MCI 102c3 6v92ta Mechanical Won't Air Up

[luvrbus]

Found an air leak in the fold out step actuator so I removed that line and capped it.  Tomorrow after church I will go around with my spray bottle and try to find more.  The only air I hear is the air dryer filling up, but when I go under and feel around all the fittings I don't feel any air escaping so I am assuming the sound is normal.  I must have more leaks somewhere because I can't get it to build up to 120 psi or where the air dryer purges.

If you have air wipers check the dash area the wiper controls can leak enough to prevent air up

[Jcparmley]

Ok, I didn't think of that.  I will check tomorrow.

If you have air wipers check the dash area the wiper controls can leak enough to prevent air up

[Jcparmley]

Ok, I spent my whole day off today looking for air leaks.  I believe I got them all.  I am now able to build pressure to over 120 psi.  However, my air dryer did not purge.  I kept waiting but nothing happened.  I tried to release the breaks but didn't have any success.  They must be rusted to the drum.  I tried shifting back and forth to try to release them but didn't have any luck. 

[tr206]

Ok, I spent my whole day off today looking for air leaks.  I believe I got them all.  I am now able to build pressure to over 120 psi.  However, my air dryer did not purge.  I kept waiting but nothing happened.  I tried to release the breaks but didn't have any success.  They must be rusted to the drum.  I tried shifting back and forth to try to release them but didn't have any luck.

First chock your tires make sure the slack adjuster can be pulled back (may need a flat screw driver or prybar) this means your brakes are released take a big hammer pound on the edge or outer part of the drum if that don't do it tap on the metal part of the brake shoe . The drum will ring if they are released and solid sound if they are not. Remember you have upper and lower shoes both maybe stuck. If you can't reach the drum with a hammer find a solid steel shaft the right lenth also a good air hammer may work.

If your parking brakes won't release and you want move the bus into the shop like you said you can back the slack adjusters off can be a little tuff to do but can be done if they are manual slack push the keeper in may have to tap it in use a 9/16" 6 point socket and longer ratchet normally counterclockwise to back it off you have to pull hard at first. auto slacks same thing only many different designs you'll have to look it up. Remember you won't have parking or service brakes on that axle make sure your other brakes are setup before you move it and may have to break the shoes free after you back off the slacks. Good Luck!

[luvrbus]

Ok, I spent my whole day off today looking for air leaks.  I believe I got them all.  I am now able to build pressure to over 120 psi.  However, my air dryer did not purge.  I kept waiting but nothing happened.  I tried to release the breaks but didn't have any success.  They must be rusted to the drum.  I tried shifting back and forth to try to release them but didn't have any luck.

The governor controls the purge cycle on the drier it could need adjusting you may not be reaching the psi the governor is set for or the drier is not getting the signal from the governor

[buswarrior]

Confirm pressure in the parking tank, or you are wasting your time bashing on things.It is blind to the dash air gauge.

With all the trouble you have had, absolutely no assumption of proper function can be made.

A tire gauge fits neatly onto a male air hose fitting...

Happy coaching!
Buswarrior

[Jcparmley]

Is the parking tank is under the bus by the front axle on the passenger side, correct?  I can crawl under there and put a gauge on the tank where the moisture release valve is.  Otherwise, I have a male hose fitting in the rear passenger engine hatch where I hook up my external air compressor.  I could check it there as well. 

Confirm pressure in the parking tank, or you are wasting your time bashing on things.It is blind to the dash air gauge.

With all the trouble you have had, absolutely no assumption of proper function can be made.

A tire gauge fits neatly onto a male air hose fitting...

Happy coaching!
Buswarrior

[buswarrior]

Take the pressure at the tank, taking it back there doesn't cornfirm what you need to know, the real pressure in that tank.
First clue is presence of healthy air when you open the drain on the parking tank. A male airline fitting may screw into what you have there, if you"re lucky.

Using what strategies, how many times, did you attempt to release the parking brake? Did you wait for the air to recover between attempts? With the bus in your condition, there's a half hour of stomp, release, forward, backward, leaning on it with the drive train, air build up, stomp, etc, before ever thinking about leaving the driver's seat.

