Brake Help!

[Rowey1]

After a bit of advice really, I’ve recently upgraded the brakes on my Peugeot 206 GTI 180 to 304mm 207 GTI discs, calipers and braided hoses, I ran them for a year and although the brakes worked well I was told that increasing the size of my master cylinder would help. I changed the master cylinder to a 23mm Peugeot 306 one and I’m now struggling to bleed the system to the point I get a good pedal. I’ve bled all four corners and have cleared all air from the calipers, I’ve activated the ABS pump using diagnostic machine. My O/S/F wheel has pressure and fluid there but won’t lock up. I’ve had to use an M12 to M10 adapter on one of the pipes to get it to fit the master cylinder would this cause it to lose pressure? Anyone got any answers for me?

[Mave]

Have you bled the new master cylinder?

[The Wookie]

Bleed the master cylinder on the bench, they’re a pain to do on the car.

What sort of adaptor did you use? Did you use a copper gasket on the mating face for the master outlet? If it isn’t sealed properly it can draw air in when releasing the brakes

ETA the larger master will make the pedal shorter and harder, better is subjective. 23mm is quite big, how much larger is it than the original?

Also I wouldn’t like to guess what the ABS is doing with the different sized caliper and discs...

Edited by The Wookie on Tuesday 6th November 21:32

[Rowey1]

Yes i used a copper washer to prevent any fluid leaks on my adapter and the outlet where it bolts to the servo has a rubber seal, I'll have to try removing the master cylinder and bench bleeding it and then just repeat the process when its on the car and see how i get on.

My original master cylinder was already 22mm but was also faulty and i thought whilst i was replacing it anyway i'd try the 23mm one.

Thanks for the advice.

Edited by Rowey1 on Friday 9th November 18:23

[The Wookie]

Ah I forget, tandem cylinder, they’re larger than the individual ones on the biased pedal arrangements I normally deal with. Wouldn’t have thought 1mm would make too drastic a difference and cause an issue