Brake problem

u have problems with tank protection valve.

Tank #3 (trailer brake tank) valve goes bad. from this tank trailer control valve and trailer red line are supplied.

normally valve opens at ~80 PSI

 

ouh, check protection valves manyfold

 

on EU volvos it is on right frame rail, on US versions - usually on left frame rail, it is made of plastic, with quick connections

http://www.ebay.com/itm/Volvo-Tract...k-Conn-Fittings-for-VN-24426099-/111164954864

check also park brake knob valve too

 

btw, when this valve goes bad, red knob pops out, becouse really there is the spring inside and this spring pushes knob out so it is held with air pressure of park brake air tank.

it is not all. on some cummins engines air servos are used, and it may leak too. No air in system like u got, so check cummins turbo air servo piston for leak too

 

really wierd. u have to check lines from valve to tanks.

What valve did u change? in cab ore air processing valve?

 

trailer control valve test.
1)remove air pipe from port nr 43 on the trailer control valve.
2)release hand/park brake air should be coming out of the pipe you removed from port 43.
if not check pipes on port 41 and 42 if air comes out of either one of them put the pipe blowing air into port 43

for treddle / foot brake
1)remove pipes from port 41 and 42
2)tramp brake and air should come out of one or both these pipes.


remember #3 air tank should be the same tank supplying the hand brake and the trailer control valve with constant air.