Me vs. Brakes: The Road to a Solid Pedal Options

[Bwingate]

I have been fighting mushy brakes since I got my 914. They are better but not great. I suspect there is a lot more bleeding to do, including finding the proportioning valve to bleed.

The PO said that they had the master cylinder changed by a local "Porsche expert" I suspect it was replaced with the 17 mm master cylinder. Can I confirm with an external inspection whether it is a 17 mm or 19 mm MC?

So my plan is:
1) Bleed MC
2) Bleed proportioning valve
3) Possible replace soft lines
4) Bleed each wheel again.

I saw something on this site that made sense, but I had never seen it before: Clamp off all the soft lines and test the pedal. If the pedal is solid, then the problem is at the wheels; if the pedal is soft, then it is the MC. Then unclamp each wheel one at a time - the "bad" wheel will be soft, the "good" wheels will have a firm pedal. Is this a bad idea?

[iankarr]

You've gotten great advice in this thread. Also important to keep in mind that it's normal with these cars/calipers for it to be a bit of work to get firm pedal when the system is fresh. There are literally dozens, if not hundreds of threads about trying to get a hard pedal. Just to summarize, in order (with a few things that have worked for me)...

– "Bench Bleed" master cylinder if not already done (see video in my signature for how)
– Replace rubber lines
– Ensure venting clearance is correct
– Replace bleeders with speed bleeders
– Use a motive pressure system AND stomp on the pedal (this is where the speed bleeders really help)
– Repeat bleeding 2-3X
– If pedal is too soft to drive, crack the fittings on the regulator and pump pedal (closing after each pump) to get air bubbles out. Can also tap with a hammer.
– If pedal is STILL too soft, try using a syringe to shoot fluid through the bottom bleeder, with the upper one open. This forces stubborn tiny bubbles out.
– Take the car for a bumpy drive
– Bleed again
– Bed the pads
– Pedal will not be rock hard for about 100 miles or so...until the seals loosen up.

Hang in there!

[wonkipop]

You've gotten great advice in this thread. Also important to keep in mind that it's normal with these cars/calipers for it to be a bit of work to get firm pedal when the system is fresh. There are literally dozens, if not hundreds of threads about trying to get a hard pedal. Just to summarize, in order (with a few things that have worked for me)...

– "Bench Bleed" master cylinder if not already done (see video in my signature for how)
– Replace rubber lines
– Ensure venting clearance is correct
– Replace bleeders with speed bleeders
– Use a motive pressure system AND stomp on the pedal (this is where the speed bleeders really help)
– Repeat bleeding 2-3X
– If pedal is too soft to drive, crack the fittings on the regulator and pump pedal (closing after each pump) to get air bubbles out. Can also tap with a hammer.
– If pedal is STILL too soft, try using a syringe to shoot fluid through the bottom bleeder, with the upper one open. This forces stubborn tiny bubbles out.
– Take the car for a bumpy drive
– Bleed again
– Bed the pads
– Pedal will not be rock hard for about 100 miles or so...until the seals loosen up.

Hang in there!

that pretty much describes my experience back in early 2020 after laying the car up for 16 years. (IMG:style_emoticons/default/biggrin.gif)

and even then its not a firm pedal like modern cars. i think part of it is its meant to be a little soft so you can use your foot with a bit of sensetivity? ....... and not lock up rear brakes. the old proportioning valve thing? dunno. but mine will pull up pretty good and pretty straight with a firm stand on the pedal. but its firm---ish and the pedal goes down. a ways.
they are actually pretty good brakes,,,,,,,,for 1969.
try a type 3 VW from the same era and count the number of circles you do if you stand on the brakes with the same force. (IMG:style_emoticons/default/beer.gif)