Hi Guys -
(This is a copy of my BNO board. If don't spend time there, you might not get the 'inside jokes' - but I'll be happy to explain :))
Back again, and same old problem. I was sailing smooth, not a hitch and happy as a clam. Did Jack's Bussin' 10 (what a great rally!) and - on the way back to his place (for the BYOB thingy) - I stopped for some much needed fuel.
Fired her up and... no air pressure. Had enough to safely move away from the pumps, but nothing (revving,tapping, banging, screaming, begging. cursing) would load the compressor.
Oh, now and then the needle would rise a few pounds but it would always stop short of 'driveable' pressure.
Jack, BK and Tom (White Eagle) came over to assist, but nothing worked. So we filled it with shop air in hopes of nursing it back to Jack's.
Well, halfway there (here) it started making air again. Right up to 160 psi when we shut her down (bleeding it to 90 psi first).
Since being here, she makes air every time we crank her up. And - like Jack says - how do you diagnose a problem when everything is working?
So, consensus of opinion is: Got to be 1) the unloader valve or 2) the governor (and we all know how well I get along with governors :'().
Current thinking is: Just replace both to be safe (and keep the "old" ones as spares). Any other thoughts?
The governor is an easy switch (except in White River Junction) but changing the unloader requires some major surgery.
So if there's something we're missing, I'd sure like to know before lighting the ol' blowtorch.
Thanks much,
Nellie Wilson
I think you have been given some good advice. Had that happen on my first coach, and took it to the mechanic who replaced both ($240). Now that was a few years ago!!!
Mine was a little different in that I was not sitting at the fuel pumps, I was driving, and watched as my air went down. Buzzers came on, I pulled over and smacked the compressor with a hammer. It began to work again, but air is no play thing on a bus.
Repairs were done very quickly, but I learned how something NOT major can shut you down, if you are not careful. I was more concerned about hammering the spring brakes, and being stuck in the middle lane of I-10 in rush hour! :o
Nillie, if you have a air dryer that is their way of saying I need attention also.
good luck
While the dryer may need a rebuild, the problem is probably the governor. It most likely stuck. It's about $15 to replace. You could probably tear the old one down and rebuild and lube it, but the idea of having a spare is not a bad one.
However there is one other concern. You said your bus built air to 160 lbs. I hope that's a typo, or some metric number, because that's dangerously high and indicates even more problems if correct. Please clarify.
craig
Are MCI's different than most I thought the relief valve would pop at 130 # on the tank ? they do on a Eagle
good luck
Quote from: gumpy on January 14, 2010, 04:42:12 AM
However there is one other concern. You said your bus built air to 160 lbs. I hope that's a typo, or some metric number, because that's dangerously high and indicates even more problems if correct. Please clarify.
craig
BK had tried to re-adjust the governor to get it to start pumping air, which it would not do. On the drive to our place it suddenly started pumping and with the governor at the new setting it hit 160. Governor is now re-set to 120. We know compressor will pump up and we hear no obvious air leaks. Problem seems to be in compressor control (governor and unloader). On her MC-5, unloader is located directly under a floor framing mamber with about less than 1" clearance. Jack
For those that don't have it here is a good place to go for trouble shooting a air system
http://www.bendixvrv.com/itemDisplay.asp?documen... (http://www.bendixvrv.com/itemDisplay.asp?documen...)
hope I got it right if not just go to the bendix site
good luck
Quote from: JackConrad on January 14, 2010, 04:55:00 AM
BK had tried to re-adjust the governor ...
Oh, well, that explains it!! ::)
Curious why the pressure reliefs didn't blow at 130, though. Something's not right there. I'm pretty sure there are supposed to be some reliefs somewhere in the system.
Rebuild the governor and check on the relief valves. It's quite possible the governor is gummed up and not shuttling properly. If it's stuck in the unload position, the unloader valve will be open continuously. Yeah, it's possible it's the unloader valve, but it's more likely the governor.
Mine did that several years ago. Only a problem when it was cold and I first started up. I could smack it with a screwdriver handle and get it to work. Once it started working it was fine till I shut down and it got cold again. I bought a new one, but then cleaned and lubed the old one and put it back on. No problems since. The new one is my spare, now.
