Me vs. Brakes: The Road to a Solid Pedal |
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Me vs. Brakes: The Road to a Solid Pedal |
Bwingate |
May 20 2024, 07:25 AM
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#1
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Newbie Group: Members Posts: 19 Joined: 30-March 24 From: New York Member No.: 28,029 Region Association: North East States |
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 |
May 21 2024, 09:05 PM
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#2
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The wrencher formerly known as Cuddy_K Group: Members Posts: 2,484 Joined: 22-May 15 From: Heber City, UT Member No.: 18,749 Region Association: Intermountain Region |
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! |
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