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? |
technicalninja |
May 20 2024, 11:05 AM
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#2
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Senior Member Group: Members Posts: 1,851 Joined: 31-January 23 From: Granbury Texas Member No.: 27,135 Region Association: Southwest Region |
The vent clearance has to be tight!
If the rotors are dirty from sitting get the system up, run the car around a bit (re-bedding pads and cleaning up the rotors) and hit that vent clearance again. The square cut caliper seals get old and sometimes will not allow for proper piston retraction. You end up with brakes that slightly drag and wear pads out quickly. Same age points as lines. 20-year-old calipers SHOULD be rebuilt. I've got a new "add" that I'm going to do when I put mine back together. Get everything proper and have a reasonable pedal. "Kick the dog shit" out of the pedal to ACTIVATE the rear pressure regulator three or 4 times. Re-bleed rear. ABS bleeding tip: Find a pea gravel parking lot and ACTIVATE the abs circuits! Clears those bubble gremlins right out. Don't do this when the owners of the parking lot are present! Clean up the ruts... |
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