Rear Brakes Failing Mot

[davemar 16]

One of the things my 205 GTi (1.9 Mi16) just failed on was the rear brakes. They actually failed on several points, the discs were pitted (easy enough to replace), the braking force of the O/S was weak, and the handbrake was weak on the N/S.

 

I don't think the calipers are seized so that the brakes are jammed on, I would have noticed that. I did fiddle around with the handbrake cables quite recently as I felt they were too long (the outer rather than cable itself) so where always coming detached from the bottom of the car. They were better than they were before, but still not great.

 

The weak brake (via pedal rather than handbrake) is more of a worry, is it possible the compensator is causing trouble? How can I check whether it is?

[welshpug 1,626]

Firstly you need to check how badly they failed (should have a printout IIRC) and how badly pitted the discs are, if its an uneven area then for definite replace them.

 

I highly recommend sourcing original equipment pads along with branded discs (I had similar problems for my MOT 6 weeks ago )

I replaced mine with standard Brembo replacement discs and Textar pads (Textar are a well known O.E manufacturer used by PSA) bought from my local GSF.

 

It is quite possible that the compensator's may be seized and restricting the flow, to check this pop a tube on a bleed nipple (as if you were bleeding the brake) open the bleed nipple and see how easily the fluid comes out.

 

Checking whether the caliper is seized on the rear isn't as simple as the front due to the self adjusting mechanism, but it wouldn't hurt to strip the pads out and wind the pistons back, clean all the dust+corrosion off then re-assemble with a little copper grease.

 

On re-assembly leave the handbrake cable disconnected from the lever, pump the pedal until the pads clamp the disc, then re-attach the inner cable, leaving a gap of 5mm between the inner and the lever on both sides (this ensures that the lever returns to the off position when released and the self adjusting mechanism works)

 

If you find that the handbrake effort isn't as good as it should be, the cables could be past their best, not a biggie at about £12 a pair, make sure you get left and right as they are handed (one is an inch or two longer than the other)

 

Have a play

[Emmy Seize 8]

Firstly you need to check how badly they failed (should have a printout IIRC)

 

Exactly! have a look at the printout.

 

It is very likely that one of the compensators is giving you trouble, but not as you might think.

 

My guess is, that one compensator is shot, thus NOT restricting brakepressure as much as it should be.

 

I had this on three different cars last year and only from the readings on the MOT- (or TÜV, over here) printout it became evident what actually went wrong.

 

I now have a very nice collection of compensators stuck "open".

[davemar 16]

Exactly! have a look at the printout.

 

It is very likely that one of the compensators is giving you trouble, but not as you might think.

 

My guess is, that one compensator is shot, thus NOT restricting brakepressure as much as it should be.

 

I had this on three different cars last year and only from the readings on the MOT- (or TÜV, over here) printout it became evident what actually went wrong.

 

I now have a very nice collection of compensators stuck "open".

All I've got is one of the brakes is at 13% of what it should be. Knowing what it should be is the key. I do vaguely remember a few years ago replacing the compensator on the side that wasn't giving the weak results, assuming the compensator had gone open. The car passed after doing that, so that might be the trouble again.

 

The car has been sitting around for a few months too, which doesn't help the brakes.

[davemar 16]

I removed the pads, discs and calipers tonight to check them over. The left-hand caliper wound back easy enough, but the handbrake lever was stiffer than I would expect, and it wouldn't spring back into position when let go, it would really slowly creep back. The right-hand caliper didn't wind back so easily, and the rubber seal had a hole in it. The handbrake lever moved more freely and did spring back when let go.

 

I suspect I'll have to replace both calipers. I did have a go at dismantling the left-hand one with the stick handbrake, by removing the handbrake mechanism. The grease inside it was very claggy and dry. I removed the bits, and cleaned it up, but it appear virtually impossible to reassemble due to the piston not moving in.

 

I had a go at bleeding the left hand caliper and it appears to be freely flowing fluid when the pedal was pressed, but it's hard to tell when you're on your own with that one!

Didn't check the other caliper though.

 

Does anyone know the cheapest place to get a pair of calipers quickly? (I'm in Sussex).

[Emmy Seize 8]

Well, I could send you a pair. But that will probably take too long.

 

Bear in mind that 206 and Renault Clio ones fit as well, that broadens the choice a bit.

[davemar 16]

I replaced the calipers, disks and pads and put it through the retest...and it failed again. The rear left was fine (scored 100-120ish) but the rear right was weak (scored 40ish). So could it be the right compensator is a bit clogged? Is it possible that I hadn't bled the brakes well (quite possible!) and air in the system has made this one weak?

