STW mechanics/technicians for van brakes help?!

  • This topic has 16 replies, 10 voices, and was last updated 3 months ago by  murf.
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  • STW mechanics/technicians for van brakes help?!
  • souster4
    Member

    ** warning this is long winded **

    Guys I’ve had this 2012 Renault trafic sport for 2 years now. When I picked it up the brakes were crap, it had been standing for some time and very low mileage (20k). (I know it’s an old van but I really like it)

    The symptoms were low mushy brake pedal, with poor braking. But passing MOT no issues. Anyway, the brake discs were in a bit of a state from not enough use, so I changed all four with new pagid brake pads. Wound the pistons back in the rear, with handbrake off and then pumped the foot pedal.

    After bedding them in it was still no improvement, so I bled and bled the system in several ways, no luck! Then fitted a new OEM master cylinder, again you guessed it, no luck. Also changed pads a 2nd time.

    Shortly after, I had a Renault mechanic apparently do a ABS module activation bleed, which didn’t help at all. Followed by another mechanic shortly after having a look over it. Both could find no issues.

    Anyway, my dad has a 2006 Renault trafic and the brakes on that are fantastic, just as you’d expect, similar to a car. Which has also had the same discs and pads fitted by myself. This said vehicle failed MOT in the week on handbrake cable. All passed now.
    While working on that vehicle (h/brake cable)it has drawn my attention back to my brakes again. And while messing with the handbrake lever on dads 2006, I noticed I couldn’t feel movement under the foot pedal. Where as on mine you can!

    So since carrying out the work on dads, I’ve lifted my handbrake slightly while driving,and used the foot brake. And WOW!!! Cant believe how sharp the brakes feel, and the pedal travel is far reduced and feels how it should. Although it does have a tendency to skid on the back.
    Any ideas why its braking better???

    I did some tinkering lastnight. And clamped each flexi hose one at a time, made no difference to pedal regardless of which one. Servo holding pressure for days, same as the other van. Also pedal sinks on start up, same as other van.
    But the pedal travel on mine is twice that of dads, before the van is even started.

    Any thoughts guys?! I’m guessing it will be a miracle if I get a response, let alone a solution hahaaa

    andyl
    Member

    Are you sure the rear shoes are adjusting properly?

    Sounds like the shoe has too far to travel when on the foot brake so when you lift the hand brake it is pushing out the rear shoe a bit giving the hydraulics less to move.

    souster4
    Member

    Thanks Andy.
    Its discs on the back, theres a parking brake actuating lever on each caliper, both sides are returning to the stops (handbrake off) and also are actuating (handbrake on).
    Whether or not the caliper insides are working correctly I dont know.

    Strange this is, when the handbrake is applied with dads when driving, it doesn’t really make any difference at all to the feel of the pedal.

    andyl
    Member

    so it’s a combined hydraulic/cable caliper for the rear? Much prefer a drum for both or a combined drum disc.

    The brake should still auto adjust so that the pad only has to move a tiny amount. When you say it’s returning to the stops it sounds like they are fully retracting and leaving a big gap.

    souster4
    Member

    Yes that’s it mate. Combined cable and hydraulic caliper.

    I wound back both rear pistons again tonight without the handbrake on, reinstalled the pads etc and pumped the brake sooo much, and took it for a mile drive before applying the handbrake. Still made sod all difference.

    I dont think they are fully retracting like all the way into the bores, because the piston was out a decent way on both sides before I wound it back,and both handbrake and foot brake for the rear passed its MOT a few weeks back.

    I just thought I maybe closer than ever with finding the solution after applying the handbrake while driving. As I say, feel quite sharp and good high firm pedal. Bit of a tendency to skid on the back though.

    Clamp all the wheels. Test pedal. If no improvement it’s not the wheel parts.

