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Rudolph Diesel, ASE ,Master Heavy Truck Technichian
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Malfunctioning..OPEN position..the bus run..door switches

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I have an International school bus that has a malfunctioning air door. When I put the switch in the OPEN position the door starts to open then it shuts. After letting the bus run much longer and playing with the door switches it gets a little better. However, once you use the door you have to wait two or three minutes before it will work again.
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When your trying to operate the air door and it does not function.


What is the air pressure at your air gage?

When you switch to the open position and the door does not operate do you hear air leaking?

Has the air tans been checked for water?

has the air dryer been serviced with in the last 12 months?

was this problem something that just started ?

or has the problem slowly been getting worse?


Customer: replied 6 years ago.

When your trying to operate the air door and it does not function.

Q: What is the air pressure at your air gage?

A: 40 lbs (the pressure isn't dropping)

Q: has the air dryer been serviced with in the last 12 months?

A: No. The bus hasn't been getting used in summer except bus inspection.

Q: was this problem something that just started ?

A: yes. last used 3 weeks ago for inspection.

Q: or has the problem slowly been getting worse?

A: no it just happened today while driver practiced pre-trip. His test is Tuesday.

Customer: replied 6 years ago.
Actually now that I think about it maybe the pressure did drop. Because I saw the door was a bit flacid. Also, it stops working for a minute after it has just been used.


Thank you for the information!


Im thinking the air seams low, check the governor if this is air brake or air over hydraulic you should be at 120 for a air pressure if no air for brakes bump the governor to 75

here is what else i would check,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,


I would look at the air door cylinder

if there is any moister in the air system,,,,,, air dryer,,,, air tanks,,,,,

This will travel threw the air system and end up in the cylinder

and this will build up and slow it down

if you dis connect the line into the air door cylinder i would put some rust penatrent then some wd 40 in it with eh hose still disconnected slowly work the door/doors if 2/ by hand,,,, Also check the door hinges and or tracks see if any thing is binding,,,, if the door is hinged see if the pins in the door is rusty ,,,They only have so much presser on the door cylinder so if some one is in the door way they don't get hurt,,, so its important to have every thing working freely,,,,,,,,,,,,,,,, Last i would service the air dryer drain the air tanks,,, water is hard on the air system,,,,, tanks should be drained once a week dryer should be serviced once a year,,


If you need parts for the air door cylinder here is a link i have used when repairing our local school buses


There is one seal and gasket in the cylinder But if the cylinder or piston is pitted i would replace the unit,,, it might work for a while after a rebuild but it will fail again,

Let me know if i can help more!

Customer: replied 6 years ago.
Tomorrow morning someone is going to look it over with me. We will try your suggestions. On monday I will take the bus to the shop that sells International trucks and buses. I'm worried about my driver who has to do the MVA road test on Tuesday. I'll keep you updated and get back to you. I appreciate what you have done so far.

Great thank you!

Let me know what come of it

Have a good evening

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