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Old 03-22-2018, 02:37 AM   #1
Mini-Skoolie
 
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Join Date: Jul 2017
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Year: 1984
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Help! air brakes on my bluebird not getting enough psi

title says it all.
my 1984 bluebird bus has been sitting for a bit (maybe 9 months, starting occasionally).
I use it more as a spare bedroom than a vehicle. anyway, it gets up to 50 psi or so and then won't go any higher. And it takes forever to get that high.
Any ideas on what the problem is?

and/or, any recommendations for people in Portland, Oregon who might be able to help me?
-brandon

oh, and I can't seem to get the photos on my post, if anyone is curious about this beauty you can check it out on my Facebook: https://www.facebook.com/brandonlawspdx

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Old 03-22-2018, 06:58 AM   #2
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Year: 1991
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Chassis: T/C 2000 28 foot Handy Bus
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Are all of the drains on the air tanks off?

Have you crawled under the bus to listen for obvious leaks?
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Old 03-22-2018, 04:29 PM   #3
Mini-Skoolie
 
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I ran the engine for 25 minutes today getting the PSI up to around 30. I then crawled under it to listen for leaks but couldn’t hear anything.

Admittedly I know nothing about airbrakes. How do I check to see if the drains are on or off?

I took pictures of a cylinder about 5 feet behind front axle. Is this the compressor for the air brakes?

I know it is kind of tacky but I couldn’t figure out how to post an image in this reply so I just made that picture my avatar.
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Old 03-22-2018, 04:46 PM   #4
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The compressor is mounted to the engine.

The air drains have valves similar to many other ball valves. When they are open, the handle is in line with the body of the valve. When they are closed, the handle is perpendicular to the body of the valve.

Another indicator is: when open, air comes out. When closed, air does not come out.

The drain valves on mine are in a compartment below the drivers side window and are plainly labeled.

If you ran the bus for an extended period and could not track down a leak you may have a problem with the regulator on the compressor.
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Old 03-22-2018, 04:53 PM   #5
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What motor if is a 5.9 cummins the compressor will be on the front left under the fuel injection pump
The drain valves are on the bottom of the air tanks
Pumpup to whatever pressure it will reach and open each valve on yhe bottom of each tank it probably will spray nast water
What i really think is wrong is the unloader valve in the compressor is stuck or maybe the air filter on the pump is clogged severly
The unloader does just what it sounds like it unloads the pump when the desired air pressur is made
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Old 03-22-2018, 05:19 PM   #6
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Quote:
Originally Posted by Rivetboy View Post
What motor if is a 5.9 cummins the compressor will be on the front left under the fuel injection pump
The drain valves are on the bottom of the air tanks
Pumpup to whatever pressure it will reach and open each valve on yhe bottom of each tank it probably will spray nast water
What i really think is wrong is the unloader valve in the compressor is stuck or maybe the air filter on the pump is clogged severly
The unloader does just what it sounds like it unloads the pump when the desired air pressur is made
I called it a regulator. Rivetboy is correct. It is called the unloader.

As to the drain valves, location varies.
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Old 03-22-2018, 09:14 PM   #7
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I had a similar problem with my International Thomas. I replaced the governor and it works great now. Mine was higher up in the engine but with the engine cowling inside the bus off the air leak could be clearly heard.
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Old 03-22-2018, 09:53 PM   #8
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Thanks for the replies everyone.

Ok, so i built a bed frame over the engine compartment (stub nose, you can sit on the bed and drive.) I'll have to take it apart tomorrow and see if I can find the leak. If that doesn't present itself I'll check and see if I can find the air filter on the compressor. I'm not sure how to get to the unloader valve. One thing at a time though.

also, if the compressor is mounted on top of the engine on the drivers' side (maybe under the fuel injector), where are the air tanks for the brakes located?

also, side note, what is that piece that I took a picture of?

Oh and if it helps i can confirm it has a cummins engine.
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Old 03-22-2018, 10:05 PM   #9
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Quote:
Originally Posted by Brando View Post
Thanks for the replies everyone.

Ok, so i built a bed frame over the engine compartment (stub nose, you can sit on the bed and drive.) I'll have to take it apart tomorrow and see if I can find the leak. If that doesn't present itself I'll check and see if I can find the air filter on the compressor. I'm not sure how to get to the unloader valve. One thing at a time though.

also, if the compressor is mounted on top of the engine on the drivers' side (maybe under the fuel injector), where are the air tanks for the brakes located?

also, side note, what is that piece that I took a picture of?

