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Air brake systems and diagnostics

doublewide

Senior Member
Joined
May 31, 2015
Messages
844
Location
MA
I am so grateful to this site and it’s members for the knowledge, instruction and encouragement . Online forums are a valuable part of the future of education but can only work if there are good people, willing to share, able to communicate clearly and probably most important, site staff that continuously work behind the scene to assure that everything works smoothly.

Happy Thanksgiving and God bless.


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doublewide

Senior Member
Joined
May 31, 2015
Messages
844
Location
MA
The PP 1 and the PP 7 share supply air from the crossover between the primary and secondary air tanks. I accomplished this by adding a T to the supply side of the PP 1 ( black with orange).

The PP 1 has 2 delivery ports. The yellow loop connects one of these ports to the control port on the PP 7.5AA19633-6F62-4BA9-8BC3-9397C1C0EDE5.jpeg
Bendix PP-7 b.jpg
 
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doublewide

Senior Member
Joined
May 31, 2015
Messages
844
Location
MA
So, I have a little riddle. I think I know the answer but would like to hear what others have to say.

Prior to all of this I had noticed that one or more air leaks was draining both primary and secondary air tanks , generally overnight. After several extensive searches, the only leak that I could find was a small leak from the drain valve at the rear axle air tank. This tank is T’ed into the primary air system only. Why would this one leak drain both systems?BC618408-6F75-4C7D-B2BA-E7114F8DC98D.jpeg
 

doublewide

Senior Member
Joined
May 31, 2015
Messages
844
Location
MA
Next clue.

When I soap tested the dash valves I discovered two leaks (see post #114). In order to remove the valve assembly to repair the leaks I drained the wet tank first and was getting ready to drain the rest of the system but before I did I noticed this;
EE05A887-C211-4F45-A471-15CAC16B3699.jpeg
 
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Tenwheeler

Senior Member
Joined
Dec 15, 2016
Messages
870
Location
Georgia
So, I have a little riddle. I think I know the answer but would like to hear what others have to say.

Prior to all of this I had noticed that one or more air leaks was draining both primary and secondary air tanks , generally overnight. After several extensive searches, the only leak that I could find was a small leak from the drain valve at the rear axle air tank. This tank is T’ed into the primary air system only. Why would this one leak drain both systems?View attachment 229428
You are doing an awesome job there! Things with these systems get confusing. Ford also did some things different than the rest of the pack. If you are trying to combine the different set ups could be causing you issues.
Regardless of the system a check valve should be present that prevents primary or secondary air from leaking to another tank.
 
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