The lack of air drier blow off is also still a highly susicious issue, pointing to continued air system integrity problems. Changing parts willy nilly just introduces more self inflicted malfunctions.

Does the air pressure distinctly stop climbing at EXACTLY the same place on the gauge, every time it builds back up?

Put down the tools, stow the keyboard, and get back in the driver's seat...

Happy coaching!
Buswarrior

[Jcparmley]

I spent well over an hour doing the exact procedure you recommend.  I always let the air build up before releasing the brake, doing a hard stomp and putting in forward and reverse.  My gauge always stops at the same spot every time.  I have drained all the tanks multiple times.  I spent the entire day using soapy water to find all the leaks.  I sprayed down every tank and air fitting I can find, including taking the windshield wiper control unit out and inspecting for leaks.  I have followed all the instructions that I have been given.  Everyday I work at it some more and am very thankful for all the advice. I
I will hook up a pressure gauge to the Brake Tank and see what the pressure is and let you all know.  Thanks for all the help everyone, I really appreciate it.

Take the pressure at the tank, taking it back there doesn't cornfirm what you need to know, the real pressure in that tank.
First clue is presence of healthy air when you open the drain on the parking tank. A male airline fitting may screw into what you have there, if you"re lucky.

Using what strategies, how many times, did you attempt to release the parking brake? Did you wait for the air to recover between attempts? With the bus in your condition, there's a half hour of stomp, release, forward, backward, leaning on it with the drive train, air build up, stomp, etc, before ever thinking about leaving the driver's seat.

The lack of air drier blow off is also still a highly susicious issue, pointing to continued air system integrity problems. Changing parts willy nilly just introduces more self inflicted malfunctions.

Does the air pressure distinctly stop climbing at EXACTLY the same place on the gauge, every time it builds back up?

Put down the tools, stow the keyboard, and get back in the driver's seat...

Happy coaching!
Buswarrior

[luvrbus]

If you have help with someone pushing the brake pedal down and if you can get under the bus to see the DD3 brake chambers if you notice any movement pushing the pedal, then you have air pressure or remove the supply line and you can hear it, the locking port supply is on the front where it mounts to bracket ,A DD3 brake will release without pushing the pedal if the air pressure is good and locks are not frozen from rust, it just takes longer,you are told to use the same process with spring brakes which I never do BTW

[Jcparmley]

I asked my diesel mechanic to come to and do what you suggested.  He said he can hear the air in the chamber but the tensioner and the shaft was not moving.  He thought either there is a problem in the chamber or the brake shoes are rusted to the drum.  We had a lot of rain and the ground is to soft to jack up the bus right now.  In a few days it will freeze again and we will jack the bus up, get under and hammer the drum to see if it will release.  If that doesn't work then I will probably need to look at the chambers themselves.

If you have help with someone pushing the brake pedal down and if you can get under the bus to see the DD3 brake chambers if you notice any movement pushing the pedal, then you have air pressure or remove the supply line and you can hear it, the locking port supply is on the front where it mounts to bracket ,A DD3 brake will release without pushing the pedal if the air pressure is good and locks are not frozen from rust, it just takes longer,you are told to use the same process with spring brakes which I never do BTW

[luvrbus]

When it dries up  slide under and pump new grease into the lock there is a grease zert on the bottom of each chamber pump the old grease out, the fitting is hard see but it is there 

[Jcparmley]

I will grease the chamber and let you know how it goes.

[chessie4905]

Don't  go crazy with grease.

[Jcparmley]

I'm still struggling to get this bus to release its breaks.  It has been very cold and I haven't been able to get out there.  I did get the rear of the bus jacked up so the mechanic could get under and see if the canisters are releasing the brakes, however, to my bad luck, when the mechanic came out the bus wouldn't air up past 50 psi again.  Three weeks ago I had it airing up just fine over 100 psi, but the brakes wouldn't release.  Now it won't air up past 50 psi.  I don't hear any leaks and three weeks ago I chased down a the leaks with the soapy water bottle.  Interesting thing about today is the accessory tank didn't have any air in it.  So I am thinking their is a valve sticking or frozen.  Which valve do you think it might be?