| Author | Message | ||
| Tim C. (205.118.9.14) Rating: |
First: Thank you, Ian, for the time and money you put into this board. I appreciate your altruism. Second: Thank you, Luke, for helping us stay out of harm’s way and contributing your wisdom. I hope you see this post and have time to respond to my problem. Third: Thank you to everyone else who contributes to this board. I appreciate all the different points of view and your willingness to share your insights. It is also cheap entertainment!!! And, fourth, to the problem: I have an MC-8 I have not started for about two months due to dead batteries. I have purchased an excellent three-stage battery charger that is hard wired into the charging/starting system, which has resurrected the batteries that I thought were dead (but that is another story). I started the bus on Saturday but the air gage on the dash would not move off of zero. The automatic pressure release valve kept releasing pressure so I know the air compressor is working. The brakes also had pressure because they would apply and release when I pushed and released the foot pedal, however the DD3 would not release. My future plan is to take apart and clean all the parts of the air system, but right now I just want to fix the immediate problem. There are multiple tanks and valves in the air system and I am thinking that one of the valves is stuck shut. It could be frozen because we have had some below 30-degree weather. Could someone suggest the specific valve or part to check first? If I can get the bus moving I can pull it up on some blocks in order to do a more through cleaning and repair of the system. Thank you for your help, Tim C./MC-8 | ||
| DaveD (216.18.113.69)
Rating: N/A |
I had a similar problem on my MC-8 when the temperaure dropped after I had I parked it in the fall. I think there was moisture in the system. I was unable after a number of tries over a few weeks to get the brakes to release. When we had a series of mild days I started the bus up and once pressure was reached I was able to release the brakes. Check for a leak at the relay valve R-8 which, if I recall correctly, is located on the bulkhead at the rear of the luggage bays. You can probably hear it leaking from the area between the drive wheels when the service brakes are applied. You need to have the bus blocked if you want to do a closer examination as you will need to crawl under the bus. Hope this helps. | ||
| HenryMC7 (24.70.95.206)
Rating: N/A |
When the engine is running it is hard to hear some of the leaks.(BTDT) Try airing up your bus with an air compressor. If you use a 50' hose and keep the compressor away from the coach itself, you will have an easier time hearing where the air is coming from. When it comes to dealing with frozen air lines, there could be a blockage almost anywhere. I find it interesting that you say you have air pressure at your brake pedal, but the gauge doesn't register anything. I don't have anything to offer for that, but I had a leak right on the DD3 pot itself and it wouldn't release the parking brake even though there was lots of pressure everywhere else. It was about -5F. I ended up brushing off some ice that was on the brake pot. The air stopped leaking instantly and the brakes released. After you do figure things out, you might want to push some brake-line antifreeze through the system to remove the remaining moisture. Henry | ||
| Mike Stabler (Docdezl) (64.255.109.144)
Rating: N/A |
Tim sounds like your making enough air you might try to hold down on the release knob with the engine at high idle to get her on blocks. OR hook up your shop air up to the wet tank. OR both. Now with your heat gun/propane tourch/moma's hair dryer. Apply heat to leaking valve. Probably the drain valves (on bottom) or,the presure releif valves (near top)of tanks. Ice and or frost does wierd things to valves that are only supposed to see air. Too much heat on anything get the ####'s and call Luke! Suggestion:: Check truck bone yard for the newer spin-on type air dryer. If I lived in Death Valley I would still have one. Keeps the oil with (some acid) moisture with (shmoooz?)and stuff (its a filter) out of your system. Side bar:: When the trucks started comming into the fleet with them (AD2's) the number of shelves for air valves in the parts room whent from 10 to 2. Hmmmmm ? smoke,rattle &,stink....docdezl | ||
| Luke Bonagura (Lukeatuscoach) (12.90.12.78)
Rating: N/A |
