Air leak from brake exhaust

[gcyeaw]

Originally Posted by Chap

Gardner,
Do you suppose they might have run an exhaust line to the outside from the parking brake valve. Mine just dumps behind the dash, but if that is where it goes and his parking brake valve is leaking internally that might explain it.

Then when you pull out the parking brake you should get a big blast.

We really need to find the other end as impossible as that may seem. Two people, perhaps a snake camera device or something to help see what moves when you move the line, whatever.

[Robert & Dianne]

Sorry I haven't been available the last two days to help solve my problem. Today I visited the bus and tested the fan. Ran engine to 190 and fan came on. Don't think that is my problem. Can also hear fan engage when using switch on dash. Just curious with engine off and ignition on should fan come on when using switch (assuming there is over 90 lbs of air pressure)? It doesn't.
I then went to the air diagram for the 87 FC bus. (I was looking for anything that has a 1/4 inch black plastic tube connected to it.) At the top right corner of diagram there are three items that are connected to air system with a black tube #48. 2 are the air gauges the other to the left of the gauges is labeled B has a d,s inside a box and has a plunger looking device #16 at bottom. Whatever this is, it has a tube exiting that is not connected to anything. Does anyone know what this device is and where it is located?
My thoughts are that there are three tubes going through the floor from below, if two go to air gauges then this could be-just maybe-the third that is leaking!!

In addition is the air fuel treadle on this diagram? Can't seem to find.

Thank you all for sticking with this, If I didn't have a deadline of mid June for fixing the problem the search would almost be fun!!!

[Robert & Dianne]

Tomorrow I will go back to the bus and listen to air as I pull the parking brake. I don't remember hearing a loud air exhaust when applied...but then again I am old(er). Where should the valve be located for the parking brake?
As to the question of service on the brake valve. We have owned the bus since 1998 and it has never had this problem, I know we have never had work done on brake valve...I would have been the one doing it! but as I said above, I am now old(er) and may have forgotten...but in this case I'm sure.

[Robert & Dianne]

Just added a picture of air diagram questioned above to my photo album. Realized that everyone would not have this diagram and would not be able to help without it.

Thanks

Robert

[Friday1]

Robert, can you publish the legend for this diagram so we know what the numbers refer to?

Rick in Ohio

[gcyeaw]

OK, that tube you indicated in the diagram is the exhaust for the spring brake valve. It is designated with the same number as the air pressure gage hose so it is probably 1/4 inch. So this could be the hose you are seeing.

ASSUMING it is, then:

The spring brake valve is connected to coach air pressure(input) and a relay valve (output) that applies/releases pressure to/from the spring brakes.
(remember, the spring brakes are applied by removing the pressure, and released by pressurizing the spring brake chamber)


When the spring brake valve is pulled out the pressure is released from the activation port on the spring brake relay valve(s). That should result in a blast of air from the tube and a blast of air from the relay valve(s) (underneath the coach) as the spring brakes are applied. If the tube continues to leak air then there are at least two possibilities that come to mind.

1. The hand spring brake valve is leaking air from the input side. (replace the spring brake valve)

2. The relay valve is leaking air back into its input side and running up the hose to the hand valve and out the suspect tube. (Replace the relay valve) If you disconnect the output side of the hand valve you can check for air coming through that line.

You need the rest of the air system diagram to determine if there is more than one relay valve.

On my coach there is a spring brake relay valve near the front inside the frame rail blocked by the engine. I injected MMO into the system and the leak stopped. Lucky I guess as it is an all day project at a shop to change it.

[Robert & Dianne]

Hello Rick

Just added 3 pages of legend for air system to my album

Thank you

Robert

[Robert & Dianne]

Thank you Gardner
Do you know where the Spring Brake Valve is located? What you have written makes sense as my brakes do not hold completely when I give it fuel with brake set.

[Robert & Dianne]

Added full diagram of air system but don't know if it can be read without enlarging it. If you can't enlarge I will find in archives and send

[gcyeaw]

Originally Posted by Robert & Dianne

Thank you Gardner
Do you know where the Spring Brake Valve is located? What you have written makes sense as my brakes do not hold completely when I give it fuel with brake set.

I don't know where it is on your coach, mine is an 83 and the 87's are a little different. When you apply the spring brake you can have someone else keep checking where the air is coming from. That is likely the location of the valve. Of course you need to chock the wheels very well if you are crawling around underneath and are releasing the brake


The coach can move if you give it enough fuel with the spring brakes applied.

We are doing last minute prep to leave Sunday for Birds at the Beach so I may not respond much till we get settled down. But there are enough folks with good knowledge of the air brake system to keep you busy!