Need Help with Air Leak

[Depewtee]

Hi All -

I have been searching for an elusive air leak(s) for some time.  I finally opened the access panel in the rear floor and found the source of the hissing.  Now, what is the real problem??  This is what I know...  The engine stop valve is leaking a good amount of air.  It is coming from where the rod enters the valve.  Should be an easy fix, but I do not know the part number.  Anyone know?  Is there a rebuild kit for this valve?



That leak is bad, but nothing compared to the sound of air rushing out from behind the turbo.  Try as I may, I could not see behind the turbo to find the leak.  I spent two days crawling over, under, and around trying to find the source.  During my search, I did find that the curbside tag axle air bag did not have air - the driver's side bag did.  I am not sure if this is related to my air leak problem or not.  Today I pulled the access cover in the rear floor and there is a valve with stainless steel braided air lines coming out of it that is leaking.  One of the air lines feeds air to a solenoid that in turn feeds air to the aforementioned leaking engine stop valve.  This particular valve appears to be some kind of dump valve as there is a rubber boot/flap/protector on one end.  The air is leaking from around this rubber piece (okay, "leaking" is an understatement.  It sounds like an F-16 kicking in the afterburners!).  Are these two leaks related?  Is the air bag not filling somehow related (by the way, I doused the airbag and all related fittings I could find with soapy water and no leaks found.  The bag itself appears to be in good condition).  Here are a few pictures of the leaking valve.  Anyone know a part number?  (Yes, I know I need to buy a parts manual... ).





Thanks,
Brian S.

[luvrbus]

Luke has the parts but most of the time it is the front O-ring .15 cents at Napa real easy fix if the shaft is good
good luck

[wildbob24]

Brian,

That component in your second and third photos is the governor for the air system. Bendix model D2. Should be available at any truck supply (or Napa), but Luke will have them too.

I'm assuming you're working on your 9, since the compressor is mounted sideways. It seems a bit strange to me that there is a line running to the engine stop skinner valve. Usually the governor will have only 2 lines, one from the wet tank and one to the dryer. Is that line tee'd off of the wet tank line?

There should be a couple of valves just inside the curbside engine door that control the air to your tag axles. Perhaps the curbside valve is closed?

Bob

[Depewtee]

Luvrbus,

Thanks for the reply.  I went ahead and pulled the stop cylinder.  It looks pretty bad inside, although I think if I had a new piston cup it would be good to go.  I found a diagram of the stop cylinder in my Service Manual.



Here are pictures of my cylinder taken apart.







Bob,

Thank you as well for the reply.  Yes, I just did a search at www.napaonline.com and it is indeed a Bendix D2.  They are only $13.29 at NAPA.  Should I go ahead and replace it, or do you think something else is causing it to leak?

You were right as well on the two lines coming from the governor.  I went and looked again and the line going to the stop cylinder actually tees off a line that is directly below the governor.

By the way, this is the system on the Prevost.  Any chance there is a valve for the curbside tag axle on it?

I am learning so much about my bus!!!!!!!!

Thanks,
Brian S.

[robertglines1]

Brian, I don't have book on 81   ck to see if it has the manual tag lift valves in the right rear side door for your tag lift or does it have lift control on side panel next to driver. would be two separate air systems involved here. Later models use a norgren valve to control tag lift etc.  let us know what you have.   the Norgren valve will look rectangular or square and have several hoses running in and out of it

[eddiepotts]

Brian, on my 83 there is a solenoid right next to the panel box above the engine. When I hit my kill switch inside it opens and sends air to the plunger. I am sure you have seen yours. My solenoid leaks air. It seems the housing is cracked on the back side. If I ever find out what to call it or a part number I will buy a new one. Run your hand down both the large line and the small one going to the dryer. I had holes in both from the two rubbing together. The larger line was $80 from a truck parts house off the shelf. The smaller one I have not got yet. They were out of them. Those leaks were making allot of noise. Keep up with the pics. Thanks for showing the drawings and what you seen inside your valve.

[eddiepotts]

Brian, I am trying to read what your asking and getting lost. The small line off your governor is going down to your air dryer purge valve. Is that whats leaking or the solenoid valve?

