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[johnnydog]

My son has a 2008 Renault Trafic 2 2.0 DCI 115 van, which has developed a strange brake problem. These are the symptoms as he has described them.
He left work, and said he felt the brakes seemed to be binding slightly. Joined the motorway, and after approx five miles, said the brakes were binding so much that he had to drop down a couple of gears to keep moving. Came off at the next exit (approx. 5 miles from joining), and the brakes were smoking. Stopped and then tried to set off, but the brakes were binding so much that it was difficult to even pull away. He said there was smoke coming from all four wheels, but excessively from the front nearside.
When I went to the van later that day, it had cooled down, and the brakes had released, although extremely spongy, presumably due to the brake fluid having boiled, they worked ok.
An examination revealed that the there had obviously been tremendous heat at the fns wheel - the dust seals on the caliper pistons had melted, the bottom balljoint boot had melted, the front nearside pad material had parted company with the backing plate, and had left a heavy deposit of fraction pad material on the disc face. The plastic hub cap had even melted around the wheel bolts! The disc itself looked like it had been red hot as it was a red colour (not rust) around the edge.
As smoke was coming from all wheels, but excessively from the fns, I assume it isn't just a fault with one caliper sticking, especially as they released when cold.
A diagnostic check revealed the following codes - PO571 Brake Signal, P 2299 Accelerator pedal position sensor circuit, ABS 95 ECU supply voltage too low.
It obviously needs new pads; I will be changing the front flexi hoses, the bottom ball joint, fitting new seals etc to the caliper (or a good known used unit).
I wondered whether there was a fault with the master cylinder, or servo that may cause the binding brakes?
Would a 'brake signal' fault cause these issues, or is it more related to the brake lights?
He also threw in that that the brakes were binding slightly several weeks ago, but nothing like this instance, and when he came back to it two or three hours later, they had released and have been alright up until this last instance.
Any ideas or thoughts would be greatly appreciated!!

[Kevin Wood]

Only thing I can think of is that the master cylinder pushrod isn't being allowed to withdraw completely when the brakes are released. This means that it doesn't uncover the vent hole to the reservoir and given a little heat and fluid expansion, it might cause pressure in the system that will then lead to a runaway situation. That said, there might be a failure mode of the ABS system that would do the same, and you have some codes indicating that the ABS system wasn't blissfully happy with the situation.

Maybe something was causing the ABS to apply the brakes for some purpose connected with traction control or hill start assist, if fitted?

[Omegatoy]

mastercylinder!

[grifter]

My son has a 2008 Renault Trafic 2 2.0 DCI 115 van, which has developed a strange brake problem. These are the symptoms as he has described them.
He left work, and said he felt the brakes seemed to be binding slightly. Joined the motorway, and after approx five miles, said the brakes were binding so much that he had to drop down a couple of gears to keep moving. Came off at the next exit (approx. 5 miles from joining), and the brakes were smoking. Stopped and then tried to set off, but the brakes were binding so much that it was difficult to even pull away. He said there was smoke coming from all four wheels, but excessively from the front nearside.
When I went to the van later that day, it had cooled down, and the brakes had released, although extremely spongy, presumably due to the brake fluid having boiled, they worked ok.
An examination revealed that the there had obviously been tremendous heat at the fns wheel - the dust seals on the caliper pistons had melted, the bottom balljoint boot had melted, the front nearside pad material had parted company with the backing plate, and had left a heavy deposit of fraction pad material on the disc face. The plastic hub cap had even melted around the wheel bolts! The disc itself looked like it had been red hot as it was a red colour (not rust) around the edge.
As smoke was coming from all wheels, but excessively from the fns, I assume it isn't just a fault with one caliper sticking, especially as they released when cold.
A diagnostic check revealed the following codes - PO571 Brake Signal, P 2299 Accelerator pedal position sensor circuit, ABS 95 ECU supply voltage too low.
It obviously needs new pads; I will be changing the front flexi hoses, the bottom ball joint, fitting new seals etc to the caliper (or a good known used unit).
I wondered whether there was a fault with the master cylinder, or servo that may cause the binding brakes?
Would a 'brake signal' fault cause these issues, or is it more related to the brake lights?
He also threw in that that the brakes were binding slightly several weeks ago, but nothing like this instance, and when he came back to it two or three hours later, they had released and have been alright up until this last instance.
Any ideas or thoughts would be greatly appreciated!!

Try fulll fluid flush, had same thing on a citreon, kept binding then free off after use when it cooled

[tidla]

Also encountered similar fault on peugeot expert van, master cylinder was at fault as mentioned above.

Worth going for before any electrical possibilities.

[johnnydog]

Many thanks for all the replies and information!
I have now replaced the master cylinder (and servo whilst I was at it with a second hand unit whilst the master cylinder was off - just in case?), front nearside caliper with a good used one, both front flexi hoses and bottom ball joint. Drained the old brake fluid as much as possible, then refilled and bled the full system.
Nice hard pedal without the engine running; slightly spongier than I would have liked with the servo operating, but the brakes work ok, and after a short run, all seemed well. Will run it around for a bit longer before confirming that the issue has been totally solved.
But thanks again for the all the input......

[johnnydog]

Well after several days of running around, the problem seems to have been sorted. As suggested, most likely culprit was the master cylinder. Valuable info, much appreciated!