MCI MC-12 overpressure and no park brake release

[vintoolong]

New to the bus thing.
I have an 1993 MCI MC-12.
Drove it home no problems.
Started the next day and the air pressure is way too high but no park brake release, the baggage doors won't release, and no air to belt tensioners.
PLS HELP!

[chessie4905]

Could be moisture in air lines, which would be ice if 20's or colder at night.

[vintoolong]

Thanks for the reply, but I am in East Texas and its not freezing. It was 30 this morning but around 50 this afternoon when I started the bus and it acted the same. It was freezing the day after I drove it home when I first noticed the problem.

[buswarrior]

Air system maintenance is a problem.

In rough terms, the compressor is pumping, it isn't getting the signal to shut down, because the air isn't getting to where the signal line is attached, which is also where your accessories get the air.

What is the temperature?
What is the forecast?

You need to get the moisture out, but it won't come out until it melts, then you need to service the air drier so no more gets in.

Happy coaching!
Buswarrior

[vintoolong]

The signal line diagnosis sounds right.
44 right now.
30 at night on Friday high of 60 on Saturday.

[vintoolong]

it's a prison bus that sat up for 8 years!
No air system maintenance. That I know of.

[chessie4905]

Air pressure way too high. What is it going to? Higher than 125?

[buswarrior]

Where are you getting a pressure reading, and how high?

Blockage/seized valving or check valve somewhere.

Try putting air to the tank under the driver, sometimes if there's pressure put on the "other side" stuck stuff will move, not forever, but maybe once.

Remove drain valve, put in air fittings to connect remote compressor.

Happy coaching!
Buswarrior

[vintoolong]

Reading from dash air pressure gauge.
150+psi the gauge stops reporting after 150psi.

[chessie4905]

try tapping gov. on air comp. while engine running with proper blocking under coach. If that frees it up, replace it. cheap

[vintoolong]

The pressure protection valve in the passenger side front bay is leaking air like crazy and It wasn't doing that when I drove it before.
Sorry, but I didn't know the name of the component or what it was before I posted.

[buswarrior]

Relief valves will be doing their jobs, where the pressure is excessive, you can ignore that for now.

Can you safely get under and see which tanks have lots of air, and which only have a little or none?

You need to zone in on the obstruction.

Happy coaching!
Buswarrior

[vintoolong]

I will have to jack up the bus as it is all the way down right now.
Since I am new to this I have no idea where the jack points are.
I heard one of the pressure relief valves open before first posting and I immediately turned off the bus.
You are very kind to care about my problem.

[lovetofix]

I will have to jack up the bus as it is all the way down right now.
Since I am new to this I have no idea where the jack points are.
I heard one of the pressure relief valves open before first posting and I immediately turned off the bus.
You are very kind to care about my problem.

Do you have the manual for your bus?
It will have air line diagrams which will be worth your while to study and save lots of head scratching. It will also tell you where the jacking points are and mine for the MC9 even has pictures. You can get an electronic manual from BCM here:
https://www.busconversionmagazine.com/product-category/bus-manuals/mci/
Make sure to use the frame jacking points which on mine are between the rear and tag axle on the rear and in front of the front axle. Do not use the bulkheads as a jacking point.

[vintoolong]

I just got the manual two days ago.
Any recommendations for a set of jacks and blocking?