MCI8 air issues

GI-Jane · September 03, 2017, 07:40:36 AM

Good morning, all. Thank you for the help. I cut my Labor Day weekend short to work on this bus. Today's schedule is jack/block/wheel removal/explore.

Oonrahnjay: Yes, I have the MC8 big maintenance manual and big parts manual. Lots of photos. The printing is difficult to read on some diagrams, but they are in pristine condition.

Brmax: The air gauge not lifts off pegged zero. I have the spare out and have starting following the accelerator linkage for problems.

This is another Murphy's Law scenario; The bus is parked in a large RV storage area. I was informed 2 weeks ago that they are losing one area for street development. Lucky me, that's were I am parked. I don't need to move far, but ASAP. I must move down a couple rows, a few zig-zags, and into a new spot. But having accelerator and brake release are somewhat important, even for a short move.

This problem started acutely. Typically when I start the bus just to warm everything up, she airs up really fast. On this particular start, zero air pressure and zero accelerator. And loud air leak sound up by the 2 front tanks. I am still hoping for simple repair, even if just temporary for the move within the yard. Update by tomorrow pm. And I will study the protocol for getting photos into my posts. Thanks again. Kirt

brmax · September 03, 2017, 08:35:47 AM

If theres a harbor freight close, i would pick up a "shorty/low profile" 20ton hyd. Jack these work well when these coach's have no air. In my 2cent op
Im not familar with the 8 throttle, although looking under and behind the front wheel you might see the tanks. If so maybe able to see the pull type drain valve on each. One of These maybe stuck open. I keep a broom stick, cut off and a super high tech drywall screw at the end, on the side. This works simply for a momentary pull the valve off center, draining tank of any moisture. On a another just taping on the end and watching the air flow against the tape ribbon could give a clue as to the specfic leak. Take a look at the dryer in that area for leaks.

Good luck today on your mission

Floyd

gumpy · September 03, 2017, 03:54:37 PM

It it were me, I'd start at the engine side for throttle issue.

Brassman · September 03, 2017, 06:14:43 PM

If it were spring brakes I caged the brakes and move it with a small tractor.

bevans6 · September 04, 2017, 04:32:49 AM

No cage bolts on this bus, of course, but it is completely possible to pull the rear wheels, undo the bolts that hold the brake cannisters to their mounts and back off the rear brakes for a short tow. There is room to actually fully remove the DD3's with the pushrods fully extended, I've done it. Emergency fallback, perhaps?

Brian

GI-Jane · September 04, 2017, 05:21:06 PM

Bus is relocated. Yippee.
-Jack/block/jack/reblock - remove passenger wheel.
-Air supplied to drain line. Slid under to inspect 2 front reservoirs. (Which, even with the Railroad Tie blocks and the hydraulic jack as an emergency backup, was a little unnerving. But I got used to it.)
-Air leak originated at the wet tank draincock. It was in two pieces. I scrounged through my air fittings box and found a plug the right size as a temporary fix.
-Resupplied air from the drain line. Bus aired right up to 120 lbs. It took a couple hours to leak down. During that time I topped off all the tires.
-Decided to attempt to move bus. It was a short move and completely flat. Even if I had no accelerator, I might get her to roll. No sooner than I nudged her into 1st gear, 2 problems miraculously resolved. a) I had throttle and b) the generator started contributing air pressure. Drove to new parking spot and pulled the batteries. I sure wish I was driving this bus. I think she needs the exercise.
Thanks again for the support and advice. Kirt

GI-Jane · September 04, 2017, 05:26:10 PM

Do you ever get a song stuck in your head? Or maybe just part of a song? I kept hearing Johnny Horton as the temp approached 100 degrees, today. I wonder what hiway I would take to go north?

GI-Jane · September 04, 2017, 06:21:57 PM

Now I am shopping for this valve. According to the MC8 maintenance manual, 4-26, this is the drain cock on the bottom of the wet reservoir tank. Jumping to the MC8 parts manual, do I need 4B-19-4, Ejector Valve Assembly? Searching for that part on Vintage Parts, it shows that valve to cost $1,025. I am hoping this is not the best approach to replacing this valve.

gumpy · September 04, 2017, 07:55:22 PM

Well, kudos to you. You found the problem, and you found an acceptable temporary solution.

So, are you talking about the wire pull valve on the side of the tank? Call Luke or C&J Bus Repair (cjbusrepair.com). Or, just go to the truck parts store and buy new ones there. Probably about $12 each, with the cable, though it's been awhile since I replaced mine and a lot of brain cells have died since then.

Possibly MCI part number 12C-7-29.

bevans6 · September 05, 2017, 04:07:40 AM

I got mine for around $8 each at a truck parts store. Extremely standard part, I think 3/8" NPT thread. Good job well done, btw.

GI-Jane · September 05, 2017, 07:13:31 AM

Yes, it had a plastic coated cable attached to it with a split ring. Looks like it was set up so a driver could easily test it, or drain tank, with the cable, without crawling under. Thanks. That's a much better option than the one I found. Kirt

gumpy · September 05, 2017, 07:29:13 AM

I think the one you found was the automatic drain system.

The cables are long enough to come out into the wheel well. I attached them to my inner wheel well with a stainless cable clamp so I can reach in and pull them. The one on the aux tank is in the compartment, so not so convenient. You're supposed to drain them daily. I'd recommend you replace all of them.