hi
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
thanks
john
May sound daft, but have you checked the suzis and the self sealing valves? On the Renaults air feeds down the service line when the handbrake is on. Sounds possible if it only happens with a trailer.
Is it only one trailer you are having problems with or all of them?
Release the handbrake in the lorry and pull off the yellow susie and check if it still has air in. It shouldn’t have any with handbrake off. This will tell whether truck or trailer.
Defo not the trailer it happens on different trailers. Just found out from Renault it’s the trailer release valve £798 from Renault
Had new compressor fitted not long ago. Had truck for about three years now spent hardly anything on it so can’t complain been a great truck 855000 on clock so things are going to start to go wrong I suppose.
Thanks for replies
John
Have you checked the “Trailer only brake” switch is not stuck on (Next to park brake)
Its a great tool for hill starts and split coupling as you can couple up with the trailer park brake off and all leads on whilst holding down the switch, give it a tug then let go, pull forward to close your doors in 1 go.
busy fool:
Defo not the trailer it happens on different trailers. Just found out from Renault it’s the trailer release valve £798 from Renault
Had new compressor fitted not long ago. Had truck for about three years now spent hardly anything on it so can’t complain been a great truck 855000 on clock so things are going to start to go wrong I suppose.
Thanks for replies
John
As others have rightly said check the service line coupling. As a rule if its the trailer valve it normally come up on the dash with trailer control fault but there exceptions to every rule 
Steve
hi i seem to have the problem of brakes being slow to release on trailers , where is the trailer release valve fitted on a 2007 6x2 premium