At a 160 # it should have sheared the compressor drive key also she got away with one the lucky dog
good luck
from the MC-5C manual: safety valve is set to 150 psi. it's adjustable, by adjusting the preload on the internal spring that loads the valve ball. there is a pin that sticks out of the body, you can pull on the end of the pin to unload the ball and force it to exhaust. If you pull on the pin and it doesn't exhaust, take it apart and clean it, and set it to whatever pressure you desire (standard is 150 psi) by adjusting the preload nut. There are no rubber seals to go bad, just steel balls and seats and such. It's on the wet tank, I do believe. the dash gauge is probably not all that accurate, but it wouldn't be impossible to just whip the thing out and test it if you think it's bad, if you had a source of 150psi air. here's a good one "leakage at the exhaust port should not exceed a 3" soap bubble in three seconds"... ;D
On the basic problem, I would change the governor, since it's job is to tell the unloader when to unload, and to tell the air dryer when to purge and all of that. It's the guy in the middle. You could have had a frozen/blocked signal line from the wet tank to the governor that would have caused exactly your symptoms.
I hope this helps a bit. As additional MC-5C air system trivia, the dash gauge reads from the dry tank while the low air warning buzzer, light, and the generator cutoff switch read from the accessory tank.
cheers, Brian. You ever want anything from the official MC-5C manual, ping me and I'll look it up for you. I've read it cover to cover now anyway, but I seem to be trying to slowly memorize it...
I don't understand about the 150 psi setting there are a lot of Bendix valves in the system that the 150 psi exceeds their working pressure.
And I am almost positive MCI and Eagles use the same Bendix valves
good luck
Clifford, they may use the same valves, but everybody knows that everything is better in an MCI! lol. ;D
Give me a break Ed or I'll send this rain south to Yuma
good luck
I have no idea about the 150 psi and other valves, all I have is page 4-20 in the MCI manual to go on. My air brake safety course also said the DOT specification for safety blow-off is 150 psi, so the number came up twice. Maybe they picked 150 psi exactly because that is where the other components reach their maximum operating pressure, so as not to exceed that?
this is the valve in the MCI manual, the ST-1: http://www.bendixvrc.com/itemDisplay.asp?documentID=4047
the bendix datasheet suggests 150 psi for the pressure setting, with a cut-out pressure of 125 psi on the governor. I suspect the reasoning is that the safety valve won't reseat until pressure drops to 135 psi, and they want to maintain a 10 psi headroom between those two points.
Brian
Rain? ...you got rain up there? Really? clear skies and 85 degrees here in the Foothills yesterday, and clear skies again this morning. Only had rain one day since we got here on the 27th of Oct.
We're having a heat wave up here, forecast is up to 35 degrees today. Fahrenheit. All of a sudden the difference between Celsius and Fahrenheit really means something...
Brian
Well i just checked the forecast for here and we are supposed to be a little cooler today, and we do have a wind advisory which means we are likely to have a dust storm later today.
Brain, I'll stick with 130 #per Eagle if you check most air brake chambers are good up to 120 or 125 # max depending on the manufacture.As per my instructor in the Bendix school follow your manufactures recommendations so if MCI says 150 # so be it.
FWIW some Eagles are a 150 # for the dual air system and are regulated to the brake chambers but mine is 130 #
good luck
I'm curious now, what is the governor cut-out pressure normally set to on the Eagles? MCI calls for 115 - 118 psi, the bendix data sheet referenced 125. Mine is actually set to 118. I wonder what pressures the non-adjustable ones (the ST-3) are available in? the sheet doesn't mention, it just says the pressure setting is stamped on them.
I guess I should take mine off and test it. You are supposed to maintain it every 50 K miles. I wonder what the true average maintenance interval in practice is? :o
Brian
Quote from: Ed Hackenbruch on January 14, 2010, 07:06:53 AM
Rain? ...you got rain up there? Really? clear skies and 85 degrees here in the Foothills yesterday, and clear skies again this morning. Only had rain one day since we got here on the 27th of Oct.
Just quit raining in Tucson. Now the sun is coming back out. Outside it smells so good and clean...very nice.
God bless,
John
I haven't read the manual on either MCI or Eagle in so long I could not quote it word for word.
