MCI 102c3 6v92ta Mechanical Won't Air Up

[Jcparmley]

You mean when I press the brake pedal?  Yes, I hear air escaping.  I bet the shoes are stuck on the drum.

Takes at least 85psi to release the DD3 brake lol 120 psi is better,the DD3 chambers need to vent the air to release can you hear escaping air ? if so then the shoes are stuck on the drum

[buswarrior]

Again, never mind the distractions.

Find and stop the leaks.

It isn't moving without proper air pressure.

Full stop.

happy coaching!
buswarrior

[chessie4905]

Here is a lengthy post from a few years back. Slow reading to comprehend, but should help. Also download the Bendix air brake manual pdf. Available in several locations on the net. FREE!

https://www.busconversionmagazine.com/forum/index.php?topic=31316.15

[luvrbus]

You mean when I press the brake pedal?  Yes, I hear air escaping.  I bet the shoes are stuck on the drum.

No when you push the PBV in you should here air coming from the DD3 chambers if you have air pressure leaking when you push the pedal down means you have leaks,pushing the pedal down with the right psi releases the rachet locks on the DD3 brakes when let the pedal up then you hear air.The inversion valve BW keeps talking about on DD3 brakes controls the rachet locks on the DD3 that is the valve only purpose those are easy to check or clean look on the Bendix site and there you can see the valve to help you identify it,The rachet balls will rust and old grease build up will cause those not to release, the chambers have grease fitting try pumping new grease when you get the right PSI.? did the bus have that many leaks when it was parked 

[tr206]

I do not have 120 psi.  What I meant is I have enough pressure that break release button stays down and doesn't pop back up.  I thought the parking brake only needed 85 psi.  It has been sitting for over a year in it's current spot.  I don't know how old the valve is.  I never changed it.  I will keep chasing down more air leaks until I can get 120 psi or the air dryer purges.  I was hoping to release the brakes and move it closer to my shop so I can track down more leaks.  Right now its a couple hundred yards from my shop.  I wouldn't be surprised if the brake's are rusted to the drums.  Any clever way to break them free?

Any clever way to break them free? 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!

[Jcparmley]

When I press the brake pedal I only hear air when I lift it up.  I did not notice many leaks when I parked the bus.  To get to the grease fitting do I need to jack the bus up and block it?

No when you push the PBV in you should here air coming from the DD3 chambers if you have air pressure leaking when you push the pedal down means you have leaks,pushing the pedal down with the right psi releases the rachet locks on the DD3 brakes when let the pedal up then you hear air.The inversion valve BW keeps talking about on DD3 brakes controls the rachet locks on the DD3 that is the valve only purpose those are easy to check or clean look on the Bendix site and there you can see the valve to help you identify it,The rachet balls will rust and old grease build up will cause those not to release, the chambers have grease fitting try pumping new grease when you get the right PSI.? did the bus have that many leaks when it was parked

[robertglines1]

what part of the country are you???   Maybe someone hands on can help..   Looks like your learning system under fire--you won't forget it!  Spray bottle with dishwasher soap and water is your friend. squirt and look for bubbles. You have the best trying to help so be patient...my last mci 1978 had air beams rusted out.. used block off plates to solve problem. I am not famiular with the 102c3..

[luvrbus]

The bus is dual air system watching the gauge should narrow his search when checking for a leak where the leak is on the rear or front of the bus,If he has field mice those love the taste of the DOT plastic lines and wiring for dessert

[robertglines1]

yep on mice.. had one chew  airline in tunnel. someone had bright idea to use soy oil in process. didn't last long.

[Jcparmley]

I live in just west of Madison Wisconsin.  My bus only has one air gauge and only one needle in the gauge, so I can't tell what the pressure is in the rear and front separately.  We do have field mice. 

The bus is dual air system watching the gauge should narrow his search when checking for a leak where the leak is on the rear or front of the bus,If he has field mice those love the taste of the DOT plastic lines and wiring for dessert

[luvrbus]

When you are airing the bus up does it reach about 60psi at a steady pace then slows down ?

[robertglines1]

JC :went  to  college in madison and met first wife there. About 400 miles south of you now.  We have members in that area.. Hopefully one of them can lay hands on.  Made that 402mile trip a bunch of times.  Check your aux air tank in steering compartment. the bottom of those seem to rust out and are hard to detect. Some will cringe at this suggestion.  Or throw things at their computer. Try introducing Air tool oil into where you are providing aux air.  It is hell on air dryers but at this point it might just free up a stuck valve. Knowing where you are helps understand possible ice in lines etc. Has any thing improved with this brief warm up? BW and LV bus understand cold and have massive experience with air systems..In bus & equipment..Will continue to monitor progress..Bob

[Jcparmley]

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.

[dtcerrato]

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.

I wouldn't count on finding almost any leak by trying to feel sir with dry hands. It would have to be a massive leak to feel.it that way. On the other end of the scale a slow leak could take many minutes to show up under soapy solution. Just saying.

[tr206]

Make sure you spray soapy water on any aeroquip hoses the hose itself especially the old hard ones air will bleed through without you hearing or feeling it. Had a air leak I could find for over a year when I hit the air line with soapy water the whole line foamed up (hose).