 

If I need to get a new compensator does anyone know how much they are from a Pug dealer? I know they are around £35 from GSF.

[jord294 87]

All I've got is one of the brakes is at 13% of what it should be. Knowing what it should be is the key. I do vaguely remember a few years ago replacing the compensator on the side that wasn't giving the weak results, assuming the compensator had gone open. The car passed after doing that, so that might be the trouble again.

 

i'd go with what you say above.

 

i had exactly same problems with my car at test. it only just passed. but for peace of mind, i will be putting a new compensator on opposite side aswell

[Emmy Seize 8]

So I was right, then.

 

The left compensator is shot.

 

110 to 120 is far to much, indicating the compensator is stuck open.

 

40 on the other hand is a bit low, so it would be clever to replace both compensators.

[Guest Nath]

ive got a similar problem.

 

failed MoT on rear brake balance.

 

OS is reading 50 and NS 120, now we have been concentrating on the OS with poor performance but could it be the other side?

 

and where are the compensators supposed to be located on 1.9s?

[davemar 16]

The compensators are in the brake pipes under the car roughly 6in-12in in front of the rear wheels. They are just hexagonal cylinders about 4in long with the pipes going in at each end. Not difficult to get to, just one of those brake-fluid-everywhere-rolling-around-under-the-car sort of messy little jobs.

 

I'm going to pick up a compensator from the dealer (it was about £42+VAT) in the morning, and might replace it on the stronger braking side. I'll then bleed both sides thoroughly, as I'm sure the pedal feels a bit softer than it ought to.

 

Emmy, what sort of braking reading should I be getting on the rears?

[Emmy Seize 8]

Emmy, what sort of braking reading should I be getting on the rears?

 

 

50 to 80 is a good guess.

 

However, readings depend very much on the testing bay.

 

I went through several printouts of various cars and there were big differences between them.

 

Funniest was a standard 1.9 setup with alledgedly 280 up front and 150 at the rear.

 

Best thing you could do is watch the ratio between front and rear.

 

If the rear has less than 50% of the front, then the rear brakes shouldn´t lock up early (which is what the compensators are for).

[Guest Nath]

50 to 80 is a good guess.

 

If the rear has less than 50% of the front, then the rear brakes shouldn´t lock up early (which is what the compensators are for).

 

 

so i may have a compensator with too much flow on the NS..

been looking into the OS as not having enough force and can't find a thing wrong.

 

i had 50 OS and 120 NS...

 

also the MoT failure was for little or no effort recorded on the OS rear..confused

Edited February 29, 2008 by Nath

[Emmy Seize 8]

also the MoT failure was for little or no effort recorded on the OS rear..confused

 

Mot engineers don´t seem to be prepared to test cars with static compensators like the GTI´s nowadays.

 

Modern vehicles allways show full figures at the rear axle as dynamic wheight transfer is just not happening while being stationary, thus not activating the compensators at all.

 

Most of the testers obviously expect very high readings.

 

Our Volvo V70 managed more than 300 at the rear as I had a spare set of wheels in the boot keeping the back end down on the rollers.

[davemar 16]

I'm currently replacing the compensator on the side with the higher reading. I'm having a nightmare though, as I had to cut the pipe as the union wouldn't undo and refit a new union. Unfortunately I can't get the new union to seal properly in the compensator, so it spuzzes out fluid when I try to refill/bleed the system. I used a Draper pipe ender thingy to make the end of the pipe splayed; but the compensator really needs a mushroom shaped end to the pipe, rather than a funnel end. Any suggestions to ways around this?

 

I got totally hacked off with all the brake fluid everywhere, it just seems to get onto everything; I must have used a whole kitchen roll mopping stuff up and loads of latex gloves.

[davemar 16]

Well, she got through the MOT! The rear brakes now measured the same force, so I was right about the compensator on the left side being open. Mind you, they only just scraped through, and the handbrake was borderline too.

[Guest southcaver]

Same thing here, failed my mot on os and ns service and parking so striped them down and the pads were shot.

Replaced them today and the drivers side was fine but the other did nothing when the peddle was pushed(fine with the handbrake) undid the bleed nipple and there was nothing so i assumed there was a kink in the pipe or something because ifluid was coming out at the master cylinder when i slackend it.

I traced it back to what i now know is the compensator and its not letting anything through.

so I take it it needs replacing then?

what would happen if i just joined the pipe with a normal connector?

only thing is its booked in for the retest at 4.30pm tomorow!