| Author |
Message |
Nick Russell (66.82.9.26)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 13, 2004 - 11:29 pm: | |
While driving from Alabama to Kentucky today, I got into a couple of spots wehere I had to stop for traffic or a signal light, and each time my air pressure dropped down to the point whewre my brakes locked up and would not release until I put the MCI 8 in neatral, set the emergency brake, and reved the engine up to build pressure. Once I got up to about 110 pounds (it builds air pressure fine and as fast as always), the brakes would releasle and all was well. Going down the highway there is no problem, air stays up to about 120 pounds. Wen I arrived in Bowling Green, Kentucky, and pulled into my destination, a good sized oil puddle formed under the right rear end of the bus, and again the brakes locked up. I'm thinking it's the air compressor (though it builds pressure fine, even with just high idle on), or a broken air line. Too dark to see much tonight, but when I looked in the right engine compartment side door, a lot of oil all over everything. Any ideas where to start looking (ok, I know where, but what to look for)? No obvious sounds of a broken air line. |
joe shelton (64.222.182.103)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 14, 2004 - 8:03 am: | |
i've had breaks lock-up while @ low idle in traffic caused by low air pressure. it was the governor; easy to replace for $20. But the oil I can't figure. If I remmember correctly, oil is supplied the compressor via an external oil line and returns to the engine thru the compressor sump. But compressor output souldn't be effected by oil starvation. Now if your compressor rings were shot (which mine are due to over heat of compressor), they would pass oil into the air system or they may allow the compressor to pressurize the engine sump. Bad rings may be the source of your oil on the ground & low compressor performance. |
TWO DOGS (63.185.97.20)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 14, 2004 - 9:12 am: | |
how much engine oil did you loose...how long from the first time you noticed something wrong till you arrived at your destination...could be something as simple as your govener comeing loose to as complicated as you need a new engine...it should be easy to find something in 'daylight'...call a truck repair shop if you can't find a 'bus' place in B.G. |
Captain Ron (207.30.240.57)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 14, 2004 - 9:26 am: | |
What ever you do don't go to kenworth of bowling green. They charged me $1570 for labor to install a trany in my 4905 after quoteing me $650. There is a bus shop about 40 miles south in lafayett tenn. that treated me fair on parts i needed and even let me do a repair my self with his tools.He has huge inventory.the info for that shop is at my bus but if you need it call me #239-292-1750
Good luck |
mel 4104 (208.181.100.104)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 14, 2004 - 10:12 am: | |
if your air presure builds up reral quick and drops the same way it could be your gov. . as on other posts check and make sure that your air tanks are not full of water and oil. also check you air brake valves to see if there is oil coming out of themas when they get oil in them they also will cause trouble. be sure that you post what you find is the trouble so others can use the infomation .. |
Buswarrior (Buswarrior) (64.229.211.226)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 14, 2004 - 9:58 pm: | |
Hello Nick.
I am intrigued by your problem, or should I say problems.
I wouldn't be in too big a hurry to associate the oil leak with your loss of air pressure right away. You may just be having the bus converter's law coming into force: "When any failure is iminent, another system will fail simutaneously in sympathy, in order to confuse the owning busnut and all of his/her sources of reference."
Did the air pressure drop away when the brake pedal was being held down, or when you had consumed enough air pressure that the compressor should have been cut in to replenish?
The fact that air pressure restored normally with the parking brake applied, suggesting you weren't holding the brake pedal, makes me wonder if you have a leak in the service brake circuit somewhere, popularly a brake chamber diaphragm, or a valve with deteriorated internals leaking out the vent holes.
Also, not to be ruled out is the fun that the DD3 circuits present.
If you are able, would you add some more details to what you experienced and under what conditions?
happy coaching!
buswarrior |
DaveD (24.58.141.49)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 14, 2004 - 10:13 pm: | |
I'd suspect a leaking DD3 brake chamber. MCI sells rebuilt chambers on an exchange basis for about half the price of a new one. These are fully guaranteed and have new shells and diaphrams as well as any other internal parts that need replacement. Basically they will ship you one and refund the core charge once you return the old one. They sent one overnight and that solved a very similar problem.
Dave Dulmage
(MC-8) |
Nick Russell (66.82.9.28)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 15, 2004 - 11:47 am: | |
Thanks for all the input, guys. Right now I am at Life on Wheels in Bowling Green as an instructor, and every minute is occupied until this ends Monday afternoon, so it will be then before I can do anything. From everyone I'm talking to, I think it is indeed a brake diaphrahm. The air pressure loss only occurs with the brake pedal pushed down, like sitting at a stoplight. I drove 200 miles the day this happened, all on the interstate and did not have any problems while going down the road, slowing for merging traffic, etc. The problem is only when I got off the highway and hit some traffic lights, where I had to come to a complete stop and hold the brake pedal down until the light changed. I checked the engine oil, and it is full, so whatever oil I lost when I stopped was not a huge amount, though the puddle was pretty big, maybe 8 or 10 inches across. I'll keep you updated. |
joe shelton (64.223.182.47)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 15, 2004 - 8:52 pm: | |
Nick, keep in mind that you can loss enugh pressure at low idle due to a falty governor. That is exactly what happined to me while stopped in traffic with brakes applied. $20 later I was back in service. I suggest you replace the gov and then see what happins because its cheep and eezzee to replace. IMHO joe |
Buswarrior (Buswarrior) (64.229.208.164)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 16, 2004 - 9:56 pm: | |
Hello Nick.
Air up the bus, put an associate in the seat, shut off the motor, release the parking brake, have associate hold down brake pedal, and go outside and listen.
You may have to air up again, if the leak is heavy enough to drain the tanks before you close in on the problem.
This will only cost you the price of the diesel to run the air up,and then you'll know where it is leaking.
Get back to us and let us know, if it starts looking complicated again!
happy coaching!
buswarrior |
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