MCI brakes

[cmdahl24]

We have an 87 MCI 9 with air brakes and when my husband quickly applies the brake repeatedly 5-6 times the air pressure drops dramatically.  He would like suggestions on what could be causing this.  He would have asked himself but his request to join has not yet been approved.  Thank you in advance for any information.

Carmen M. Dahl

[luvrbus]

They work that way most will drop 10 to 15 lbs with the first brake application,takes a lot of air to fill the brake chamber each time 

[Tom Y]

How much is the air pressure dropping? Does it continue to drop if he steps on it and holds it down?

[Dave5Cs]

And on the other side of the coin how long for it to fill back up to 112-120Lbs. Do a Brake application so that the air pressure once fill travels down to 80 Lbs. then time it to see if it goes back up it 100lbs in about 45 seconds. Brake test.

[Lee Bradley]

Another cause is the brakes being out of adjustment.  The farther the cylinder travels the more air it takes each stroke.

[gumpy]

... when my husband quickly applies the brake repeatedly 5-6 times the air pressure drops dramatically.  He would like suggestions on what could be causing this. 

Just going out on a limb here, but I suspect the cause of the pressure dropping is due to him stepping on the brakes 5-6 times. That's how they work. The pressure used to apply the brakes is released to atmosphere when the brakes are released, not recycled back into the system.

Sorry there's just not enough information in your question to diagnose it from my armchair. 

[Utahclaimjumper]

  DRAIN THE TANKS!!  Water and oil in the tanks will displace air,, then you don't have the voluum that you need for multiple applications.>>>Dan

[Geoff]

I, too, wonder why he has to "stab the brakes" 5-6 times.  The only time I ever do that is to slow down going down a hill, and now that I have Jakes I don't even do that anymore.

--Geoff

[bevans6]

He's probably just sitting there fanning the brakes and wondering what is happening.  I hate when people who have very limited understanding of air brakes first get a bus.  It really is one of those things were if you don't know about it, you should learn before you play with them.  It's one of those things where taking a class is a good idea.  The air system of a bus is a fairly complicated thing to figure out on your own.

[Geoff]

He's probably just sitting there fanning the brakes and wondering what is happening.  I hate when people who have very limited understanding of air brakes first get a bus.  It really is one of those things were if you don't know about it, you should learn before you play with them.  It's one of those things where taking a class is a good idea.  The air system of a bus is a fairly complicated thing to figure out on your own.

Now,  now, he was just just doing the bleed down/recovery test but only knows the first part part.  Or maybe the bus failed the air recovery test and we are giving him good advice.  After all, we are getting the story second hand from his wife.

--Geoff