| Author |
Message |
Doug Dickinson (Dougd470) (24.207.251.176)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 02, 2003 - 7:03 pm: | |
I have a problem that I am hoping you folks can help me with. I am posting this on the MCI board and the Busnut BBS also since some of the knowing lurk there and not here also.
I have a ‘83 MC9 NJ Transit version. A week ago, the R-8 rear brake relay valve died and I had to get someone out to help me get the coach out of the road and back into the parking area at the storage yard. With the drive brakes released, I coaxed the coach, dragging brakes, the couple of hundred feet back to the parking space with the suspension down and no air pressure.
The brake relay valve was replaced (what a nasty job THAT is) and now, the brakes are acting a little different. When I release the parking brake, the brakes do not release immediately. The brake light on the idiot light display stays on for about a minute, then after a couple of minutes, the brakes slowly release and the coach ill roll. When I apply the service brake, the same thing happens – the light stays on for a minute and then goes out and about 2 minutes after that, the brakes release. The service brake is also stiff, as if the E-brake were still engaged.
Now for another issue that may be related – when I air the bus, I raise the front of the bus (it has a kneeling feature) and when I do, the front leveling valve is acting strangely – It is acting as if air is going into the suspension and the leveling valve is seeing an over-inflation and bleeding air to lower the front. I also cannot make the bus kneel, which is new also – as if a valve is stuck.
Now – my suspicion is that the problem I am seeing now is that there might be some kind of interlock in the kneeling system that is causing the problem, but I don’t know where it would be. The book doesn’t show a kneeling system for the coach and I am REALLY DUMB when it comes to air brake systems. Anybody know what could be causing this? |
TomNPat (66.82.9.38)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 03, 2003 - 2:18 am: | |
Try grabbing the brake pedal and pulling it up. Had the same problem on my NJT and the rod had rusted, not letting the pedal return freely.
If the pedal is down 1/4" at the top, it will apply some brake pressure. Not sure that the rest of the linkage may have some rust too. We only get 88" of rain on the average and that New Jersey salt is allergic to that much water.
Hope your problem is as simple as ours.
TomNPat |
Buswarrior (Buswarrior) (64.229.211.211)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 04, 2003 - 12:11 am: | |
Hello Doug.
I'd be concerned about what caused the R8 to fail. Any junk in the lines? Because the other parts upstream may have been in similiar condition, and have failed concurrently.
Also, in the process of trying to get the coach recovered from the street, something else may have been damaged or disrupted.
You didn't indicate how you got it to roll off the road. Are the mechanical parts at the wheel ends returned to proper configuration and undamaged?
Before going crazy, I expect that you have confirmed that your replacement valve is truly an R8 and not something else, and that the lines were faithfully attached in the proper ports.
You didn't indicate how you knew it was the R8 that had failed. Have you replaced the right valve? Is the Inversion valve functioning properly?
You are practicing proper DD3 parking brake release procedures? Aired up, push the control in, and make a full service brake application?
Are the dash lights indicating reality? Are the pressure switches full of gunk, and you've really got proper brake functionality underneath?
Better head underneath and start tracing where there is air and where there isn't and whether that is right or wrong for how you have an assistant upstairs configure the controls.
Is air quickly exhausted out the bottom from the R8, the front quick release valve and the brake pedal valve when the service brakes are released?
Remove one line at a time and see what's leaking through where, and where the air is being obstructed and whether that is right.
Be sure to block the wheels and don't pick an assistant that owes you money!
Let us know what happens!
happy coaching!
buswarrior |
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