I have a premium 440 dxi on 55 plate been a fanatastic truck, but now i have a problem with the brake system.
hand brake will release the brake when solo no problem at all, but when hooked up to trailer it do not release the trailer brake ?
the only way the trailer brake releases is… release handbrake then press the footbrake down two or three times quite hard and fast.
i just changed the trailer control parking valve its the one that sits under the fith wheel but still i have the same problem, changed the apm filter too, wow there was a lot of crap in there like a carbon sludge.
I think the compressor may need replacing ? but would this cause my problem with the trailer parking brake ? any one help
When your handbrake is on signal is pushed down yellow line to trailer.Park circuit on the trailer is kept “live”(spring brakes open)
Check for blocked silencers on relay valves as trailer service brake has to have its signal exhausted through the tractor,chamber pressure exhausts through ABS module.
Is this always the same trailer or different trailers?
Bking:
When your handbrake is on signal is pushed down yellow line to trailer.Park circuit on the trailer is kept “live”(spring brakes open)
Check for blocked silencers on relay valves as trailer service brake has to have its signal exhausted through the tractor,chamber pressure exhausts through ABS module.
Is this always the same trailer or different trailers?
Could be something as simple as a worn self seal valve opening pin in the yellow coupling.
You could always remove the self seal valve and just fit the “c” male and see if that cures the problem.It might not be opening the valve just enough for a clean exhaust and holding residual pressure in the yellow line.Only takes a few PSI and the brakes will hold on.
Have a look at this thread re the drier particularly Neversweat’s post about replacing pipework between the compressor and drier. Personally if the truck is still on its original compressor and drier I would seriously consider putting new on as both will leave you stranded if either go. I tend to do this when they get to the sort of mileage where they might fail and you can also validly stick the old ones on ebay as used but working.
