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Buddy Tennison (Buddyten)
Registered Member
Username: Buddyten
Post Number: 51
Registered: 7-2005
Posted From: 207.68.234.24
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 01, 2008 - 10:44 pm: | |
I must apologize for being so ignorant about things, but I am not a mechanic. Hope you guys can answer some questions.
ALSO SEE PREVIOUS THREAD I POSTED ABOUT AN AIR MANIFOLD.
Have an '83 Eagle. Under normal operating conditions the air system maintains about 130-140 psi according to the gauges. The air compressor does not cycle excessively, or at least I don't think it does. I know that I must have some air leaks somewhere as when we stop for any period of time, the air pressure drops. Also, we still have the air operated door, and we use it while parked, which drains the system.
I have manual drain valves on the air tanks. I try to drain these each time we make a trip and come back in to keep moisture out.
In front of the radiator there is a compartment where I assume the dryer unit is mounted (there is a large "filter" looking thing on top of it, with a tank mounted underneath, and an exhaust hose type thing. That tank also has a manual drain valve.
The other day, I was draining the manual drains, and I happened to push up on this valve, rather than pulling down. When I did, I got a handful of very oily (tan colored) gunk that came out the valve. I'm not smart, but this didn't look normal to me.
Is it normal to have oil in this air system? If so, is it a special oil? Is it required to be changed like engine oil? How often does the filter thing need to be changed? What could be the problem with this?
Also, I have read posts where there is talk about adding alcohol or anti-freeze to the air system. Where is this added, and how is it installed?
I guess I really need an explanation of how to properly service the air system and the operation of the system. Any help, thots or suggestions would be most appreciated.
As soon as the weather permits, I will be taking the spray bottle and trying to find any air leaks I have. |
Debbie and Joe Cannarozzi (Joe_camper)
Registered Member
Username: Joe_camper
Post Number: 82
Registered: 10-2006
Posted From: 71.239.202.82
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 02, 2008 - 7:42 pm: | |
Do not put that antifreeze in a bus with air operated accessories inside unless you like that smell every time you operate them. I think those products are a stop gap measure, or if your going to operate in colder climates and you know you have issues.
I think that folks are mistakenly intimidated by this aspect of our buses. Do not be. A compressor should push no oil. If it does just change it. A properly functioning air dryer will allow NO moisture in the tanks. Bendix says a 2 year service interval an the air dryer. Around 179 bucks for a rebuilt on exchange and an easy job as well as great insurance. I replace the one on my semi every fall weather it needs it or not. In the cold moisture will destroy everything pnewmatic not to mention leave you with no air pressure sitting on the shoulder.
You have the right idea, stop the leaks. Although many potential leak sources on the bus they are not infinite, you can find all of them if you make up your mind. I have found that a large shot of dish soap in a bottle of Windex make a very thick and sticky foam, check it out. They also make a ultrasonic leak detector for the real slight ones. A stethoscope also works. If you have 90lbs after sitting overnight you are probably doing better than most. We have gotten ours to the point that the auxiliary compressor has to kick on only once a day. Ideally, if no air acessories are used our buses should hold 100lb almost indefenitly. |
Buswarrior (Buswarrior)
Registered Member
Username: Buswarrior
Post Number: 1144
Registered: 12-2000
Posted From: 76.68.121.28
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 02, 2008 - 8:47 pm: | |
Hello Buddy
Tan coloured discharge from a wet tank drain is not a crisis. Drain the tanks again/a few times using the same method and see if you can get rid of what has accumulated.
That is a problem with pull cord style drains. Not being to leave them open to let that stuff gloop out over a few hours isn't the best.
A great set-up would have a pull cord for easy draining and a manual turn valve that can be left open for extended periods.
If the discharge was black, or approaching that, the compressor would be your culprit.
Air systems do not have an oil supply, and should only have air in them.
One exception is a radiator shutter system, which requires a special oil to be put into the appropriate device in the engine room. Most busnuts' shutters are removed or inoperative.
As for the air dryer, does your bus "sneeze" when the pressure reaches maximum? Locate the source of the sneeze, and you've got your air dryer.