But I learned a lot from a guy who had & maintained 13-14 MCI's at a time (yeah he had poor taste, but knew his stuff!) and you could jump in any one of his MCI's and fire it up and in just a couple minutes it would be up to around 140 and spitting and would run right at 140 all day long! He has been around buses much longer than I have and has "been doing it this way for ever!" in his own words.
Personally I usually set mine up for 125-140. FWIW
Also we could not find anything wrong with Nellie's bus except it would not build air and or first thought after adjusting the governor. And pulling the hose off the intake and finding it wasn't drawing any air either was that #1 it either had hung unloader valves or had broken or stripped the fiber drive gear, or sheared the key!
But when driving it back to Jack's and it went to 150-160 I knew the drive gear and key way were fine! So I'm still guessing unloaders, but once I thought I was wrong, and it turned out I was mistaken! ;)
Jack shouldn't need much more than an inch to remove the intake manifold if you can get the bolts out. The hardest part would be getting in there with your needle nose pliers to swap parts (if you can get a kit that is!). But then again, I'd think that a guy who retired from being an EMT might have some hemostats with curved ends laying around somewhere! ;)
;D BK ;D
I have put air to my air system and when trying to go over 130 lbl it starts dumping air continuosly. The weather is sunny every day in Yuma. Jerry
The governor is certainly cheap enough to just change out on suspicion. Although I have heard of cleaning the old one up and keeping it as a spare, I am not sure it is worth doing. I did do that with my last bus, but it had a governor that is no longer manufactured and cost over $100. if you could find someone with old stock. I would think that most of the time, if you are going to the trouble of changing out a part, you might as well use a new one instead of one that will just probably be okay. That is, of course, unless you really want to set yourself up for another repair since that is part of the hobby. I bet there are some busnuts that would find a lack of failures and problems terribly frustrating.
"I have put air to my air system and when trying to go over 130 lbl it starts dumping air continuosly."
If you air up your system with external air, and go past the cut-out pressure of the governor, the governor will sense that and signal the air dryer to purge. The air dryer purge valve opens and dumps air. Since the governor can't signal the external compressor to stop supplying air the way it does to the bus compressor, the air feed continues and the air dryer continues to purge all of the supplied air. It will continue to do so until the supply pressure falls below cut-in pressure, when the governor tells the air dryer to stop purging. I set my compressor that I use to externally fill the bus to below cut-out pressure so that this doesn't happen. In other words, it's normal.
Brian
Quote from: Lin on January 14, 2010, 10:24:06 AM
The governor is certainly cheap enough to just change out on suspicion. Although I have heard of cleaning the old one up and keeping it as a spare, I am not sure it is worth doing. I did do that with my last bus, but it had a governor that is no longer manufactured and cost over $100. if you could find someone with old stock. I would think that most of the time, if you are going to the trouble of changing out a part, you might as well use a new one instead of one that will just probably be okay. That is, of course, unless you really want to set yourself up for another repair since that is part of the hobby. I bet there are some busnuts that would find a lack of failures and problems terribly frustrating.
Lin while it is true that it is cheap enough to replace them with a new one.
#1) it's not always practical. Say at midnight on a lonely stretch of hwy, or out in the backwoods miles & miles from nowhere. Or in bad weather where it's easier to pull one out of a bay and change it than to unhook a toad and go find a new one (or worse yet find a ride if you don't have a toad)
#2) even new ones can be bad. (we had one go back on the way to FL and had it replaced by WW Williams $260.00 w/service call to McDonald's where we were and group could get off the bus! And then once in Florida it had to be replaced again by Orlando Detroit Diesel Allison for another $58.00 parts & labor total)
Also they can be remote mounted to make them easier to get to and replace or adjust! (our Setra's come that way from the factory!)
FWIW
;D BK ;D
When my governor failed it would build up air just fine but to 150psi when it should have been 82!
BK,
Agreed, having a spare part can be useful. However, since even a new governor can be bad, it would seem that one is being particularly optimistic in a believing the bad one you removed, cleaned, and never tested is a dependable backup. It may be better than having nothing, but it would be better to keep another new one as spare. I realize it is highly unlikely that anyone would do it. I know that if mine failed I would do exactly as you say, but when the time came to use it, I would only do so if it was unavoidable.
Bryce, when you replace D-2s do you use reman or new, OEM or aftermarket?
