Good Morning,
Did a search and found a similar issue on the other board, but no resolution yet.
Anyhoo. Bus is in storage but need to get it out soon, air system airs up on gauge, dryer does not purge(AD-9) and the pressure can be brought down by cycling the service brakes, park brakes will not release, moved it by applying air to the towing air port to keep brakes released.
I think it is PPV and will order one and replace anyway, can't seem to find where it is, also may be a check valve, trying to figure out from the manuals, but old copies are tough.
Here is the valve Andy Posted.
Part Type: Air Valve
System: Air
Part Name: Pressure Protection Valve
Part Description 1: PR-2 Pressure Protection Valve, 65 psi
Manufacturer: Bendix
Mfr. Part Number: 277147
Vendor: NAPA
Part Number: TWD BENOR277147X
Cost: 41.85
https://www.napaonline.com/napa/en/p/TWRBENOR277147X (https://www.napaonline.com/napa/en/p/TWRBENOR277147X)
Have new cartridge and purge valve for dryer to service while I'm under there.
Any Help with this or experience or pics is appreciated.
More than likely, the fittings will benefit from some penetrating oil, prior to removal attempts.
Proper stuff, NOT WD40...
Commercially available preparations or home brew. 50:50 transmission oil to acetone has been raved about for decades by those who have concocted it.
Get a copy of the coach air schematic for your maintenance log, and mark the repairs. Then you have the history of known and unknown...
Happy coaching!
Buswarrior
On my similar year MCI (if you have an MC-9, that is) the PPV is mounted on the emergency brake tank, which is the passenger side tank between the front wheels. There should be two things mounted there - the E-filter and the PPV. The feed to the governor is after the PPV so that would explain the no-purging, and the feed to the emergency tank is also after the PPV, so no air to release the parking brake. Also no air to the suspension or accessory systems, which include all of the engine air systems.
Penetrating oil doesn't help when removing pipe fittings. Anyway, most fittings on our coach are brass, so they don't rust fast. They are sealed with pipe sealing compound. This stuff can get pretty hard over the years and make it difficult to break loose fittings. If you encounter this, especially on larger ones, heat threads with propane torch some. It will soften sealant and assist in removal.
No, but penetrant can help with the pipe-to-fitting bond.
The whole pipe will twist with the fastener.
That is what one is trying to moderate.
Happy coaching!
Buswarrior
Quote from: chessie4905 on March 17, 2018, 07:58:40 AM
Penetrating oil doesn't help when removing pipe fittings. Anyway, most fittings on our coach are brass, so they don't rust fast. They are sealed with pipe sealing compound. This stuff can get pretty hard over the years and make it difficult to break loose fittings. If you encounter this, especially on larger ones, heat threads with propane torch some. It will soften sealant and assist in removal.
does if there is teflon tape...which goes there. dope is for gas pipe.
Most hard lines that I have on my bus terminate in a 45 degree flare fitting onto a flare to pipe thread adaptor that goes into the casting of the thing you are connecting to - the filter, the PPV, the whatever. As BW says it's real common to have the steel line rust where it it goes into the flare fitting and rotate with the flare fitting when you try to turn it. I've had some flex lines that were pipe on one end and a flare fitting on the other, but those are a PITA.
Quote from: bevans6 on March 17, 2018, 11:31:36 AM
Most hard lines that I have on my bus terminate in a 45 degree flare fitting onto a flare to pipe thread adaptor that goes into the casting of the thing you are connecting to - the filter, the PPV, the whatever. As BW says it's real common to have the steel line rust where it it goes into the flare fitting and rotate with the flare fitting when you try to turn it. I've had some flex lines that were pipe on one end and a flare fitting on the other, but those are a PITA.
careful with the heat too if you have nylon or plastic lines. They melt very fast.
Sent from my SM-N920T using Tapatalk
Quote from: bevans6 on March 17, 2018, 07:25:55 AM
On my similar year MCI (if you have an MC-9, that is) the PPV is mounted on the emergency brake tank, which is the passenger side tank between the front wheels. There should be two things mounted there - the E-filter and the PPV. The feed to the governor is after the PPV so that would explain the no-purging, and the feed to the emergency tank is also after the PPV, so no air to release the parking brake. Also no air to the suspension or accessory systems, which include all of the engine air systems.
I guess I should clean out that e-filter as well, or is it a replace or replace inners sorta thing?
?
Every factory fitting on all my GM coaches use pipe sealant, not teflon. Always hold fitting while loosing attaching line.
The E filter... damned if you try...
If there has been no evidence that it is obstructing air flow...
Maybe let sleeping dogs lie?
Happy coaching?
