SafeChav

Got a Mk3 cabriolet, with a S2 lump in, and after quite a few situations of touching cloth ive decided to upgrade the brakes

sounded like a good idea, but i'm getting to my wits end now. The upgrade consists of a complete 2wd cossie set up, 4 pots on the front, and disc conversion on the rear. all fitted, all piped up, and connected to a 90spec 23mm master cylinder, all should of been well.

started the manual bleeding method, 25 minutes of pushing the pedal on the FIRST caliper and only an inch of fluid in the jar, i opted for an easy bleed kit, half an hour later they're all bled, used a litre of fluid, engine on, push the pedal, pedal hits the floor Driven it very briefly, and brakes do begin to come on at the bottom of the travel. feels like air....but ive bled them!

definately no leaks or anything as the pressure bleeder would have made them evident.

decided it must be the master cylinder, changed it, wasted another litre of fluid getting the exact same result.

a mate pointed out apparently its a common problem with rear disc conversions on RST's, and suggested dropping the calipers off to bleed them as they are too high. sounds feasable, just wondering if anyone else has had similar problems, or has got any sensible ideas?

Much appreciated if u can help, golden star to the best suggestion lol

DazC

iTrader: (1)

Are the bleed nipples at the highest point of the calipers?

The servo push rod has a small nut in the centre of it whci you can adjust outwards which will reducr the pedal travel. Don't over do it though otherwise you will hold the brakes on slightly and cook your brake discs and then they will be warped.

matts1

Remember that with bigger calipures and rears fitted aswell the Master cylinder may have to narrower core. May need a S2 or Mk V master cylinder.

Had a similar problem with my s1, but not as pad, just to much travel in the predal before it started to brake, was told a master cylinder with a bigger core was needed.

SafeChav

Firstly, the bleed nipples on the front callipers point directly up 12 o'clock position, not with the rears however as this was totally impossible due to how far the handbrake cable will stretch and the limitation of the brackets only allow 2 different mounting positions. The calipers as you look at the wheel are between the 10/11 o'clock position, meaning the bleed nipples point out towards the rear of the car at a 3 o'clock position.

The nut on the master cylinder makes sense, but im sure however that it feels like air as the pedal has no hardness in it at all, but wouldn't go a miss, i've got nothing to lose by trying it Is that however what the nut is intended for, or a bit of cheat if you get me?

As for the master cylinder as matts1 suggested, ive changed it for a mk4 90 spec cylinder, the mk3, and mk4 pre 90 specs have a 22mm master cylinder, mk4 90 specs have a 23mm, which is what ive fitted, and also changed aswell for one i know was definately 100%.

Just out of interest what was the solution to yours then, did you change the master cylinder, and if so what for?

Any other suggestions? I'm still yet to try re-bleeding the rear calipers dropped down, i was in some doubt when i bled them as there was still a couple of tiny tiny air bubbles. thanks for your suggestions however and i'll definately bear them in mind

SafeChav

ok re-bled the brakes, it would appear there was a little air in the back calipers, unbolting them so i could move them soon did the trick.

Pedal still has a little travel in it but now feels firm when u get so far down the travel. Has anyone else done this brake set up and if so did u experience this same sort of thing?

Wazzzer

got exactly the same setup and mines always been shite but I found the reason when taking the m/cylinder and servo apart, the O ring was fooked so I've never got the full potential out of them yet, hoping its gonna be good lol

SafeChav

does ur pedal have a a bit more travel than before? well i used a second hand master cylinder because i was in the experimental stages and forking out for a new one and then finding out its useless would of been well annoying, but the car it was on had a very firm feel to the pedal.

I must admit im now wondering whether it was such a good idea?u got a 22 or 23mm cylinder on yours? guessing 22 being an E plate, it should be on the side of the cylinder.

where u getting your seals from too, couldnt find any for love nor money, not from any local motor factors

cheeRS mate

matts1

Mine had more travel than it should have done, and when it was changed became worse so presume a 23mm was on before and then was changes to a standard 22mm causing the extra travell.

I lived with it but it was a pain in the wet as you became more likely to skid due to you having more trqavel then braking kicking in suddenly, and because it was a second car i never really became used to it.

May be worth looking into master cylinders with an even larger core, what is the size of a cosworth core?? may give a clue as to what is needed, if it is alot more than 22/23 then it may well be that, if not then look to something else as the cause

SafeChav

hmmm im not expecting quite as good results as i had originally hoped for

i dont know what size the cosworth ones are ANYONE KNOW?

im guna try having a fiddle with the nut in the servo tomorrow, hopefully that will reduce travel a bit, without causing the brakes to stay partially applied while driving.

hoping for the best

Wazzzer

not sure whats on it at the mo mate but the master cylinder is knackered so I'm getting one off a G plate ERST 2moro and I'll have to see

The O rings you can't buy from anywhere like Ford (they only sell them with a brand new master cylinder) or brake retailers so I went into a hardware shop and got one out of the plumbing bit