Quote from: DaveG on January 15, 2010, 04:22:38 PM
Bryce, when you replace D-2s do you use reman or new, OEM or aftermarket?
Yes.
OK yes all of the above mostly depending on what is readily available at the time. If I can get new I try to get NEW regardless of OEM or after market. If all I can get is re-manned then re-manned is what I get! HTH FWIW
;D BK ;D
I agree with Lin, new ones are only $20.
this is drifting a little but re Nellie's problem, does she get a lot of gunk in her wet tank? JUst seems odd that she did this awhile back and problems again. Obviously if the gov is cheap and easy to change start there.
Quote from: gus on January 15, 2010, 08:51:23 PM
I agree with Lin, new ones are only $20.
$26.00 for a new aftermarket over the counter at an off brand parts place in PODUNK, MS just today! (Sat. 01/16/10) Don't ask me how I know this! ;)
;D BK ;D
And no it wasn't one of my buses, but he was hauling my customers and I was there too and had the tool box! ;D
Lin,
When my old type governor failed I just replaced it with the new truck type. The old one was not only strange looking but nothing like the one shown in the manual?? It is mounted high on the firewall, not on the compressor.
As I remember the only difficult part was in figuring out which line went to where because the two governors were so different looking. In the end it did not take long to do the actual connecting and from now on it will be much easier to replace.
Hey Zub-Zub, you make a good point.
Jack already picked up the gov. and the unloader kit so, obviously, I'll replace the old. But that still doesn't tell me which failed or why it failed. Next time I air up, I'll give the tanks a good purge. Maybe lay some cardboard down first, make it easier to see what comes out?
To be honest, always been hesitant to bleed those tanks... afraid the valves will never close again :-[
I know, I know... I'm such a wuss.
But I purge my ping tank every time, and never get anything suspicious coming out.
I've heard of guys putting a pull cable on those bleeder valves (to make then accessible). Any thoughts on that?
Nellie Wilson
Nellie, i put those on all of my tanks on my 5A this summer. They work great, cost about 15 bucks at napa. They screw right in, hardest part, (which wasn't that bad ) was routing the cables so they are out of the way. Good cheap project.
Gus,
That was on my last bus that I sold about 1.5 years ago governor and all. The way you went was probably the best was to do it, but the part was available nearby so I took the path of least resistance.
I installed pull cord drain valves on the wet and emergency brake tanks on my 5C this summer (the two tanks between the front wheels). Valves were $7.95 at Traction. I routed the cables up and into the fuel tank filler area, I can drain the tanks easily. I drilled a couple of holes in the front wall of the fuel tank bay behind the front wheel, up high.
In Canada, DOT daily inspections on air brake equipped vehicles include draining all the tanks (as private vehicles we aren't subject to DOT regulations, but knowing what they are is a good idea). It probably doesn't get done that often, if you mean draining to zero, but at a minimum the wet tank should be opened up and allowed to spit for 10 or 15 seconds after every day of driving that gets you say 500 miles, and particularly when driving in humid weather or cold weather. It lets you see what is getting past your air dryer, and in particular lets you see if any oil is coming out. If you pull the valve and it doesn't seal up again, that's a good sign some junk was in there to block the valve. it's quite common, even with new valves, that if you drain all the way down they will hiss and leak a bit as the bus starts to air up, until there is a little pressure for them to work against.
Brian
Thanks for that Bevans6 -
You made me recall that, yeah, I actually did drain those tanks at one point. And they did hiss and spit for awhile... and I thought "Oh sh**! Trying to do the right thing and screwed everything up." They soon stopped spitting but I never dared touch them again. :-[
Like I said, a wuss!
So - displaying my encyclopedic ignorance - when do I drain them? When they're chock full of air (right after shutdown) or do I let the bus sit awhile first?
And how about that back tank - the one on driver's side just forward of the drive wheels. Mine (MCI) is in a compartment in the rearmost luggage bay. For that matter, how about the accessory tank? Do I drain those too?
Man, all this tank draining is gonna cut into my cocktail hour... thank God for KFC and Dominoes :)...
