My brakes don't start to grab until the brake pedal is pushed beyond the plane of the gas pedal, then they grab normally. I put a new master cyllinder on (actually 2), new front pads & checked the calipers, new rear pads last year and checked the calipers, and last night re-bled the whole system for the 25th time. Most of the time if I'm going down a hill, the pedal grabs about an inch higher. Could this be a booster/vacuum issue? It doesn't take more effort, but when going down a hill, the pedal grabs sooner. If I unplug a vacuum line 5 minutes after I shut off the car, I can hear the line sucking air in, so I know the car holds vacuum. My cam is pretty mild, so I should pull plenty of vacuum. It was like this with the stock 305 too. They have been like this since I bought the car. Please help!

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"I didn't know a bored out Ford could go so slow" -Shenandoah

 

If you had drum rears, I'd suggest adjusting up your shoes. Sounds like you have disk rears, and I'm no expert on them. But, from the symptoms, it sounds like there is too much gap between the pads and disk somewhere in the system, and that gap is taking almost all your pedal travel to take up. Since you say it doesn't take any more effort once it grabs, it doesn't sound like a vacuum issue.

You might try posting on the Suspension/Chassis/Brakes board for better advice.

If this started with the master cylinder replacement, I wonder if you got the wrong part (twice). Too much free travel, perhaps?

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Try working your parking brake up and down a few times. It adjusts the rear calipers to the rotor to reduce the gap. Maybe when you redid your rear pads, the pistons were pushed all the way in and they didn't return.

 

I have the same exact problem, and I did the same exact things you have done, What I did when I had the old style brakes is, adjust the e brake good a tight and that seemed to help alot, now I have the pbr calipers and it is doing it again but I think I need new rear rotors.

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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

 

I use the e-brake on occasion, and even when I yank it up with 2 hands, it hardly holds well enough to stop the car from rolling. There's no chance of it holding back the motor when it idles. It's got new cables, blah blah blah. I hate these rear disks.

I'm on my 3rd master cyllinder (including the original) and nothing has changed at all. No better, no worse.

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The IROC Homepage
<A HREF="http://www.rit.edu/~jli4307/camaro" TARGET=_blank>
View the restoration of an 85 IROC</A>
"I didn't know a bored out Ford could go so slow" -Shenandoah

 

hows the proportioning valve? did you replace the rubber hoses? any time i have brake probs i just start replacing everything and it usually gets fixed...but then again i usually dont pay for my stuff also try adjusting the e brake cable...then in turn your rears can be adjusted and that might solve it or get rid of another possibility.

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350, Comp 262, Edelbrock Performer intake 600 cfm carb and exhaust, headers

 

I haven't fooled with the prop. valve yet. I didn't figure that would account for a sloppy pedal. The rubber lines on the front are pretty good. The e-brake is adjusted so that it pulls about 2 inches then starts giving resistance, and I can only pull it to about a 35* angle.

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The IROC Homepage
<A HREF="http://www.rit.edu/~jli4307/camaro" TARGET=_blank>
View the restoration of an 85 IROC</A>
"I didn't know a bored out Ford could go so slow" -Shenandoah

 

One thing you'll not hear mentioned very much when it comes to breaks is the use of rubber lines vs steel braided. Russell makes some steel braided lines just for 3rd gen F bodies. They claim they will provide much firmer, more responsive breaking. Summit carries them for $74.95. good luck.
Jim

 

Before I start throwing aftermarket crap at my brakes, I want them to work as General Motors intended. I know that things like braided hoses can make a small difference in pedal feel, but I've driven enough bone stock thirdgens to know that mine needs VAST improvement to even get back to normal. Unless the rubber hoses are bloating to 5x their original size, they aren't the problem.

 

this may be a dumb question especially after you have bled the brakes 25 times but how are you bleeding the brakes. It sounds more like air in the line if the pedal is going down that far. Are you doing the good old method of one person holds the brake pedal down while the other loosens the fittings at each wheel so no air is sucked back into the line? If your using one of those nice one man brake bleed kits the whole time, try doing the old way one time just to be sure it's not air. Good luck!

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1988 TA 300+hp 350 w/ TBI and Holley TB unit, Holley projection intake,
WC T-5, 3.42 gears w/ Auburn posi. MSD 6A, edelbrock TES headers, dynomax 3" cat and cat-back system, ACCEL coil, polyurethane bushings all around, aluminum driveshaft, Mr. Gasket open air cleaner.

1993 S-10 w/ 4.3L V6 TBI, slightly bigger cam, Mild polish job and 3 angle valve job on heads, Edlebrock TES headers, Dynomax cat back, MSD 6A, ADS chip

2000 Kawasaki KX 125

 

My dad and I are doing it the old fashioned way. He pumps 3 times and holds. I open the bleeder until the pedal hits the floor, then close the bleeder and repeat a bunch of times. I don't get any sorts of air gaps or spits or sputtering or anything like that, and I've done it so much that clean fluid is coming out.

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The IROC Homepage
<A HREF="http://www.rit.edu/~jli4307/camaro" TARGET=_blank>
View the restoration of an 85 IROC</A>
"I didn't know a bored out Ford could go so slow" -Shenandoah

 

Jim,

It sounds as if your bleeding procedure is correct. It also sounds as if the hydraulic system and power booster are functioning normally. If the pedal feels normal without being soft, and requires the same effort to stop the vehicle (but with greater free travel), the liklihood of a soft hose is neglible. Since you have discs all around, the clearance problem is a good path to pursue.

The rear calipers on our cars have notorious problems with sticking. The park brake cables and actuator screws MUST be free and the calipers MUST be allowed to float in their brackets so that clearance is kept to an absolute minimum. The same holds true for the front calipers. They must be floating in the brackets to allow even actuation. All the extra clearance is additive, and will require additional pedal travel before the brakes are effective. Once the free space is taken up, the brakes will function normally - just as you describe.

Another cause of excessive clearance is warped rotors. When the brakes are relaxed, the runout of the rotors will push the pads farther away from the rotor than should be necessary. This can be checked with a dial indicator and base. While you're checking, measure the rotor thickness in several places around its circumference to check for even wear. If the rotors are warped or have runout, the only solution is to machine them flat or replace them.

If the rotors are O.K., the calipers need cleaning, lubrication, and possible repair of the park brake mechanism. I use my park brakes EVERY time I park a vehicle just to make sure the mechanisms stay free. My engine will not overcome the parking brake when set firmky with one hand, including the POS rear calipers on my '86 TA.

Once you're certain the rotors are straight and true, and the calipers are operating correctly, there won't be much left other than a master cylinder problem. The proportioning valve generally won't cause the kind of pedal travel symptoms you describe if the master cylinder is pumping correctly - all the fluid has to go to some part of the brake system. Since you're on yout third master cylinder, I'd guess the problem is not there. By process of elimination, the likely cause is excessive clearance.

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Later,
Vader
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