Especially considering a rebuilt compressor just installed on Monday, and the addition of the air dryer.
We have sourced the part here locally, and it is inbound within the hour. And Coachnet just deployed out the mechanic again to assist (at their suggestion, not our ask.. really impressed with their service). Will hook up the new valve, and see where we are from there. Good to have other eyes and experience and tools onsite.
Best working hypothesis is that the new compressor perhaps uncovered a weak link the system? If there are other theories or possibilities, always happy to hear them.
The new compressor probably had nothing to do with it. Compressors do the same thing whether they are new or old. They compress air. The governor regulates the pressure at which they stop compressing air. The only difference between a new compressor and an old compressor is how long it runs before the governor unloads it. You had the same pressure with the old compressor that you have with the new one.
My guess is it vibrated loose over time and was not caught during maintenance inspections. Fitting might have been cross threaded when installed or the last time it was worked on.
I think the bigger question might be why was it "dangling". Isn't it supposed to be bolted to something? Aren't those two holes for bolts? Where are they?
Bolts just don't unscrew themselves simultaneously.
To me, this seems to point to lack of maintenance and/or inspections. I would imagine it's been dangling for the air lines for a long time, and the vibration strained the threads of the fittings.
You got Craig I never saw one installed like theirs the correct way is mount it vertical with the bolt holes furnished with flex lines going to all 3 ports.
The paper label was still in place and readable I would venture to say that TR-3 is not very old vibration done it in ::)
Best working hypothesis is that the new compressor perhaps uncovered a weak link the system? If there are other theories or possibilities, always happy to hear them.
Well since you asked....the valve is designed (per the statement above sourced from Meritor) to allow limited use of the front brakes to safely stop the vehicle in the event of rear brake loss or failure....So I would want to know if that was what initiated my problem before I was confident in the repair/replacement of the TR-3 as the "solution".
PS. I have seen instances where the valve was not properly anchored because the air lines were shortened because they were re-used as a temporary repair due to a leaky hose.....that never got fixed properly....I usually fired those kind of fixers....And I have seen instances where the lines were to short to begin with and were yanked out by the suspension....causing what appeared to be a stripped thread....these are just thoughts to consider before you go again on your merry way....:)
I doubt their GM has a dual air system Donald from the photo it looks like it blew off at the supply port which is under pressure all the time on their setup
These old buses you can find very creative plumbing and wiring sometimes when I try to help people with problems I wonder sometimes what the hell is this thing doing on the road
They should be on the road he found the TR-3 this AM
good luck
based on their "odd" brake cans (referred to as "mini-mags) I assumed that some one updated the system.....or better said "modified"....
On a different note...the new air dryer is referred to as a an Armada brand...one that I have never of, now I have heard of Armada replacement dryer cartridges...not sure of them, but heard of them.
There should be a plate with 2 holes in it on the back axle it connects to. If that is not it try pouring a bottle of brake line antifreeze in the big line that comes off the compressor and see if the pressure returns after re-installing that line end, start the motor and see if it builds. if it does have it towed to a repair shop and have the brake system checked. also the Pressure protection valve up front would need to be checked.
good luck to you guys!...
Dave5Cs
According to F/B they are on the road again after replacing the TR-3 but Chris does need to clean that mess up the PO left :-\
Sounds like eh!... Clifford thanks for the update. ;D
We are indeed back on the road, thanks so much to everyone who chimed in with advice - and to CoachNet too.
The root problem is indeed traced back to the previous owner not properly mounting the inversion valve when he upgraded to the Mini-Max spring brakes. He screwed the supply line to the TR-3 inversion valve directly into the side of the main brake actuation valve, which over many years of jostling eventually stripped the threading. Our failure was caused by it at last blowing off - instantly dumping all our air.
Plenty of experienced bus mechanics have been down there over the past three years and nobody flagged the problem - I think everyone assumed it was set up that way for a reason.
Now that we've identified the root cause - in the near future as soon as we can find a pit to do the work over we'll get the valve relocated and mounted much more securely directly to the bulkhead. It is also probably a good time to again look over the rest of the air system from front-to-back looking for any other non-stock "optimizations" that might be lingering from the bus's previous life.
Any recommendations in the St. Louis area to get some air system work done?
Cheers everyone,
- Chris
Good thing you were not going off the Rockies when it happened. You should build some ramps so you can get under that thing and perform pm/inspections. They also double as run up blocks, jack blocks, wheel chocks, etc. I never leave home without mine. A simple PT 8X8 cut at an angle suffices just fine. Also good to perform a DOT brake check each morning before departure, even though we are not commercial operators. If you don't know how, pick up a CDL manual from any state. HTH