Might have a bad Master Cylinder

[8v-of-fury]

So I was thinking if I need to replace it, I'll probably upgrade it at the same time and get a bigger bore one for shots and goggles.

Now, I recall I had a parts car that I used a master out of.. It was a 1998 TDI, so I believe that was a 22mm. I used it to replace a failed master on a 1990 8v gas, which I think had a 20mm.

SO! I need to replace the one on the 88 1.6 TD now me thinks, as I have brake pedal fade while holding the pedal ( I will be bleeding maybe tomorrow, before I purchase a master ). I just wanted to get some ideas, will the 22.20mm Dia from a 96 2.0L work??

1996 2.0L Gas 22.20mm



1988 1.6 TD 20.64mm



Pictures make it looks likes it wills works. Only $18 more for the big bore too..

[bbob203]

literraly came to post a thread about this   I also need to do a fluid flush and install the ss braided brake hoses I purchased years ago. must be a glitch in the mk2 matrix I'm having same problems with my brakes.

[bajacalal]

I have done the "mk3 master cylinder on a mk2 car" upgrade. Yes it fits and it's slightly bigger, and locally, the price for the mk3 master cylinder was less than the older 20 mm unit which was not in stock locally. So it was really a no-brainier.

[bbob203]

I have done the "mk3 master cylinder on a mk2 car" upgrade. Yes it fits and it's slightly bigger, and locally, the price for the mk3 master cylinder was less than the older 20 mm unit which was not in stock locally. So it was really a no-brainier.

did you feel a difference?

[8v-of-fury]

I recall when I did the 22mm in the 90 gasser it made it so you had to push the pedal less to have the same braking power.. which would make sense as you now have more leverage hydraulically over the brake fluid..

22mm seems the way to go.

[cyrus #1]

A 22mm master cylinder will give you a shorter pedal travel but require more force on the pedal to achieve the same amount of stopping power.  I don't see that being an issue for most of us on the forum.  I'm sure most here would prefer the less spongy feel.

I did a pretty big brake upgrade on my MKII gasser a couple of years ago as I was having the exact problems that you are describing.  It was to the point where I couldn't even bleed my rear brakes properly.  I ended up finding a rock slightly larger than a marble wedged in the proportioning valve that was obstructing its motion.  After prying that out I was able to bleed the system properly.

[8v-of-fury]

Hmmm.. thats insane. I have not yet bled the rear brakes on this car. Picked it up in August, and checked them out back there.. the cylinders were not weeping, so I did not risk braking the bleeder at that time lol. I will most likely be putting it in the air tomorrow and bleeding the rear.

The front has fresh DOT4 from when I did the vented rotor swap up front. Being that they are spongy, and they take a little while longer to heat up.. it makes for a weird feeling trying to stop lol.

[bajacalal]

did you feel a difference?

Considering I also, at the same time, replaced the rear drums with disc brakes, upgrade the fronts and installed vented rotors on all 4 corners with racing pads, and replaced all hydraulic hoses (one rear was plugged), I can't really say what effect the master cylinder had specifically, because the difference made by ALL of this stuff was astounding.

[wolf_walker]

If this is a keeper car, think real hard about spending the money on a genuine German master cylinder.  I have replaced more generic McParts store crap examples than I can remember.
The German one will last twenty years if you flush the fluid occasionally.