Oh and if it helps i can confirm it has a cummins engine.
Air tanks are usually located along the frame rails. There will be at least three and possibly four of them.

Wet tank
Primary tank
Secondary tank
Auxiliary tank
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Old 03-22-2018, 10:08 PM   #10
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Quote:
Originally Posted by Brando View Post
also, if the compressor is mounted on top of the engine on the drivers' side (maybe under the fuel injector), where are the air tanks for the brakes located?

also, side note, what is that piece that I took a picture of?

Oh and if it helps i can confirm it has a cummins engine.
Mine is a 1999 flat nose BlueBird with a Cummins also. I have an air tank underneath the driver in front of the left wheel that is evidently a dual tank since it has two drain valves on bottom. My other tank is near the rear axle - also on the driver's side. Once you've seen one, they are pretty easy to spot since they are similarly shaped.

My best guess on your picture is your air dryer. Mine's slightly different, but it's newer too. The air dryer is something that needs periodic maintenance too.
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Old 03-23-2018, 12:16 AM   #11
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Yeah, a plugged air dryer equals no air pressure too. You said you heard no air leaks?
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Old 03-23-2018, 07:00 AM   #12
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that piece you took a picture of is the air dryer.. so when you start up the bus and it builds pressure to 30, does that pressure bleed right off to zero when you shut off the bus or does it stay up?

if it bleeds off right away then i suspect a leak somewhere.. if it stays up then the governor is a good place to start..
-Christopher
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Old 03-23-2018, 08:38 AM   #13
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I'd replace the governor first, they are cheap and are a common fail.
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Old 03-24-2018, 03:07 PM   #14
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Quote:
Originally Posted by cadillackid View Post
that piece you took a picture of is the air dryer.. so when you start up the bus and it builds pressure to 30, does that pressure bleed right off to zero when you shut off the bus or does it stay up?

if it bleeds off right away then i suspect a leak somewhere.. if it stays up then the governor is a good place to start..
-Christopher
the pressure stays up for a bit. at least 15 minutes or longer (depending on how high it is). I have included a picture of the engine overhead.

As stated before I'm very much a novice with engines. Can somebody point out to me where the compressor and governor is? And also, where is the best place to buy a governor?



oh, and here are a couple pics of the bottom of the bus, the first pic taken from the driver's side and the second from the passenger's side. What are these cylinders?





thanks everyone!
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Old 03-24-2018, 03:08 PM   #15
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it didn't look like that overhead pic of the engine loaded, here it is:

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Old 03-24-2018, 03:38 PM   #16
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Last picture the top of the engine top right is the air compressor
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Old 03-24-2018, 03:42 PM   #17
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The last picture, of the engine from above, the top right is the air compressor.
In the previous picture the two white cylinders look like the fuel/ water seperator and the fuel filter.
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Old 03-24-2018, 03:47 PM   #18
Bus Nut
 
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Here is a picture of my 1991 bendix compressor off my cummins 5.9
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Old 03-24-2018, 05:08 PM   #19
Mini-Skoolie
 
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Quote:
Originally Posted by bus-bro View Post
Yeah, a plugged air dryer equals no air pressure too. You said you heard no air leaks?
Yeah i have heard no leaks. and thanks to Rivetboy I now know where my compressor is.

So as I understand it, assuming I hear no leaks my protocol is:

1. find the drain valves on the bottom of the tanks (i still am not sure where the tanks are, how big are they? and what do they look like?) and then drain the tanks of their nasty water.

2. check to see if the air dryer is plugged (* picture of this below).

3. find the air filter on the pump for the compressor and see if it is clogged (that is probably the thing on top of the compressor right?)

4. find the unloader valve and see if it is stuck (is this inside the compressor?)

5. buy and install a new governor for the compressor

is the order of these checks about right? and can anybody tell me how i can find out what brand/model of compressor i have?

I'll be heading over to work on the bus tomorrow (sunday)

*this is the air dryer right?
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Old 03-24-2018, 05:36 PM   #20
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goggle image schoolbus air tanks
take the air dryer off the bus find the number and google it
air filter can be any where find xthe tag on the side of it and google it.

You can buy unloader valve rebuild kits but do really want to rebuild it No you do not
You can have it rebuilt or use it as a core 300 bucks up guesstimate
you remove you install.
As others have said service the air dryer and yours does not look like it has been serviced in a while.
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