xsara hdi master cylinder??? please help

simonelsey · Post by **simonelsey** » 02 Apr 2007, 19:29

Well Ive got to bite the bullet and Ive got to replace my master cylinder , its one of the last mk1s HDis with lucas c54 calipers .(as im really fed up with the brakes on one side driverside wearing + possible rear left wearing slighlty more

)

How much much should I pay for item ?

Ive done a web search and cannot find. Can find on prnet but a bit juicy

How much to have fitted ???

Any help would be great ,

PS As some of you may have read my posts over past 18-24 months Ive replaced the caliper and hoses on the front so this is the last straw for it .Other wise its going .

jeremy · Post by **jeremy** » 02 Apr 2007, 20:52

Have you got excessively long pedal travel? If not I don't think its the master cylinder.

simonelsey · Post by **simonelsey** » 02 Apr 2007, 21:16

doesnt seem like long travel . THen again I may be just use to it , Its passed every MOT with it , I just change the pads before MOT and she passes all ok .

jeremy · Post by **jeremy** » 02 Apr 2007, 23:11

I think your original suggestion is that as the front pads on one wheel wear more rapidly then its due to failure of the master cylinder.

I think the Xsara has diagonally split brakes which are operated by a tandem master cylinder sitting on a direct acting vacuum servo. The tandem cylinder keeps the 2 circuits separate by having 2 pistons in a common bore. The 2 pistons are separated by fluid in the bore and various springs. Basically fluid alone is trapped between the two pistons - so pushing on the back one operates one circuit and also pushes the front one which in turn operates the other circuit.

So if the front circuit leaks - the front piston hits the end of the cylinder and the back piston still functions. If the back circuit collapses - the back piston moves till it collides with the front piston and operates the front cylinder normally.

Thus if one circuit collapses - the pedal moves a long way - and I mean a long way. I had one collapse on my Renault 21 when a back brake stuck on and boiled the fluid - and I can assure you its very noticeable as the pedal seems to hit the floor!

David W · Post by **David W** » 03 Apr 2007, 07:45

I note you say it passes the MOT OK. Surely their brake balance rollers would show this up. They are usually quite sensitive to any imbalance in effort.

David

simonelsey · Post by **simonelsey** » 03 Apr 2007, 21:26

David W wrote:I note you say it passes the MOT OK. Surely their brake balance rollers would show this up. They are usually quite sensitive to any imbalance in effort.

David

Quite right but doesnt show any thing up , so at a complete lost . been like it at 3 mots .

I just dont understand it .

Im very cofusued with it .