Buswarrior
Quote from: chessie4905 on March 17, 2018, 04:23:22 PM
Every factory fitting on all my GM coaches use pipe sealant, not teflon. Always hold fitting while loosing attaching line.
must be vintage :)
Quote from: buswarrior on March 17, 2018, 06:23:03 PM
The E filter... damned if you try...
If there has been no evidence that it is obstructing air flow...
Maybe let sleeping dogs lie?
Happy coaching?
Buswarrior
Good morning, I guess it has always been slow to air up, only bus I've ever had, so not sure if that was normal.
What might s sign be? And why leave it alone if I'm changing the ppv out anyway?
If you can get the E filter apart without damage...
The PPV is mission critical, fool with that first, decide about the E-filter based on that experience.
Fast/slow build up... try a test:
Assuming a leak free system...
Build to cut-out, whole system full
Reduce air pressure below 85 lbs
Time the race to build 85 to 100 lbs, engine just idling, no throttle, no high idle.
Under 2 minutes is a pass in this jurisdiction.
A dual system in good shape will rip that off in 45 seconds or so.
Happy coaching!
Buswarrior
Oh trust BW on this one. I opened mine up then took out the old probably original string filter which fell apart. Call Luke and had him send me one. Then when putting the darn thing back together could not get it to seal again. took it back off and tighten it up. The corner of it broke off. Tried JB weld and other things. Nothing worked so It is laying in pieces somewhere between here and the other 4 acreas of field by it. I went to parker and got another very much newer filter housing with small filter in it and ran copper lines up to the tool bay in front and put the filter there so I could drain it easier. ;D
alright, I'll probably lose my guru card for asking this..
i know the ppv is the pressure protection valve.
what is the e-filter ?
On an MCI of a certain vintage (mine is 1980) it's just an in-line air filter to keep contaminants out of the accessory and suspension air system. It's on the output from the dry tank after the pressure protection valve.
Quote from: bevans6 on March 19, 2018, 10:34:29 AM
On an MCI of a certain vintage (mine is 1980) it's just an in-line air filter to keep contaminants out of the accessory and suspension air system. It's on the output from the dry tank after the pressure protection valve.
thanks, but why e- and not a- ?
just curious.
E type filter was a vendor descriptor.
Obsolete now
Happy coaching!
Buswarrior
Must have worked really well at -40°
The E filter is a long way into the system, the contaminants and moisture would normally be left behind by the time the air gets here.
They didn't cause any grief.
That's why they were/are mostly ignored.
happy coaching!
buswarrior
Mine has a small filter under dash with a type of horse hair in it. Filters air going to wiper motors. Occasionally, remove, disassemble, clean mesh in solvent, and reassemble.
So is the PPV the one way/check valve after Dryer that can cause a problem? Or us there another valve?
Quote from: buswarrior on March 20, 2018, 08:53:48 AM
The E filter is a long way into the system, the contaminants and moisture would normally be left behind by the time the air gets here.
They didn't cause any grief.
That's why they were/are mostly ignored.
happy coaching!
buswarrior
Since it is basically a "closed" system, would it not be suitable enough to filter the compressor inlet air properly and then even the compressor would have "clean" air to work with as well, as all the valves downstream, in the first place?
Most air compressors intake is plumbed from the engine air filter in our coaches. Some older or medium duty, or retrofitted, there should be a stand alone filter.
The compressor is a source of contaminants, but that normally drops out mostly in the wet tank, if an air dryer is absent. The air dryer normally captures contaminants. Through neglect, as each loads beyond capacity, the contaminants can get inhaled/pushed deeper into the system.
The PPV - pressure protection valve, via its spring internals, blocks air from filling less important parts of the system, until the brake tanks are up to the setting, then the air pushes past to fill the rest. They usually fail by letting air in before they should, not by obstructing the flo
It is safe to say that every air problem a busnut experiences is due to delayed parts replacement and neglect. Working through the air system in a methodical fashion to catch up the neglectof previous owners is a HUGE contribution to coach reliability.
And keeping the system properly dry, 365 days a year, winter freeze up won't happen.
Happy coaching!
Buswarrior
Ok, got the bus shored up to my liking, got to the PPV, tooke the flarenut fitting loose, the other side is attached to that filter and is too close to the air tank to spin off, so back this afternoon too take the filter off and replace the valve, lol, so close....😉
Also the filter has a blowdown and is one of the cables by the passenger front tire, , not going to open it, thanks BW,
Keep ya posted...😎
Okay, Update time, Got the PPV valve replaced, aired with compressor and fixed the leak that i didn't get tight enough, lol. So aired up and Moved. Also Changed the purge valve, It aired up and got to move the bus. Thanks for all the help.
Now for another issue, not purging, will post a new thread... :)