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914World.com _ 914World Garage _ Brake Pedal Feel - Need some help
Posted by: porsche913b_sp Feb 1 2013, 07:45 PM
Is it suppose to feel hard on the first push. The pedal goes almost all the way down, then the 2nd and 3rd pump the pedal feels hard, but if I wait a few seconds the hard pedals goes away ?? Is this normal for an early 71 with 19mm MC or do I still have air in the system. I bleed it with the Motive Power bleeder and manual bleeding it with the speed bleeders. Is the problem with the speed bleeders ? I recently rebuilt all the calipers and install new lines, no leaks, but the MC is used though.
Let me know your experiences fellas ?
Ted
Posted by: kg6dxn Feb 1 2013, 07:57 PM
After the initial bleed the first few pumps may be soft. Later it should be firm. I think you still have air. You could try the old trick... Open one bleeder, push down on the pedal as fast as you can, then lift as slow as you can. repeat. start at the bleeder closest to the MC. End at the bleeder farthest from the MC. The fast pedal movement can help to force out the air. Slow pedal movement keeps it from moving back to the MC.
Is this a new MC? did you bench bleed it first?
Posted by: injunmort Feb 1 2013, 08:00 PM
make sure you are not leaking anywere first. then you can crack all the bleeders and top off m/c. let it sit that way overnight. close the bleeders and bleed starting at the caliper furthest away from master cylinder { right rear wheel first}}. i have my wife pump the brakes while i do the bleeders.work your way around, left rear, right front, left front. make sure you keep an eye on fluid level in resevoir. by the time you are done you should have a firm, steady pedal, no air inthe lines.
Posted by: JawjaPorsche Feb 1 2013, 08:30 PM
Just asking, are you doing it the old way with two people or are you using speed bleeders?
Posted by: rgalla9146 Feb 1 2013, 08:31 PM
After the initial bleed the first few pumps may be soft. Later it should be firm. I think you still have air. You could try the old trick... Open one bleeder, push down on the pedal as fast as you can, then lift as slow as you can. repeat. start at the bleeder closest to the MC. End at the bleeder farthest from the MC. The fast pedal movement can help to force out the air. Slow pedal movement keeps it from moving back to the MC.
Is this a new MC? did you bench bleed it first?
limey
Apply slow, light pressure to the pedal. If it slowly drops, you have a leak.
Most probably the master.
Inspect the area inside the pedal cluster for rust and slimey wetness. Pull the push rod boot off of the master. Slimy,wet ? Replace master. Rebuild the cluster while you're there
Posted by: rgalla9146 Feb 1 2013, 08:58 PM
After the initial bleed the first few pumps may be soft. Later it should be firm. I think you still have air. You could try the old trick... Open one bleeder, push down on the pedal as fast as you can, then lift as slow as you can. repeat. start at the bleeder closest to the MC. End at the bleeder farthest from the MC. The fast pedal movement can help to force out the air. Slow pedal movement keeps it from moving back to the MC.
Is this a new MC? did you bench bleed it first?
limey
Apply slow, light pressure to the pedal. If it slowly drops, you have a leak.
Most probably the master.
Inspect the area inside the pedal cluster for rust and slimey wetness. Pull the push rod boot off of the master. Slimy,wet ? Replace master. Rebuild the cluster while you're there
That "limey" up top is a typo.
Posted by: zambezi Feb 1 2013, 09:30 PM
Do you have the rear brake venting clearances set. That can cause you to have to pump the pedal to get some height out of it.
Posted by: porsche913b_sp Feb 2 2013, 01:38 AM
No I did not bench bleed the MC. I installed it dry 
I have speed bleeders on all four corners. Unfortunatley I dont have a buddy close by to lend a hand to help bleed the old fashion way. I may have to train my son to pump the pedal. I adjusted the venting clearance tonight and it helped a little but not a huge difference. It was kind of hard to slide the feeler gauge on the inside pad with the pad pins and spreader installed. I had to remove the metal spreader in between the pads to slide the feeler gauge on the inside pad. I dont see any leak near MC or the pedal cluster or anywhere else. I do need to adjust the brake pedal rod clearance to the MC. I had the pedal cluster out doing an overhaul. I thought the power bleeder would do magic.
Posted by: Eric_Shea Feb 2 2013, 08:42 AM
Other way around.
You can "edit" your posts you know...
Not a problem really.
It should really... OK, let's go through a check list:
1. Bleed furthest to shortest distance.
2. Tap lines and calipers with a plastic mallet or the wooden handle of a standard hammer while you bleed.
3. Adjust the pedal clearance/master cylinder rod.
4. Make sure the venting clearance is adjusted to .004"
5. Get a decent pedal and bed the pads.
6. Bed the pads again.
7. Bed the pads again and drive the car.
What happens "VERY OFTEN" (as in, almost 100% of the time) with a new caliper rebuild is this; the new seals are aggressively pulling the pistons back off the pads and rotors. Even a small amount will cause a soft pedal feel. As you bed the pads, you will heat up the calipers and the seals and they will break in. As the seals brake in, your pedal will begin to come back up.
Follow this procedure:
http://www.pmbperformance.com/bedin.html
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