Joe's annual air dryer swap is an excellent preventive maintenance strategy for a commercial operation, one to which I too subscribe. However, for your bus conversion, you can leave the dryer for a few years at a time, depending on duty cycle, as the desicant is worn out by the amount of air pumped through it, not the age of it.
In general terms, if you get no moisture in the air tanks, the dryer must be performing well, and you can leave it alone. For a coach that has unknown vintage desicant, take a few hours to change it out and check the electrics to it as well. (for the heater to keep it functional in cold climates, if that applies to you)
It would be unusual for you to require air system antifreeze. If the air system has been maintained and kept dry, with regular tank draining and a good air dryer, you shouldn't need alchohol in the system unless you are operating in the near arctic, and then, only as good insurance.
Air system freeze ups are directly related to poor air system maintenance.
As for air compressor cycling, the air gauge gets to maximum, and when the world is perfect, it should stay there, until you use some air.
In reality, while driving, the gauge will start going down. Hopefully, this takes many, many minutes, (hours?) before it stops dropping, and starts back up again, as the compressor cuts in.
To give you an idea, DOT regs suggest the coach shouldn't lose more than 3 pounds of air in a minute, shut off, parking brake released and holding a full brake application.
Thank you for asking, there are only dumb answers.
happy coaching!
buswarrior |
Brian Elfert (Belfert)
Registered Member
Username: Belfert
Post Number: 68
Registered: 7-2006
Posted From: 209.98.146.235
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 03, 2008 - 10:06 pm: | |
I don't know why you would replace the entire air dryer every two years. The cartridge, yes.
My bus will hold over 100 lbs indefinitely during the summer, but loses all air overnight during the winter months. Right now my air governer seems to have ice in it and I can't build any air at all. The previous owner did little, if anything to the bus but drive it so I've had to bring things up to par like replacing the air dryer cartridge. |
Debbie and Joe Cannarozzi (Joe_camper)
Registered Member
Username: Joe_camper
Post Number: 83
Registered: 10-2006
Posted From: 71.239.202.82
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 04, 2008 - 12:32 am: | |
Not all dryers have a removable cartridge. There are 2 different styles they produced before the ones with a spin on element. Both need to either be rebuilt or swapped out. You guys with the spin on cartridge better make sure to check the heating element when you service too.
Buswarrior brings up a good point about the heating element. In the cold if you don't heat the exhaust port the moisture it is discharging will eventually freeze the port closed. When the compressor kicks on it turns on that element and by the time it sneezes there is enough heat at that exhaust port to keep the moisture liquid. However most folks operate in warmer climates and the heating element is worn out in temps that do not even require it. Failure of the dryer is often due to that heating element failing. I have run the power to it through a switch on the dash so I can turn it off when warmer and operate it only when needed. Haven't had a heating element failure since. Probably not necessary considering my service interval but you folks with the spin on elements this would be a good idea, the heating element would last a lot longer. |
Buswarrior (Buswarrior)
Registered Member
Username: Buswarrior
Post Number: 1148
Registered: 12-2000
Posted From: 76.68.120.223
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 05, 2008 - 2:50 pm: | |
Hello.
When you are paying a wrench, the time to change desicant, check the power, wonder how long the heating element will last, fool around, it is just as cost effective to swap the entire unit for a rebuild and trade in the core.
Reliability is the watch word in commercial service, and this swapping is becoming quite popular in northern climates.
Can't beat the price!
Of course a busnut has a different cost/benefit model to work with, so....
happy coaching!
buswarrior |
Brian Elfert (Belfert)
Registered Member
Username: Belfert
Post Number: 71
Registered: 7-2006
Posted From: 209.98.146.235
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 05, 2008 - 11:25 pm: | |
I missed the part in Busswarrior's first post about commercial operations swapping the entire dryer. That would make sense with today's obscene labor rates.
I paid I think $22 for my last reman AD-9 dryer cartridge, but that was on sale right before winter. A reman purge valve cost another $80 or so. Brand new AD-9 air dryers were on sale for $230 which seems to be less than a reman most of the time. |
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