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#11
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What Kurt said about preloading the pistons has done the trick for me in the past. This past weekend I had an interesting issue in the Miata. Pads were worn so replaced pads (not rotors which are pretty new, didn't crack the bleeders, very recent fluid change. Then, l-o-n-g pedal on a hard brake (fine for normal). Brakes worked but scary (fortunately I tap my brakes leaving the pits so I noticed before I was at speed. Bret (shop next to Billy's at SP) and I believe it was one pad hung up on the locating clip (those who have only changed Porsche brakes won't know what I'm talking about) so hadn't seated completely but was on the rear side and didn't show. Multiple pumps only partially firmed the pedal. But multiple hard pumps by Bret resulted in an audible click and then they were fine, so that's what we figured had happened.
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Peter (not "Pete") K. 2016 Cayman S 1999 Miata ("SM") race car 2016 Toyota Highlander--tow vehicle/wife's DD 2017 VW GTI SE (DD) Gone and missed: 1992 Miata ("SSM") race car 2009 911 C2S Coupe 2004 Toyota Prius - sold to son's girlfriend 2006 Dodge Durango 2003 Acura MDX 86 Black 911 Coupe race car 86 Gold 911 Targa 82 WineRedMetallic 911 Targa |
#12
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Quote:
I ran another can of ATE through it last night, made sure everything was tight. Put it back together and took it around the neighborhood. The pedal does not instill confidence, so I'll have to wait until early morning on the weekend when there is less traffic to drive it any real distance. Not a good feeling when you have to push that pedal MUCH farther to get the car to stop
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_______________________________________________ Tim M '00 C5 Corvette FRC track car '86 944 N/A (aka Doublemint) - Past '20 Ford Expedition Max |
#13
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Drive it for 100 miles or so or reset the pads/seals. If that does not do the trick you might still have a bubble somewhere.
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http://vimeo.com/29896988 “Those that can make you believe in absurdities can make you commit atrocities.” Voltaire. "There is grandeur in this view of life...." Darwin. The mountains are calling and I must go. “The earth has music for those who listen” Shakespeare. You Matter. (Until you multiply yourself times the speed of light squared. Then you Energy) “We’ve got lots of theories, we just don’t have the evidence’. |
#14
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All of the advice so far is spot on as usual. But one thing I'm not sure of is when you say, "I ran a can of fluid thru", what is the procedure you are using? Motive pressure bleeder, vacuum bleeder, the old two person push the pedal down, crack the bleed screw, close and lift up the pedal? The reason I ask is sometimes I have found you need to get velocity in the lines to get bubbles out of the top of the system and especially the loop of the hose from the frame to the strut. Best way I have found is the fast pedal movement to the floor. The other thought I had is the condition of your soft lines. By disassembling and moving things around you may have cracked the outer layer resulting in a bulging hose. Get somebody to push the pedal and observe the lines for flexion. If you have not replaced them now is the time. Braided lines offer some protection from abrasion and tend not to flex as much. The only other thing I can think of and I can't remember is if the seals are tapered. If so you might have them in backwards resulting in pullback. I'm pretty sure they are cut square though. Last thing is to make sure you oriented the piston with the 20 degree tool to insure even pad wear.
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Steve Potomac PCA Co-CI(retired) 89 944 Turbo Race car 85.5 944 NA son's 2015/2019/2020 944Cup and PCA Nat'l Champ racecar 94 968 1 of 11 Iris blue coupes 92 968 1 of 2 Tahoe Blue Cabriolets 98 993 C2S w/Aerokit II 77 911S Vintage race car project 70 Boss 302 86 Mustang SVO 08 F250 SD Diesel 15 Audi SQ5 "Noel spun! Noel spun! Don't do anything stupid, Dad." -the boy on the radio on the last lap of NASA race as the second place car spins behind me in T5 at Summit Point. |
#15
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Seals - hmmm, is the yellow mark on the new seal supposed to sit against the inside of the groove in the bore, or against the wall of the piston? I did the latter.....I thought they were square as well.
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_______________________________________________ Tim M '00 C5 Corvette FRC track car '86 944 N/A (aka Doublemint) - Past '20 Ford Expedition Max |
#16
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Update: I was able to get a little heat in them one Sunday a couple weeks ago on the way down the mountain on Route 7 West of Leesburg.....it helped. They don't feel quite the same as they used to, but much much better certainly. Thanks!
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_______________________________________________ Tim M '00 C5 Corvette FRC track car '86 944 N/A (aka Doublemint) - Past '20 Ford Expedition Max |
#17
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UPDATE: I ran the Shenandoah event and on Saturday the pedal travel was still a little long and did not inspire confidence, but the car was stopping ok. I don't think they stopped quite as well as last year and before I swapped the calipers, but they were about 90%.
After each session that day, my brake fluid reservoir would drop about 1/4". There would be a little dampness on top of the cap, but not enough to explain the 1/4" drop. All four corners were dry, and I could not find a leak anywhere. Sunday on the out lap, my car belched a giant cloud of oil smoke when upshifting to 4th coming out of Big Bend (slightly overfilled oil I believe, it did this one other time a few years back). Oil pressure was fine and no leaks. But while looking for oil leaks in the paddock, I noted brake fluid around the area under the MC and the booster. Then found the bulk of it coming out the weep hole in the bottom of the MC. Should replacing the MC should fix this, or something more involved with the booster?
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_______________________________________________ Tim M '00 C5 Corvette FRC track car '86 944 N/A (aka Doublemint) - Past '20 Ford Expedition Max |
#18
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If fluid is leaking from the MC, replace it. Booster is probably fine as fluid does not interact or flow through it. Might be a good idea to have a mechanic look at it. Never want to screw around with critical safety things like brakes.
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Steve 2009 Cayman S |
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