Occasionally losing brake pressure

[Gazb]

Occasionally when driving along my brake pedal has no resistance and goes almost to the floor and you need to pump it again before there is brake pressure and the brakes work.

I've checked the brake fluid level and its is within the max-min levels, however I know that it is losing brake fluid.

On further inspection I noticed that there appears to be brake fluid leaking around the rubber grommet (closest to the bulkhead) where the reservoir attaches to the master cylinder.

My question is, how come I occasionally lose brake pressure even though there is plenty brake fluid in the reservoir?
Is the grommet occasionally moving and fluid is just being pushed out or is he master cylinder shot and just needs replaced?

[davey670]

i would replace that master cylinder a.s.a.p
even if its full of brake fluid you may be dragging in air past that rubber seal in to the master cylinder as you lift your foot off the brakes and that will make it go direct to the floor mext time you push the pedal as its pushing air first then the fluid

you should not drive the car like that as the brakes will fail on you at some point if too much air gets in to the system.

[Gazb]

i would replace that master cylinder a.s.a.p
even if its full of brake fluid you may be dragging in air past that rubber seal in to the master cylinder as you lift your foot off the brakes and that will make it go direct to the floor mext time you push the pedal as its pushing air first then the fluid

you should not drive the car like that as the brakes will fail on you at some point if too much air gets in to the system.

Yeah I haven't moved the car since. I'm driving my daily (Ibiza Cupra TDI) atm.

I've noticed that there is 2 master cylinder's listed for a 1990 gti 16v on GSF.

PN: 65276
Description: BRAKE MASTER CYL-22.2mm
Fitment: G2 16V 12/88 >10/91
Price (£): 34.20

PN: 65277
Description: BRAKE MASTER CYL-FAG 22mm
Fitment: G2 16V 12/88 >10/91
Price (£): 54.00

I'm curious if the price difference is more than because its made by a different manufacturer.

[Crasher]

Go for the more expensive one, the cheap white box items are not nice. Your car has two outlets and the new MC has four, make sure it comes with the two blanking plugs.