Mc8 won’t air up past 60 psi

[buswarrior]

You have a very large leak, it will not be noisy, big leaks just let air out.

You need a collection of fittings in order to put an air fitting and a quarter turn valve into the drains on your air tanks.

Put air directly into tank under the driver, accessible through the door outside under the driver window, under the electric panel. And report back on what that does for you.

You could have tanks rusted out, burst/aged hoses, valve internals leaking out exhausts.

Go and turn the air supply to the shutters/dampers right off to get that ball of mess out of the picture for now.

You are going to need air schematics, better work on getting that sorted out to. No reference materials, can't help yourself.

Happy coaching!
Buswarrior

[Jim Eh.]

My suggestion would be to remove the compressor discharge line AT the compressor and connect an alternate air source. It may take a few fittings to rig up but since it is a difficult leak to find, start at the source and work your way down stream.

I have had main air lines with holes in them the size of Seattle. It is something that you would think would be immediately obvious but like said above, large holes = little sound. You may even if you have to plug the other end of the main line to find a leak.

The system normally would not leak back out the compressor discharge line when charging the "wet" tank due to a check valve on the inlet of the tank. The check valve may be missing or inoperative between the tank and the compressor line.

[SeanM]

Well finally getting her home. Found someone to tow her

[SeanM]

Will now have ample time to diagnose her sickness. I will still be asking for help lol

[richard5933]

You're way ahead of many starting out. You know the engine runs and you'll soon have it at home so you can work on it at your leisure. Good news on the tow.

[buswarrior]

Reaching 60lbs and no further suggests the leak is on the aux side. If a main line or tank was ruptured, the coach might get to 25 lbs at most.

Simulate it on your own coach by opening different tank drain valves and then run it up.

An open wet tank drain valve, used to do this to demonstrate the transit installed emergency air brake release circuit, the gauge on a dual brake system in a GM 5307 wouldn't make it past 30lbs.

With practice, you can set any tank drain valve to simulate a minor failure, to see if the trainees are actually paying attention, or just spewing forth memorised rote...

Nope, never made it into the curriculum, the rest of the trainers would have to know what all this means....

Training course can't be any smarter than the trainer...

Happy coaching!
Buswarrior

[Dave5Cs]

Change the air Governor. They are about 10.00 and lots of times thats all it is if you don't hear or see any other leaks. Check the leveling valves for leaks too.

[SeanM]

When I bought it it didn't run. Was a stuck rack. Was able to get them all free and turned over no problem. Then came the air problem lol. Always something it seems. Guess I better get used to it.

Agreed now that it's home I can take my time and go through it without feeling a time crunch. The new tank will be here this week. Will replace that then check everything you all are suggesting.

[Jim Eh.]

Reaching 60lbs and no further suggests the leak is on the aux side. If a main line or tank was ruptured, the coach might get to 25 lbs at most.

Could be but it would seem that it would be quite audible at that point. I have had mainline leaks sized so that the system will reach 60 and when the aux valves open it will build no more. This is the reason it drove us nuts trying to find the issue. But you are probably correct and in this case the problem lies in the aux side.

[Bus Lurker]

Sean,

Having the coach hauled away was a great solution.  Just out of curiosity what's the going rate to hire a Landoll?

Mike

[SeanM]

It cost me 500. Was towed 35 miles. Charged by hour. Took about 4.5 hrs due to traffic. Awesome guy to work with very fair and willing to go the extra mike. Other quotes I git where 900+ and non of them where willing to to it due to it not airing up.

ALFIE'S HEAVY TOWING & TRANSPORT

6408 Causeway Blvd, Tampa, FL 33619
(813) 917-9523

[Ed Hackenbruch]

The reason i mentioned checking the ping tank is a few years ago i helped a GM owner who could not build air pressure past 30 or maybe it was 60 lbs.  We spent several hours trying different things looking for leaks. Turned out he had never drained his ping tank and it was plugged full of what looked like reddish sand which was probably really just rust.  Used a screw driver and a piece of stiff wire to get the stuff out....fired up the bus and it built air just fine.  Even though it says right on it to drain daily, or in our case, after anytime you have driven it, most people ignore it. Don't just open the drain, stick something up there and see if anything comes out.

[Boomer]

Nice to see a trucker who isn't afraid of an over height load.