[RickB]

Brian,

Save yourself the trouble and buy a rebuilt stop cylinder and a rebuilt air governor as well. Probably cost you around $50 and you'll be done with it. You may have to adjust the governor so that it inloads at 120psi. It has a set screw right under that rubber cap you said was leaking.

The one you have is so really worn and pitted and the reason there was so much gunk in there is probably your compressor. Around $250-300 with a core. I'm a firm believer in buying rebuilt because they come with a warranty.

Just my two cents

RB

[Depewtee]

Brian, I don't have book on 81   ck to see if it has the manual tag lift valves in the right rear side door for your tag lift or does it have lift control on side panel next to driver. would be two separate air systems involved here. Later models use a norgren valve to control tag lift etc.  let us know what you have.   the Norgren valve will look rectangular or square and have several hoses running in and out of it

Bob,

I have the tag lift control next to the driver.

Run your hand down both the large line and the small one going to the dryer. I had holes in both from the two rubbing together. The larger line was $80 from a truck parts house off the shelf. The smaller one I have not got yet. They were out of them. Those leaks were making allot of noise.

Eddie,

I am thinking that once I replace the governor (just bought a rebuilt one at NAPA for less than $14.00) and the stop cylinder I will have plenty of more leaks to find.  I am thinking there might be one causing the curbside tag bag not to air up (it is really hard, i.e., impossible, to see up into that area).

Brian,

Save yourself the trouble and buy a rebuilt stop cylinder and a rebuilt air governor as well. Probably cost you around $50 and you'll be done with it. You may have to adjust the governor so that it inloads at 120psi. It has a set screw right under that rubber cap you said was leaking.

Rick,

Found the governor at NAPA, but I stumped NAPA and Fleet Maintenance when I showed the engine stop cylinder.  I will do some research and see if I can find one online tonight.  In the meantime, I will clean my old one up and stick it back on and see what happens.

Here is a picture of the Bendix D2 governor.






Brian S.

[Eagle Andy]

Brian , I had the same issues with my Eagle , I talked to Sonnie Gray and he recomended Luke , It's funny I also stumpped the boys at napa when I took them the air kill valve , I took mine apart and cleaned it up and it leaked a litttle so I shot some  WD 40 in and it quit . Not sure for how long but it got me going.

[luvrbus]

That valve is also a Detroit Dealer item if you have one close they may have to order the kit


good luck

[RickB]

They have rebuilt stop cylinders at C&J coach in Minneapolis. Ask for fred at 952-881-0034

Steve, their rebuild guy is really thorough.

RB

[Depewtee]

Success!!!  At least partially.  I installed the remanufactured governor and cleaned up the stop cylinder really good, reassembled it, and reinstalled it.  I then aired the system up and my major leak, the governor, was fixed!  The stop cylinder is still leaking really bad, so I will call C&J and/or Luke tomorrow and see if either has one in stock.  All in all, the hardest part of the job was opening up the access cover - I still have not put it back in place as I want to read up on how to adjust the governor before closing everything back up.  While I was installing the governor I figured out why the tag bag was not airing up...  I surmised that because I was using my portable compressor to air the bus I was not getting enough pressure to fill the bag.  Sure enough, after I double checked everything with just the portable compressor air, I cranked the bus and let it air up with the bus air.  The tag bag filled no problem.  Another good thing I found is that my bus airs up at least twice as fast as before, which leads me to believe I have had this problem the entire time I have had the bus.  I also think the governor is responsible for my air troubles I had on my Talladega trip (see that post here).  Looking back on that post, Niles500 nailed the problem I was having.

Thanks all for the help and I will keep you posted on the stop cylinder.

Brian S.

[robertglines1]

Brian the tag bags are on the secondary air system. and are designed to release air into primary system in a air failure to help you stop safe. That said they will not even inflate till primary system is over about 65lbs.  sounds as if you are good to go.   Bob

[Depewtee]

I can't seem to find the part number for the stop cylinder on the Internet.  Does anyone know of a place that sells the parts manual for an 8-
V71 in a .pdf I can download?