Stubborn Air Presure

[AJ]

My MC8 developed not so good habits recently during the cold eather.
The air pressure reaches around 85 to 90 in less than 10 min. But it takes foreever to pass 90 psi, and be able to release brakes. This morning it took 35 min. to release brakes. Once it release the brake and hit the road, it runs all day without problem by cycling between 90 and 110 psi.
My question to you is how can I kick the bad habit?

AJ

[bevans6]

The air system is separated into two halves by the air protection valve, which normally is set to around 65 psi.  It ensures that just the brake system is pressurized as the first priority, and only after  the brake system is at 65 psi does the emergency brake and the auxiliary system begin to pressurize.  Your system is going a bit higher than 65 before it slows to fill the rest of the system, but still the difference suggests that the issue is the suspension system, fed as part of the auxiliary tank system.  Is your bus losing air in the suspension and settling down on the bump stops?  If your bus is losing air  pressure in the suspension, and then having to completely refill from scratch, it can take a long time, particularly if there is a leak, or other issue in the levelling valves.  Test this - how long does it take for the air system to fill from 85 psi to 100 psi if you first allow it to fill completely then fan the brakes down to 80 psi and allow the compressor to work?  If the compressor is working properly, it should take between 20 and 40 seconds.  The DOT test is 2 minutes, but if it takes longer than 40 seconds, you do have an issue.  If it recovers in 30 seconds or less, the air compressor is working properly.  Then, turn the engine off and watch the pressure gauge.  It shouldn't move so you can see it in three or four minutes at least.  No discernable pressure drop.  Then do a full brake application, and watch while timing for one minute.  The maximum  allowable drop is 3 psi.  If you pass those tests, then your suspension is probably at fault, I would suspect moisture in the system.  how often do you drain the tanks?  All the tanks, all the way down?

These are just the first thoughts that occur to me, I hope they help a bit!

Brian

[buswarrior]

Something is leaking. The cold makes leaks worse.

Try shutting off the air supply to the shutters, old seals in those leak like sieves in the cold.

Otherwise, check the exhaust ports on your brake valving, and the leveling valves.

happy coaching!
buswarrior

[bobsw]

My bus was having the same problem. I had a leek in the air protection valve. I took it off and took it apart and cleaned the gunk out of it put it back on no more problem.

[gus]

My air suspension always leaks down a lot faster in cold weather.

I've seen a few reasons for this posted but not really sure I understand it yet??

[robertglines1]

mine does also...was told it was because of contraction in fittings in cold weather I just know when it warms up my air stays up days instead of hours..

[AJ]

Folks,

Thank you for all your good comments and advice.
I truly appreciated.

AJ

[gus]

After starting during a very cold morning recently I noticed one of my rear leveling valves was leaking so much that I could hear it 30' away.

It soon stopped but gave me a bit of heart palpitation!