Hi, I am a newbie to the world of trucking and am in need of assistance.
I have a Renault Premium 340 tractor unit (1999 vintage) and a Montracon trailer (2003 vintage) The problem i have is the trailer brakes stick (and have always stuck on) when either the foot brake or the park brake is used and are slow to apply when driving leaving the tractor to do all the work…not ideal! I have had it looked at by a local company but they have drawn a blank after replacing £1000’s of parts!! I have tried different tractors and they all suffer the same sticky problem. Any suggestions or ideas 
? Oh and I forgot to say I am based in Dubai…and must be the only white man with a truck licence here!! 
HHHHEEELLLPPPPP MMMEEEEEE 
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It sounds to me like a kink in or problem with the yellow line, as you have tried different units, maybe further into the trailer there is a kink or blockage. Maybe even the yellow connector unit to trailer is faulty.
Are you sure it’s the trailer that is the problem. i.e.Has anyone thought to put a pressure gauge on the unit’s service brake line to check the relay valve is operating as it should?
I had something similar to this with an F10 yrs ago that was about the same age as your unit is now. All would be fine for days at a time then you would apply the brakes and get no help from the trailer. There were other times when after a service brake application the trailer brakes wouldn’t release. The relay valve was found to be the culprit.
Does it have a shunt button ? I had similar problems once, and when shunt button was replaced it solved the problem.
Hi Guys…Thanks for the replies. With regard to the kink in the yellow line, when the trailer left the UK for here it passed its MOT no probs…i dont know if a line can kink on its own but i have had the floor up over the 5th wheel and i can see most of the line from the coupling up to a one way valve type thing and i cant see any kinks also i have had the palm couplings and flexi lines changed. I am reasonably confident that it is the trailer, we have had a dealer replace the foot brake valve and it made no difference - also we have tried maybe 5 or 6 different tractors and they all do the same. The pressure guage is a good ides but finding someone out here that speaks good enough english to under stand pressure is bad enough!!! Can the shunt button be bypassed or removed? I heard similar advice from the guy who converted the trailer in the UK (Hopkins motorsport)
DAFMAD:
Does it have a shunt button ? I had similar problems once, and when shunt button was replaced it solved the problem.
Trailer shunt button. 
Have you greased the S cams & slack adjusters since you started playing in the sand.
Then check your line pressures and especially that the C type or palm couplings are compatible.
As I am a honorary blone (balding you see!) i have no clue what the S cam and slack adjusters are! Sounds like i need to invest in a pressure gauge??
Has the trailer got discs or drums ? and a shunt button ?
Drums and a shunt button that i’m not sure how/if it works. I cant push the button when the airlines are connected, with them disconnected it goes in and there is a ■■■■■■ from the rear of the trailer but the brakes dont release. The button is sprung loaded so cant be left pushed in.
Well The trailer I had the problem with, had drums and a shunt button and the brakes kept sticking on as you described. In the end the shunt button gubbins were renewed and the problem was solved. I don’t know quite what was wrong with it, but it worked.
BTW, even though I used that particular trailer a lot, I never actually used the shunt button at all.
ok thanks v much…i think i’ll order some parts for tghe shunt button. 
Let us know the results.
gsf7274:
As I am a honorary blone (balding you see!) i have no clue what the S cam and slack adjusters are! Sounds like i need to invest in a pressure gauge??
I take it this trailer is a motorsport trailer and probably has not got a lot of room under it,or had a grease gun anywhere near it, so I have found you a picture. Your suggestion of buying a pressure gauge is not necessary if you dont know what you are measuring. So let us go back to basics 
Brake drums, shoes, and linings. Brake drums are located on each end of the vehicle’s axles. The wheels are bolted to the drums. The braking mechanism is inside the drum. To stop, the brake shoes and linings are pushed against the inside of the drum. This causes friction which slows the vehicle (and creates heat). The heat a drum can take without damage depends on how hard and how long the brakes are used. Too much heat can cause brake failure.
S-cam brakes. When you push the brake pedal, air is let into each brake chamber (Figure 5-2). Air pressure pushes the rod out, moving the slack adjuster, thus twisting the brake cam shaft. This turns the S-cam. The S-cam forces the brake shoes away from one another and presses them against the inside of the brake drum. When you release the brake pedal, the S-cam rotates back and a spring pulls the brake shoes away from the drum, letting the wheels roll freely again.
So you have a trailer with brakes generating heat, you have an S cam that could be seizing in the bushes because of lack of grease. The bushes may be made of polythene or nylon and can also get badly worn and require replacement.
It could also be a brake chamber with a broken, weak or twisted spring.
If it was me. I would run it over a pit and look for wear in the shafts and pump some grease into each slack adjuster,and at each end of the S cam then work the brakes a bit, you should see if they are returning.
Do not pump too much grease into the end near the wheels as the grease will get onto the brake shoes
If you look at the diagram where it says Brake Cam to the right of that there are 2 grease ■■■■■■■. Where it says Adjusting Nut that is on the slack adjuster, that will probably have a grease ■■■■■■ too.
Good Luck
Wheel nut,
Thanks sooo much for putting this much effort in for a stranger- i am really touched. Can the S cam be seen without removing the drum do you know?
gsf7274:
Wheel nut,
Thanks sooo much for putting this much effort in for a stranger- i am really touched. Can the S cam be seen without removing the drum do you know?
No the S Cam is hidden but you can probably remove the back plates. Normally the backplate will have an inspection hole to check the brake linings. I am sure if you really want to look at the S Cam, it would be easier to pull the drums off though.
To be honest I would check the S Cam shafts first, it will be cheaper than riving the whole thing to bits.
If the return springs are broken inside the drum, this will be the next thing to look at.
Im interested in what you do in Dubai. A friend of mine does a bit of rallying out there.
I work for my father in laws company GulfSport (www.gulf-sport.com) we run a 1 make series around the middle east, we are also distributors for Caterham and the road legal “F1” car the Caparo T1. We also have a shop retailing all things motorsport from helmets to brake pads - so if you friend has done any rallying in the past 3 years he will most likley know of us…small world!!
Thankyou for your guidance.
gsf7274:
I work for my father in laws company GulfSport (www.gulf-sport.com) we run a 1 make series around the middle east, we are also distributors for Caterham and the road legal “F1” car the Caparo T1. We also have a shop retailing all things motorsport from helmets to brake pads - so if you friend has done any rallying in the past 3 years he will most likley know of us…small world!!
Thankyou for your guidance.
Interesting web site. Thanks. I will mention this to them I know he was out there in 2005 / 2007 but sure they have been successful more recently too.
Problem is now fixed…it was a kink in the yellow line behind the bulkhead. I took all the info and tips you all sent me and took them to my local ‘expert’ and after 2 days of investigation stripping valves and removing bulkhead panels in 45 degrees of Dubai summer they found the pipe kinked. So sorry to those of you who wanted a “Working” holiday here!! The brakes are ■■■■■■ sharp now…as this is the only truck i have ever driven i got used to the pointless and vague brakes, now when i prod the anchors I nutt the windscreen!! (need to learn to drive again) Thanks to you all for suggestions.