# MK1 GTI - master brake cylinder or booster?



## dburden (Mar 23, 2008)

The brake pedal on our '84 GTI went to the floor the other day. Nothing was leaking so I figured the master cylinder was shot. When I took it out, the plunger came out of the booster. The end in the master cylinder was rusted in place which I was able to remove with a little persuasion. The plunger part that came out was about 4 inches long with a round metal disk about an inch wide on the end that goes inside the booster. 

I put the new master cylinder in with the plunger, but the brakes are no better. The pedal still goes to the floor. Now I'm wondering if something broke inside the booster. Anyone seen this problem?

Thanks,
Dave
'69 Opel GT
'72 VW Bus
'84 Rabbit diesel
'84 Rabbit GTI


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## GTijoejoe (Oct 6, 2001)

sounds like a boost issue.. BUT... pedal going to the floor means you have no resistance? which means to line pressure? Of course no caliper, brake line, hose leaks right?


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## dburden (Mar 23, 2008)

I bench bled the new master cylinder then did a bleed on the system after installing it. I haven't had the chance to work on it this week, but did do some pondering. I'm going to re-bleed the whole system this weekend to eliminate the possibility of air in it. If the brake booster is shot, I don't have any problem running without boost, as long as the pedal is firm. 

Dave


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## GTijoejoe (Oct 6, 2001)

Yeah, the booster if self wont give any assist but the system should still be firm. Unless like the entire firewall is flexing or something crazy like that.


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