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grahamkissack's Avatar
 
Join Date: Apr 2004
Location: Vancouver Island
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MC install tips

Back in 2004 I did a full brake refresh with full caliper rebuilds (all seated properly now with pads within 0.5 mm of discs), new pads and with new mc and flexible brake lines. However, I never had good brakes...couldn't even bring the car into a skid....always felt like there was air in the lines. I did about 20 (seriously) brake bleeds via spouse pumping, gravity, pressure and vacuum approaches.....nada success...still poor results.

I've had enough and am going to do everything again. I have purchased a new mc and just pulled out the booster/mc assembly. First checked the booster with 15 in mg vacuum. After 15 minutes it was down to about 12 in mg...is that good enough or is it a leaky booster?

Second, I'm going to bench bleed the mc....how do I stop brake fluid from gravity bleeding out the mc ports while I install it in the car? Never bench bled before.

Third, does the brake pedal linkage adjustment in an 1980 sc do anything other than to move the brake pedal forward?

Any other thoughts before I move forward? Thanks.

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"Penelope" 1980 SC Targa in Grand Prix White

Last edited by grahamkissack; 07-11-2010 at 06:14 PM..
Old 07-11-2010, 06:09 PM
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I had big trouble too getting a good pedal on my 80SC. After using 1/2 gallon over several sessions I finally took the car round the block and got a good pedal within a mile. MI thought it might have to do with how the pistons flex in the seal rings, and the rattling the calipers get on the help them move.

Never had trouble with brake bleeding on any other vehicle before, except once where I did get a pedal after bench bleeding. I didn't expect bench bleeding to do any difference just did it to see see if the MC was working at all since there was so little fluid coming from the bleed nipples at the calipers. After the bench bleed I got a pedal immediately, so yes its worth doing.

I believe the linkage in our cars only affects position of pedal.
Old 07-11-2010, 09:35 PM
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Thanks...everyone talks about bench bleeding but not the specifics!
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Old 07-12-2010, 05:42 AM
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I don't know why they call it bleeding, because you're putting fluid in. It should be called bench filling.
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Old 07-12-2010, 06:15 AM
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Graham - did you ever exercise the calipers after rebuilding/replacing them? It's a trick my shop taught me after I installed new rear calipers and couldn't get a solid pedal (I use a Motive bleeder). Using an old set of pads (more worn out the better) and a pad spreader tool you simply push the pads fully in using the spreader and use the pedal to push them back out to contact the rotor. Repeat 5 times for each caliper. After that put new pads in and bleed the system, go around a couple times to be sure you see no bubbles. Try that before spending thousands of $$... If you already tried all this. move on.
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Last edited by GaryR; 07-12-2010 at 06:37 AM..
Old 07-12-2010, 06:33 AM
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Gary R. thanks for the tip. the pads are properly seated at the discs with just subtle friction but I'll give that a try too. Otherwise, I'm perfectly stumped...I've rebuilt many brakes before with no issues.
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Old 07-12-2010, 02:11 PM
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There is something about moving the pistons through their full length of travel that does the trick, which is why you want to use totally worn out pads to do it. Allows the pistons to come way out, then you push them all the way back in. It's the old in-out...

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Old 07-12-2010, 04:03 PM
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