| Author |
Message |
John (152.163.188.227)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 27, 2002 - 12:03 am: | |
In a MCI drivers manual, it saids that the service brake should not be applied prior to the release of the parking brakes. It saids that this will result in overpressure and risks damaging the lines, seals. Now in most bus manuals, it saids to make a full service application prior to the release of the parking brakes. They don't mention anything about overpressure.
Is this just the design of the brakes on MCI models? I see drivers do both. I also seen drives release the parking brake then put the bus in gear, without using the service brakes. Is there a "proper" way? |
RJ Long (24.127.74.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 27, 2002 - 1:37 am: | |
Depends. . .
If the coach is equipped with spring brakes, then no service brake application is required when releasing the parking/emergency brake. (Altho it's a good idea to lightly cover the service brake in case the bus starts to roll unexpectedly.)
If the coach is equipped with DD3 brakes, then you must make a full service brake application in order to release the parking/emergency brake.
MCI's manual is right: you DON'T apply the service brakes fully while the parking brake is applied. The procedure is to cover the service brake lightly, push down on the parking brake button to release the brake, wait one or two seconds, then fully apply the service brakes for a couple of seconds, and finally, release and cover the service brake to prevent the bus from rolling.
How do you determine which type of parking/emergency brake YOUR bus has? Simple. With the system's air pressure built up, put the transmission in gear, lightly cover the service brake, and release the parking brake. If the bus starts to roll (auto trans), you've got spring brakes. If it doesn't roll, and a VERY tiny bit of throttle doesn't cause movement, you've got DD3s. Try a full service brake application to confirm.
(If you have a manual gearbox, a "DTS" will help you determine the brake type. What's a DTS? Go over to the Articles of Interest section of this BNO website and read "Shifting. . .")
HTH,
RJ
PD4106-2784
Fresno CA |
joe shelton (Littlewind) (165.247.5.111)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 30, 2002 - 11:32 am: | |
OK now I know I don't know what I've got. Aren't spring brakes the type that are applied under spring pressure when air pressure is 60psi or less?
Some times (about 1 out 5) when I release the parking/emergency brake (by pulling up on the knob) they don't release and the bus wont move under throttle. So now when I apply the parking brake I make sure my foot is off the peddle, and I try to keep from applying peddle until I release the parking brake.
The cans say mini maxi on them. |
DaveD (64.235.200.81)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 30, 2002 - 5:41 pm: | |
With DD3 brakes you need to fully apply the service brakes for about 5 seconds to release the parking brakes, I usually wait until air pressure in the ystem is up to about 120 pounds (the air dyer usually purges around this pressure by a signal it receives when the governor cuts out the compressor. MCI's operator's manual states that if this fails to release the brakes, to pump the pedal to reduce the pressure to under 75 pounds, wait for the pressure to build up to at least 100 pounds and try again.
DaveD |
Tom Caffrey (Pvcces) (64.114.233.195)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 31, 2002 - 12:05 am: | |
Joe, spring brakes, DD3 and minimax all are supposed to self apply if the pressure drops too low.
If the cans say minimax, you should need to step on the brake pedal fairly hard after placing the knob in the released position. This will only work if you've got air up.
Sometimes, they get crudded up and have to be dismantled and cleaned up in order to get them to work reliably.
Tom Caffrey PD4106-2576 |
joe shelton (Littlewind) (165.247.14.123)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 31, 2002 - 11:00 am: | |
Thanks Tom, I understand Minimax are no longer available and parts are hard to find. Should I be gathering new cans for replacements and, if so, what would be a good choice. Joe |
Tom Caffrey (Pvcces) (64.114.233.21)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, December 31, 2002 - 4:52 pm: | |
Joe, a lot of people used Minimax because there was not enough room to mount the spring brakes on the GMs. I understand that they're not too hard to clean up, so why don't you look at that, first.
Even though they are not available new, I think there are quite a few used ones around. We've even got a pair here that we're not using.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
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