| Author |
Message |
James P. DeHaven (Boneofjoy)
Registered Member
Username: Boneofjoy
Post Number: 1
Registered: 10-2006
Posted From: 68.201.148.134
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 12, 2006 - 8:05 pm: | |
Can anyone help in solving an air leak in my MCI 8? It seems that when the emergency brakes are applied via the push-pull valve, air leaks out the exhaust port of the R-8 relay valve. The emergency brakes work as do the service brakes. The problem is that it takes forever to air up past the 90 PSI required to release the emergency brakes(and then I have to run 1800 RPM to get above the 90 PSI). Once past the 90 PSI point, I can release the brakes and everything works fine. I've replaced the R-8 valve to no avail. No leaks at the push-pull or the service valve. Could this be the inversion valve? Thanks in advance. |
Buswarrior (Buswarrior)
Registered Member
Username: Buswarrior
Post Number: 916
Registered: 12-2000
Posted From: 67.68.35.64
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 12, 2006 - 8:54 pm: | |
Hello James.
I suspect that you have a leaking parking diaphragm in one/both of your DD3 brake chambers.
The parking diaphragm, if ruptured, will let the air pressure applied to park leak through into the service brake cavity. From there it will exhaust through the relay valve.
When you push in the parking brake valve, there is no pressure applied to the parking diaphragm, and the leak stops.
Diaphragms are relatively inexpensive, and since you have to get in there anyway, you might want to change all 4, service and parking, and then it is done.
If on a budget, once you are under there, have an assistant manipulate the parking control, if you are lucky, you might be able to hear which chamber is leaking, otherwise you have to remove air lines and plug to see which one is guilty
Don't worry that you have changed the R8, that's just more good preventive maintenance.
And, just to break the bank a little more, since you'll have to access the area anyway, you may want to consider changing out the inversion valve, its pressure regulator and the flexible air lines as part of this maintenance you are already doing.
After that, there's nothing left, brake plumbing wise, to go wrong back there for quite a lot of years!
I have found that removing the wheels, putting the axle on blocks, and blocking the suspension gives good access in through the wheel wells.
A sawzall is a handy tool for removing the inversion valve, cut the locking nut off from above and chisel it out.
happy coaching!
buswarrior |
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