| Author | Message | ||
| Cameron Jones (Crazy71)
Registered Member Username: Crazy71 Post Number: 3 Registered: 12-2006 Posted From: 75.179.158.67 Rating: N/A |
I had a freeze up in my mc-8 a few weeks ago. It was fine all last winter. I had to put a heater under the front and in about 20 minutes it was ok. I had air to the brakes at first...then my dash gauge went above 125 and I had no air anywhere else. It wouldn't shut down the engine, even by the emergency flip one. I had to manually flip the damper thing in the intake. After I started it back up...the brakes were getting no air either. After I heated under the front up all was ok. I had just filled the can in the right rear door with alcohol 10 days before and it was still really full so I don't think it is working. How do I check the alcohol system. BTW this is the BEST bus board I have ever seen. I have read posts here for years. I looked for 7 years before finally finding a bus I could afford that would make it home. You guys are great!! | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 364 Registered: 10-2003 Posted From: 71.58.126.56 Rating: N/A |
I checked * Bendix alcohol drier * on the web for info and found out that Bendix no longer recommends the use of alcohol or other substances in their brake systems as it causes gradual deterioration of the seals in the brake systems. They now recommend the use of air driers, which after I installed one, I agree with them. The Bendix brake handbook only says that the alcohol is to be introduced into the air compressor air intake system, probably through an orfice from the bottle; may be plugged? Also, if the bottle has been empty for awhile, it may take a few miles to get the alcohol through the system. Even the initial installation of an air drier takes a while to purge all the moisture.If an air drier is too costly at the present, you could install a moisture ejector, as they are pretty cheap and easy to install.Do a search on the web for the alcohol drier for possibly more info. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 960 Registered: 12-2000 Posted From: 64.228.88.36 Rating: |
Hello Cameron. Unfortunately, Prevention through good maintenance is the critical component to proper functioning of an air system in sub-freezing temperatures. You have to keep the air system dry, not allowing it to get poluted. Alchohol applied after the fact is a stop gap strategy at best, and the reliability of that air system will be suspect whenever temps go below freezing. Fear not, with some work, you can recover the system! Some background: The moisture that causes the actual performance problems is in the valving. It freezes seals against their mating surfaces, and freezes moving parts. The surface area inside the valves is not sufficient for the applied air pressure to break the bonds that the ice crystals make. With it usually only ice srystals, a small amount of heat will temporarily return things to functionality, as you have found. And take note that the methods popularly employed by truck drivers pouring the alchohol into lines and tanks doesn't necessarily fix stuff that is already frozen. The anti-freeze has to be mixed with the moisture to prevent freezing, it is not a de-icer. The saving grace may be that the alchohol came out of the cab of the truck and is already warm. Pouring warm water into the truck would have accomplished the same short term goal of unfreezing what was stuck. If you were wondering about alchohol consumption, an alchohol evaporator does not empty very quickly. According to Bendix, 1-2 ounces are consumed for every hour of compressor run time. That's compressor running, not engine running. For a system that is already poluted with moisture, it is hard to get the alchohol "inhaled" deeply enough to start mixing with it and lowering its freezing point. And an air dryer is only capable of drying some 10 cubic feet of air and then it starts to pass moisture into the system. The air system must be allowed to reach cut-out periodically so the dryer may purge the accumulated moisture. So, for a thorough fix: You will need to blow out of all lines and valves with clean dry air, in an above freezing environment. The whole system will be damp inside. We hang wet laundry on the clothes line on a dry day to let the breeze dry them. Same concept. Warning: Using the shop compressor without a good moisture trap in the line is only introducing more water. Use the bus compressor. On a warm day, or into the heated shop.... If you have an air dryer, service it. New desicant and confirm the heating element is powered and working. Consider seriously installing one. See the wrecking yard near you for a good used take-out. Alchohol evaporator must be plumbed downstream from the dryer, not the other way around. Alchohol turns the air dryer desicant into ineffective mud. Ensure all your air tanks are empty of moisture and contaminants. A pond in the bottom of a tank creates a humid environment, and the humidity is what freezes seals in valves. Run the bus, use its own air compressor, confirm alchohol evaporator functioning, it should bubble lightly when the compressor is pumping. Open wet tank drain and let it blow with compressor running for a few