Hi Tim: Yes, I have read your post and thank you for your "kind Words". It is my pleasure to Help as time permits. I read this & other Boards daily and they provide a tremendous education for me, as the problems you, as converted coach owners experience, is often different than what our commercial bus operating customers experience. I really enjoy the way you folks cheerfully help each other. It is the old fashioned American/Canadian way of People Helping People!! I commend you all!! It does not take much moisture in an air system to cause the problem you have. There is no way to pinpoint where the frozen water is. If your weather has improved to where you are above or just around freezing, then the following might apply. If you are consistently below freezing day & night, I am afraid you will have to wait for better weather. From what I read, you can not SAFELY get under the coach, so here is one suggestion that may possibly get the coach going for you. By the way you mention "The automatic pressure release valve kept releasing pressure". I am not sure what you are referring to?? Do you have a spit valve on an air tank or an air dryer?? Not all MC-8's were built with the same equipment, so I hope you understand the reason for my question. Now my suggestion, and what we are trying to accomplish is to get warm air from your compressor through the entire air system: Start the bus and let the air build until you hear the air pressure release that you mention. At that point, pump your brake pedal, until you don't hear any more air exhausting from the brake system. Let the air build up again until you hear the air pressure release. Continue this & hopefully the air gauge with start to rise. At that point you now have air coming to the front of the coach and you will know if there is enough air pressure to release the DD3's. It generally takes at least 90lbs of air for them to release, but in this case I would try to get up to the 90 to 120lb range so you know what pressure you are supplying to the rear chambers (Hopefully). I Hope this Helps and if you need additional help, E-Mail me by hitting on my name at the top of this post & we can go further. I Hope this HELPS!!!! LUKE at US COACH | ||
| ChineseElite (24.68.144.216) Rating: N/A |
Interesting one here.... We ran into this problem (and another) on a 96 102DL, with a 12.7 litre DD S60... Anyways, the pressure would build up to about 70 to 80 PSI, and stay there. The governer in the rear was spitting like mad (well, at least by usual standards) and we couldnt get enough pressure to release the parking brakes until we got shop air in the tanks... What happened was a little bit of moisture had frozen up a line (it was -30°) somewhere, and a night indoors cleared that up.... However the problem was still there! Got the bus the next day, and managed to drive it to another shop (we were at the DD shop in Edmonton, Waterous) and have them take a look at it... After doing some collective thinking between the mechanics, they discovered that the air compressor had a bad seal... BTW if you are ever in Edmonton and need work... Buses 'R Us is a great place... they know what they are doing. | ||
| Earl-8-Ky (207.162.163.19)
Rating: N/A |
I have a MCI MC8. I had a problem with mine that is very similar to yours. It would not build enough air to relese the brakes. It was the air governor on the air comp. Very easy to replace cost about 25$ Hope this helps. | ||
| Gene Jorgensen (Geno) (172.135.209.4)
Rating: N/A |
I too have that problem on my MC7. My air is leaking from between the front wheels. I believe it is at the air leveler for the front bags as I can not build up air in the suspension. Did not have this problem before the cold set in. I guess I will do as Luke said and wait for warmer weather. | ||
| FAST FRED (209.26.115.42) Rating: N/A |
If the batterys were really DEAD for a month or two , you should plan on early replacement. Recharging will bring the volts back , but only a small percentage of the standaed amperage will be back. FAST FRED | ||
| Pete (205.188.209.11)
Rating: N/A |
My 4501 does the exact same thing..mine just like most other GMC's will not shut off if there isnt a certin amount of presure..There is an air chuck somewhere you can load the bus up to preasure..I've been told that will release the breaks. Mine is frozen..I know it..its 50 some years old..taking it appart isnt an option for me..I purge all the tanks in the summer when its warm and when I put it to bed for the winter...one of these days I'll get an evaporator in there.. Till then..IT..will be as cold as I am..lol Pete | ||
| Jerry (152.163.188.227)
Rating: N/A |
Alcohol flushing -- I've heard or read about some proceedure to flush the air system with alcohol from the compressor on -- helpes remove the water, oil, and debris. Maybe someone more familiar with this possibility or proceedure can fill us in with the details. | ||
| Luke Bonagura (Lukeatuscoach) (12.90.1.172)
Rating: N/A |
Hi Jerry: When we were operating buses, we had alcohol evaporator kits on all of our older units. Quite frankly, I liked them better than air dryers, as they do not require any maintenance other than keeping the reservoir filled with alcohol, and keeping the "Wet Air Tank" drained. It is a very basic system, developed by Bendix for their air systems. Each time the compressor cycles, the evaporator shoots a measured amount of alcohol into the air system. The alcohol collects water, sludge etc. & sends it to the wet tank. We sell & install many of them in our shop. If you want more info., hit on my name at the top of this post & I will get back to you. I Hope this HELPS!!! LUKE at US COACH | ||
| Tim C (66.219.221.25) Rating: N/A |
Thank you everyone for your help. Bus is running again! |