    Try pumping the pedal. If there is some I imorovement try pressing an dholding pedal, if it sinks again, that might mean an internal leak in the master. Get blanking plugs for the brake line ports, block them off. Test pedal. If the pedal is mushy or sinks, it’s the master. If not the problem is probably in the abs modulator may be bad.
    Remove the wheel blocks one at a time testing each. If you find a problem in one, block it off again and test the rest anyway, in case more than one has a problem.
    Could be a bad hub bearing allowing rotor to move. Calipers installed on the wrong side so the bleed screws are on the bottom. Stuck slider pin. Incorrect bleeding (pedal pushed to floor, e.g).
    Seals in the calipers my not leak fluid when pedal is pressed but might suck air in past seals on retraction. In essence meaning the system needs bleeding all the time.
    Did you bleed the master separately when you installed it?
    Seems unlikely to be the master since you replaced it but there might be air in it still, air can be bloody sneaky in brake systems.

    The handbrake pushes the pistons out a bit so seems to solve the problem because they aren’t moving far enough on their own, like your dad’s do. The fact that they are looking might indicate an absolute system problem or it might mean the handbrake pushes them out far enough so the abs can’t retract them enough.

    souster4
    Member

    Thanks cromolyoly!!

    Some time back i clamped all four flexi pipes, it did stiffen the pedal, but only due to there being nowhere for the fluid to go. Removing one at a time left the same results regardless of the one it was.

    The pedal doesn’t improve at all when pumped, engine on or off it doesn’t seem to make a difference. And when the master cylinder was changed, that didn’t make an ounce of difference either. I’m certain theres no air trapped!

    Calipers have all bleed nipples at the top, sliders greased and perfect to be honest. Hub bearings are new on the back, had 3 different disc pairs on and no improvement. On the front I’m not sure, but pumping the pedal while stationary would notice that.

    One thing I do want to say is, I had a fairly old land rover some years back, and you could adjust the push rod on the brake servo, this altered the pedal height, and also had an effect on the front or rear brakes. Because it would allow a full slug of fluid to be exerted in the master cylinder. Wondering about that?

    Cheers all

    Premier Icon slackalice
    Subscriber

    I would imagine there is a rear brake compensator fitted that would allow more fluid to go to the rear brakes when the suspension is loaded, ie carrying stuff.

    You mentioned that with a slight tweak of the handbrake the brake pedal felt good but the rear wheels locked up easily, which whilst the handbrake tweaking is a bit of a red herring, it might be that the compensator is stuck open, or the mechanical linkage that operates the internal valve is seized or not connected to the torsion bar/swing arm or wherever its meant to be connected to.

    Seems like you’ve checked everything else, so by process of elimination, that would be the next logical step.

    Otherwise, perhaps change the servo? It may have an internal leak or the hose has a small hole? Again you mentioned that the servo is holding pressure, how did you ascertain that? Without the engine running, the servo does nothing to help.

    Premier Icon Davesport
    Subscriber

    Long shot but worth checking. I had a similar problem with my old Volvo estate after it was in getting new wheel bearings. It was my wife’s shopping trolley and I never really drove the thing. She complained about the brakes after the WB’s were done & I had to agree, they’d gone from sharp to slower-downers. The garage insisted there was nothing wrong but a quick look by me revealed both front calipers sitting slightly on the piss. What they’d done was bent both of the front uprights in the hydraulic press by a couple of mm and it was enough to make the brakes loose a lot of power and made the pedal a wee bit soft.

    It might be worth check that all the caliper mounting faces are parallel with the discs.

    hols2
    Member

    I would try stripping the calipers, cleaning the pistons, lubing with rubber grease, reassembling and bleeding again. If it has single piston calipers (i.e. the caliper slides instead of having two pistons) make sure that it’s sliding freely. If the calipers are seizing, you’ll get crap braking and long pedal travel.

    Premier Icon PePPeR
    Subscriber

    Not read the other replies, but I’ve found when fitting rear brake pads on cars with handbrake on the main disc, I only wind the brake slave cylinder back just enough to get the pads in. It sometimes takes a little fiddling to get them just right, but it makes a massive difference. I also undo all the cable adjusters so there is slack at the caliper so it doesn’t interfere with the lever movement.

    I’ve just done the handbrake on my van, someone had wound up the cable adjusters so tight the drum brake levers in the hubs were hitting the centre of the hub before putting the brakes fully on.

    Well, it’s got me beat.

