Rear Brakes Not Working

[Guest simonh9]

Hi All,

 

I'm very new to 205 ownership and just trying to get it through it's MoT (bought without - been sat for 2 1/2 years).

 

It failed on rear brake efficiency and pitted discs. The tester said the efficiency was bad due to the discs. However, the handbrake wasn't mentioned and it (the handbrake) didn't seem too bad on the way home from the MoT (certainly better than my 306). I've fitted new rr discs and pads tonight, but when you spin the wheel and push the brake, you have to press reasonably far and while it stops the wheel in the air it doesn't lock the wheel with a bang (if you know what I mean - perhaps 'dung' describes the noise I'd expect better ). When driving the car back, the pedal didn't feel particularly spongy (not particularly firm either, but it doesn't pump up like there's air in the system). The car had previously passed an MoT before being laid up straight away due to engine problems.

 

It was getting dark so I couldn't check out much more this evening. My only thoughts are that it could be the compensator, but I understand there's two on the 1.9, so for both to stick/block would be quite unlucky/likely. Also one side wasn't singled out on the failure sheet (simply rear brakes), which makes me assume it's both sides.

 

I will try bleeding them tomorrow to see if I can get any fluid out, but does anyone have any bright ideas in the meantime (I'd like to 'hit it' this weekend and get the free re-test on Tuesday, which means being ready to get whichever parts I need). If it is the compensator, is the 1.9 part shared with any other PSA cars, which are more likely to be at the scrappy?) [Edited to add I've just seen they're shared with zx/306]

 

Many thanks in advance,

 

Simon Hill

'89 Alpine White 1.9

Edited March 26, 2009 by simonh9

[one-lady-owner 1]

If it's been sat for that long unused then a complete bleed through and renewal of the brake fluid is probably a good idea anyway!! Definitely worth a shot at least! Good to hear of another GTi getting back on the road though!

[CosKev 16]

A few people remove the compensators alltogether,and reckon it makes no diffrence to rear brakes locking up/over braking etc

 

As you have said,try bleeding first and see how you get on with fresh fluid in there.

 

One thing I did notice when I did mine on 309 the fluid takes ALOT of pumping to get threw to the rear calipers.

[MrG 3]

maybe give everything a damn good clean with some brake cleaner including those sliding pins at the back, Mine were all gummed up but responded well to this.

[pug_ham 241 3 Cars]

Personally I'd expect that the rear compensators have seized & aren't flowing any fluid so the brakes don't work.

 

Obviously because the handbrake is working the calipers aren't seized.

 

Unless you can test them or are buying them from a known good source, second hand ones are a risk because they might not be any better than the ones you remove.

 

Graham.

[Anthony 1,000]

Did you get given the sheet with the brake test results on? If so, what does it say?

 

A few people remove the compensators alltogether,and reckon it makes no diffrence to rear brakes locking up/over braking etc

If you're running GTi-6 brakes on the front then yes, that's true, but don't remove the compensators if you're still using standard calipers as they can and do lockup.

[Guest simonh9]

Many thanks for the advice.

 

With a bit more time this afternoon, I've had the brakes off again and double checked everything's free. Then jacked up both sides, jammed the brake pedal on and tried turning the wheel (which does with a bit of effort). Have bled the calipers (no air came out) and given both regulators a few sharp taps, which made no difference. I thought I'd try my 306 Rallye to see what that did and sure enough, it did exactly the same (and yes, I jacked the suspension to take account of the load compensator), which is all the stranger. I didn't do the turning by hand check with the old brakes for reference, so I've no idea if it's an improvement with the new brakes or not.

 

Maybe it's just my expectation that the wheel should lock solid, or perhaps I have superhuman strength and don't know it (unlikely). The fluid flows OK (during bleeding and also without pads in, the piston easily pushes out), just not much pressure I guess.

 

How does this particular compensator/regulator work? On other cars, it's a spring with a chamber, which moves up as the pressure increases (increasing the volume and hence limiting the pressure rise rate). On the 205 part it looks quite compact so I don't know if it works in the same way. If it did and was seized, more fluid would be drawn through. from the master cylinder to fill the void (if there was one) and the problem would be unrestricted pressure, not over-restricted pressure. Don't suppose anyone has a cut away diagram do they

 

Is it a common part to fail (just as it would indicate both have failed if that's the cause)

 

Oh and I didn't get the brake test result sheet. According to its last MoT, it also failed on rear brakes, but this was simply a case of cleaning up and freeing off the calipers (according to the service history) and it subsequently passed.

 

Thanks again,

 

Simon

[Tom Fenton 1,526]

O/T, did you go to Loughborough University?

[Guest simonh9]

O/T, did you go to Loughborough University?

 

I thought that was you Tom! Yes, How's it going? Still working for British Steel?

[Tom Fenton 1,526]

Ha ha, thought there couldn't be that many Simon Hills in Bedford! I am at the moment yes, for how long though is another question with the UK as it is.......

 

The 1900 compensators are basically a check valve that closes over a certain pressure. When they fail what usually happens is that you get more braking effort rather than less as they fail to close. Make sure the calipers are free to move both the pistons and also the sliders. Also make sure the pad nearest the piston can slide in the guides. When changing discs and pads the handbrake can be poor for a bit until they bed in properly, if everything else seems in order I'd be tempted to take it the "long way" to its MOT and give the brakes some hard use on the way and then see how you go.

[Guest simonh9]

Cheers, Tom,

 

The sliders seem fairly free (certainly enough to move by hand). I'll maybe just give them a thorough dousing in WD40 and then clean up the guides and then stick it back in for MoT and see what happens.

 

Then it'll be on with the rest of the jobs!

 

You seen Jon, Johnny, Marc etc recently?

[Tom Fenton 1,526]

Yeah we're still in touch, Mark is now married with 2 kids, and here is the shocker, Giles has a fiancee and a baby daughter! Jon has got himself a Honda NSX and Jonny is in the final stages of rebuilding his 944.........

[Guest simonh9]

Thanks everyone for the advice. The car passed the MoT today after bedding the brakes as best I can on the way there. It still seems very odd that you can turn the wheel by hand (even allowing for it not being bedded in), but I didn't like to ask any questions so took the certificate and ran!

 

Nice to have the car on the road now though, although this has just highlighted all the other jobs that need doing and made me realise how much I've already spent!!

 

Cheers,

 

Simon

Edited March 31, 2009 by simonh9