Nellie
I would drain them, or at least the wet tank, in the morning before you drive the bus. The routine is (coffee in cup) approach bus, open the all the engine bay doors, check oil levels, look for stuff that fell off, look specifically for air hoses that may be chafing, drain the ping tank (remember if you stopped the bus while the compressor was compressing, there may be pressure in the ping tank. If you stopped the bus just after the air dryer purged, there is no pressure at the ping tank. Big difference in how much stuff comes out and sprays all over your glasses. I know this from experience...). Next go up and pull the cord on the wet tank and look at what comes out (at least air should come out. If there is no pressure at all, start the bus and build up some pressure). If nothing ugly comes out, then I would start the bus, build up pressure and go through the rest of the daily inspection (air brake system checks, lights, lug nuts, tire pressures).
I would drain the dry tank (rear of drivers side luggage bay), parking/emergency tank (curb side between the front wheels) and auxilliary tank (under the drivers seat) routinely. For me that varies with usage (and on a daily basis "drain" really means open the valve and look at what is coming out, not really drain to the end). Before and after any long trip. Weekly if I am using the bus regularly. Any time that I am doing maintenance. If I ever get water out of the wet tank I pop the drain all the tanks. I make a point of draining all the way down, in a specific sequence, whenever I am doing a proper inspection of the bus, the equivalent of a DOT monthly or 10K mile inspection. If you fill and then drain the tanks in a specific sequence you can check and verify the operation of many of the check valves and pressure protection valves, and the emergency brake system.
cheers, Brian
Nellie,
I always drain my tanks when I shut down in the evening while they are still hot just in case it is freezing the next morning. I don't try to drain them when it is freezing.
Carry a spare drain or two since they are so cheap. Some of them can be changed without even getting underneath the bus.
They won't drain very well unless you have air pressure.
More often draining is better than not so often.
The idea put forward for draining them in the morning is that hot air can hold more moisture than cooler air, so letting the air cool lets the moisture form (like dew overnight) and you get more actual water out. For me, it's almost moot - you will probably get just as much actual moisture out, in whatever form, no matter what you do. I like the idea of doing it as some sort of routine, morning or night, and either can be worked into testing the compressor function, which is about the most important part of the routine. Doing it at night after running all day has the great advantage of giving you a little time to fix anything you find, rather than putting it off because you were supposed to be on the road a half hour ago, and the pressure will still be high even if your bus bleeds down overnight.
Brian
Some philosphic considerations:
If it is below freezing, and there is water in the tank....
Will anything come out when you open the drain?
And:
He who shuts down with compressor unloaded plans to stay until spring?
happy coaching!
buswarrior
BW -
I got this one:
"If it is below freezing, and there is water in the tank....
Will anything come out when you open the drain?"
But what does this one mean?
"He who shuts down with compressor unloaded plans to stay until spring?" So, I shouldn't (let it unload) or I should?
If a man says something and there's no woman around...
is he still wrong? ;)
Nellie
If there is moisture in the controls for the compressor (governor/unloader/signal lines), or there is moisture in the movement of the purge valve in the air drier...
Which position do you want it all in when they freeze into place?
Hint: You can control too much air with your brake pedal, you can't do anything with no air.
Most of the time, the heat from the passing warm compressed air will melt the lick of moisture in these bits before cut-out, so you are blissfully unaware. A leaky air system that goes to cut-in shortly after shut down has the unintended by-product of saving one's unwitting self from one's self, by moving to cut-in before the pieces get cold.
But if these bits freeze in the cut-out position, there is no flow of warm air, and there will be no melting by the way described above.
The old time drivers who would immediately open and leave the drains overnight also unwittingly set themselves up for success in the morning...if they could get the drains closed again...
I'll leave that last question to those better qualified in the insertion of feet to mouth.
happy coaching!
buswarrior
Quote from: Nellie Wilson
If a man says something and there's no woman around...
is he still wrong? ;)
Nellie
OF course not! But once I thought I was wrong, but it turned out I was only mistaken! ;)
;D BK ;D
If you try to open the drain valve when it is frozen you may break the valve or the cord.
If you do get it open and it is broken it won't close again.
If you're lucky and the valve is easy to reach like on my wet tank you can replace the valve.
If it is underneath at the front axle like my dry tank then you have a real problem.
All the above is the reason I drain right after I stop for the day or even during the day before I stop. I don't ever try to drain when the air is cold and the temp below freezing.
Just the air escaping suddenly and expanding can make the valve freeze open so it pays to drain it slowly or in spurts.