Brake master cylinder query!

[Veedubgt18v]

I went into a brake shop for a brake test today, the guy 'brake tested' it by clamping off all the hoses and then pressing the pedal, it moved down about an inch and a half, the guy said this was because my master cylinder seals had gone because of the high water content in my brake fluid (it boiled at 128 degrees c). he said i would need a new one! is this right and how expensive roughly?
cheers peeps
ed

[Veedubgt18v]

Also is there a different master cylinder i can fit that will give better feel/power etc?

[golfvr6]

You may be able to use a 16v master cylinder, which is bigger i think.
They don't come cheap mate, if you want a genuine one you will be looking at near 200 bar i think. Thats unless VW have dropped the prices on them.
You better bring her round mate, never trust a mechanic  

[turbo]

this could just be the brake fluid dont forget you wont get a pedel which wont move down an inch because of hydrolic pressure build up!!!!

if your master cylinder is faulty your pedal will hit the floor and you wont be able to build up pressure!
each time you press it it would fall to the floor!!!!!!

there is normaly a limit to how much pedal movement is allowable......... my 8v gti mk 2 has probibly more pedal downwards movement than 1" mk 2 brakes will always feel flat and spungee ive fitted the metal braided hoses and changed the fluid and it doesnt feel any better the only better braking i found was when i got some ate powerdiscs and pagid pads it stops better but nothing like the vr6 brakes!!!!!! and there standard!!!!

unless the pedal is nearly hitting the floor just change the fluid! you will know when your master cylinder has had it because your foot will go to the floor!!!!
but it wont do this sudden it will get worse of a period of time!

if your unsure of how much pedel excess is allowed ring up your local dealer and ask them!!!!!

i'm sure your master clyinder is fine!

[Veedubgt18v]

cool cheers guys, thought i would ask as brakes can be dodgy! 6 i found a price for 8v brake master cylinder from eurocarparts for just under 40bar? would the 16v one really make a difference or am i better off spending the money on something else?

[Veedubgt18v]

also can i fit a master cylinder off of a driver cos i can get one of these for free, i expect not but it doesnt hurt to ask!  

[modulater]

I think you need to tell us why your getting your brakes looked at in the first place. What problems are you having?

As said above by vw systems the pedal will move down about an inch as you make pressure in the master cylinder, otherwise your brakes would be on all the time.  stop the engine and build up pressure by pumping the pedal a few times.

When you push on the pedal does it move down?

I would not replace the master cylinder as this is unlikely, just pressure change the brake fluid and make sure all the brake hoses are in good condition and not bulging.

If the seals have gone why buy a new cylinder, just fit a seal kit.

Also clamping off all the hoses and pressing the pedal sounds like a incompetent way of testing the brakes. As it is completely cutting off the calipers and so a fault in these wouldn't be shown. A decent shop would have put it on brake testing rollers.

I think they saw you coming mate.

[modulater]

Brake fluid is hydroscopic. This means that it absorbs moisture. So over time the brake fluid will contain moisture.

The amount of water you have in your brakes tells me that the brakes on your car haven't been looked after very well and if you have that much water content in your fluid then you must have a faulty reservoir cap seal that is letting abnormal amounts of moisture in.

Change the brake fluid as this sounds like is needs doing urgently. Then check the solid and flexible lines to check they are ok.

I think the fluid change will solve your problems.

[Veedubgt18v]

i think the brakes have been looked after but the other day i noticed the lid on the pot had been cross threaded and kept faling off so for a while the lid had been off which would explain the moisture
goin round to see mr6 now anyway

[golfvr6]

i would say the brakes just need a good bleed.
unfortunately most garages can't be trusted