    Since it sat for a while before you got it, I’d be thinking debris in the system. Maybe water in old fluid that boils off in use?
    If,for instance, you bleed a an old system without a block of wood under the brake pedal, it can sometimes move the master cylinder piston to a dirty/corroded part of the bore, where it doesn’t usually go. This can tear the seals and dislodge debris into the rest of the system, including the abs modulator. Similarly, if you push the Pistons in to change pads, some people recommend opening the bleed valve first so any crap is expelled, rather than pushed back into the system.

    Did you bench bleed the new master? If not that can be done in place but you’ll have to get the back end up in the air/on a good slope. That’s kind of grasping at straws though

    If you clamped all the pipes near the wheels and the pedal felt good it must be a problem at the calipers. Which leaves only two real possibilities. The pistons are retracting too far, or are not extending far enough. Which is usually seals/air, or the water in the fluid.
    I’d probably repeat that test with the new master, make sure nothing has happened in changing that.
    Then start looking at any problems with bulging hoses/pipes, connections moving.

    Flush brake system in case it is debris/water.
    After that probably replacing calipers. It’s possible, if it sat that the Pistons have developed a lip due to ruat which has damaged the seals or is preventing the square ring from retracting the piaton properly. Also pins may have developed flat spots so even if grease d well may not move properly.
    At this point it may come down to gradually replacing all the parts til you fix it. There’s no way to see problems in calipers/fluid

    You could try the time honoured reverse at some speed and jam on brakes trick a few times. I can see that might work with e.g.old drums that self adjusted in reverse but some people swear by it for all brake systems.

    Sorry can’t be more help!

    mc
    Member

    With the pistons wound back, and the calipers bolted on, do they slide freely?

    I know you’ve said they’re all sliding, but I’ve seen more than a few where something has been bent, causing them to bind once tightened up, resulting in a soft pedal or brake bind. However on a handbrake caliper, it’s far more likely to cause binding rather than a spongy pedal. However any flexing would be noticeable if you watch the caliper while somebody presses the brake.

    However, given the vehicle, it’s very likely just needing a couple calipers. They’re not exactly the most reliable of brake calipers.

    trail_rat
    Member

    The pedal doesn’t improve at all when pumped, engine on or off it doesn’t seem to make a difference

    Can you elaborate on this.

    There should be a marked difference between engine on and off…..if there wasn’t it wouldn’t pass mot.

    Erm….it’s fine, my mk7 Transit has similar hydraulic/cable ratchet handbrake cylinders and it has the same symptoms as you describe. Mushy long travel pedal, better with handbrake on a bit. I came from a Landrover and googled my van’s brakes when I first got it thinking they weren’t right – plenty of other people asking the same but they are in fact okay. Has passed 5 or 6 MOT since and been on its nose emergency braking a few times.
    The whole system has been bled a few times over the years due to replacing corroded brake lines, has also just had two new rear calipers fitted due to pitted pistons. Still feels exactly the same. If it’s passing it’s MOT and it brakes in a straight line in time to not run over baby robins then it’s fine.

    souster4
    Member

    Guys thanks alot for the replies. Sorry I’m late getting back to posting, was away over Easter with no wifi.

    The brake pedal is harder with the engine off and the vacuum exhausted after several presses. Then softens up when engine started and vacuum pump engaged. Both with the engine off and on, the pedal travel is twice that of what the other van is.

    100% sure theres no debris in the brake lines and calipers, it hadn’t done many miles when I picked it up either.

    I’ll be honest, I haven’t checked for binding or misalignment anywhere, that’s something I need to investigate.

    Thankyou for your time in posting

    murf
    Member

    I have a 2008 Trafic van, the 9 seat version with Windows all round.

    I feel the brakes in mine are a bit spongy and that there is a fair amount of pedal travel too. My mate drove it and also thought the same.

    I’ve had the rear calipers off, changed pads and bled the system but it still feels the same.

    Could it be that your dad’s van has a different abs unit or Master cylinder etc and that the brakes just have better feel?

    Mine stops fine when you stamp the pedal, the pedal just doesn’t feel that great.

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