minutes and then close. Let the air dryer purge. Move on to the next tank and let it blow for a few minutes, then close it, let the dryer purge and so on until the tanks are all containing fresh, dry, anti-freeze laden air. Now, fan the brakes repeatedly, again, taking the system up and down a few times to be sure that there has been lots of the afore mentioned anti-freeze laden air blowing through all the valves, displacing and mixing with whatever moisture may be there. Run the air wipers. The suspension is a trickier nut to crack, but there are far fewer reports of suspension related freezing issues than there are for brake valves. I might leave it alone and hope for the best, unless you want to mess with disconnecting the leveling valve arms and manipulating them to get air flow. let us know how you make out! happy coaching! buswarrior | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 79 Registered: 10-2006 Posted From: 206.149.192.28 Rating: N/A |
Most alcohol setups have a small shaped plug on the top of the jar. When its IN the vacum of the compressor can not get suction. When its OUT, not sealing the jar , the alcohol can get to the system. This "stopgap" was the standard of the world trucking system for 50 -70 years or so. Now for a for a few hundred bucks , and a few hours of annual maint , plus parts , you can get "modern". For most bus campers that flee winter , a questionable use of time and currency. FF | ||
| Cameron Jones (Crazy71)
Registered Member Username: Crazy71 Post Number: 4 Registered: 12-2006 Posted From: 152.163.100.138 Rating: N/A |
Hi Fred. Mine does have a plug, but it is a 1/2 inch or 9/16 hex. I think it is just the fill plug. I took the aluminum housing off its mount. Three bolts hold it on. It does have a vent to the rear of the flat mounting pad. I think this is where it is vented as you mentioned to get its suction. This hole was pretty covered up with dirt and junk. I blew it all out and put it back together. Hopefully it will pull alcohol now. This is a 77 MCI-8. This is the factory add on system as pictured in my MCI service manual. Thanks to Buswarrior for info on the need ro bleed a lot of air to purge water out of system. All the tanks confuse me. I think there are two in the rear and two up front. May only be one in rear. I will have to look. The rear one I can see on the right side has a yellow handle valve on it for quick draining a I assume. The one time I opened it. Grayish oily goop came out. It kind of looks like the valve was put on there so you could just reach under with a long stick and open and close it. Maybe this was typical Greyhound method. The fronts have the small square valves you have to use a wrench on. I haven't opened them yet. Is there any preferred method or order to bleed them? Do I just jack it up and bleed them all at once or one at a time? Thanks for the advice all. BTW I am sure I have found the culprit... As I mentioned, all last winter it was fine and it was down to 3 degrees. This year when it froze, it was only in the 20's. I used shop air over the summer and fall to air up quickly.. I just found out how wet the air was. I have an 80 gallon tank and when I opened the bottom bleeder, I about flooded my garage so much water came out. I will be getting a water separator fo the outlet before the hose and I will add one of those color changing ones for the end of hose before the tool etc. Water BAD!!!! | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 494 Registered: 7-2006 Posted From: 64.136.49.228 Rating: N/A |
it's more important than you think to keep the tanks drained.they fill with water,giving you LESS air storage AND they put water in your air system, BRAKES etc. they should be drained at the end of every day,or the end of every run,the tanks will rust out too,if water is left in them,you can get pull cords ,with a little steel cable that you pull ,so you don't have to get under there every time | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 81 Registered: 10-2006 Posted From: 4.254.130.159 Rating: N/A |
For about $8.00 each you can get pull chain operated drain valves , at the local big truck parts store. Draining should be done at LEAST once a day when running. Makes no difference on order , just drain them ALL, frequently. Use care that the pulls wont get caught on brush when in rough campsites. In commercial service these coaches were over a pit every few days , servicing the drains , looking for problems etc. FF | ||
| Cameron Jones (Crazy71)
Registered Member Username: Crazy71 Post Number: 5 Registered: 12-2006 Posted From: 75.179.158.67 Rating: N/A |
About those pull valves...do you hold them open, or do they stay open and close when pressure is down. Looks like my front driver side tank...I think that is the brake system main tank..has one on it. I haven't pulled it yet...i did open the rear one twice last night. It blew a little moisture. It left about a 10-12 inch moist spot on the pavement. | ||
| Bob greenwood (Bob_greenwood)
Registered Member Username: Bob_greenwood Post Number: 510 Registered: 7-2006 Posted From: 64.136.49.228 Rating: N/A |
pull them...they release air & water...release them & they stop....you must do this when you have your system aired-up |
