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Brake problems.

About four years ago, I noticed my brakes went a little soft after my first auto-x.

I bled them with little change. So I changed flex lines about 2 years ago. Changed the pads to Metal Masters in the front, and Pagid's (street) in the rear. I asked Pelican for a more aggressive rear pad. I think I got that right.

Still same situation.

Changed M/C about 3 months ago.

Same situation.

Rebuilt Calipers yesterday.

I still have a 1" free play then 1" squishy pedal. The last 1" seems to hit a solid place at the end of the 1" travel and then the brakes will really start to work.

I have it on jack stands, and I can put it in 1st gear, idle it, and stop the driver's rear from spinning. But I can't stop the passenger's rear from spinning no matter how hard I hit the pedal. I notice the pedal goes softer the harder I hit it. Then it returns to the normal 1" squishy.

I am expecting a ROCK SOLID pedal. Is this not the case?

Could it be my bleeder valves?

I hit the front rotors lightly with a disc sander to take off the glaze. I didn't do the rears.

I took the front pan off (under the steering rack) and followed ALL the brake lines to each caliper and there is nothiing wet.

What's left???

Thanks

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Old 06-16-2003, 07:24 PM
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What method of bleeding did you use??

Are you saying that the rear passenger caliper can not stop the wheel from turning at all if so piston is frozen or if the car has a proportioning valve it might be bad or there is something in the line that is preventing fluid from getting to the caliper.

I will assume that you rebuild all of the calipers. If it were me I would pickup a pressure bleeder and rebleed the entire system, open up those bleeder valves and hit the calipers with a rubber mallet while bleeding.

After bleeding, pull the pads from each caliper, one caliper at a time and insert old pads that have less than 1/2 of brake material or 2 pieces of wood between the rotor and piston. Have some GENTLY apply the brakes so that the pistons are forced out of the calipers further than with the newer pads. Carefully press the pistons back in the caliper and re-install the new pads.

If that doesn't help, you have problems beyond my abilities while at long distance.
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Old 06-16-2003, 08:17 PM
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Thanks for the reply.

Sorry - I was trying to keep my first post short.

No prportioning valve, that I could find anyway. I also looked through Pelican's array of brake lines, and did not find a proportioning valve.

I do have a black thing near the M/C in the trunk. It's under a small carboard piece. There is no fluid here either. Someone suggested it is a pressure valve for the front brakes???

I have the Motive Power Bleeder.

TODAY - I have gone through 3 1/2 quarts now. As opposed to other days with 2 quarts.

With bleeder open (on each caliper), I have tapped on the hard line near transmission, tapped on flex-line, tapped on hard line on caliper, and pounded the caliper silly.

Yesterday, I had a helper pressing the brakes. Still no go (or stop).

I have switched my rear caliper's bleed screws with each other. I am able to stall the engine, if I hit it REALLY HARD AND FASt. But not if I slowly hit the brake pedal..... maybe this is good?

SOOOOOo maybe I need some bleed screws...

The pedal is feeling better. I think I will try bleeding them all again (another quart).

Anyone else with some suggestions???
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Old 06-16-2003, 08:26 PM
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Anyone else?
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Old 06-17-2003, 07:13 AM
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The thing inline under the cardboard thing does limit pressure to the rear tires under very hard braking. I would expect the rear brakes to stop both rear tires period. If your passenger's side rear is still not stopping then you have a serious problem there. When you bleed the brakes are you bleeding all four starting with the right rear, then left rear, then right front, then left front?

If you are getting a mushy pedal, you have done lots of work to the front, but the back right is not working, then have you done lots of work to the rear, that corner especially?? Did you replace all four rubber lines? It sounds like there is a problem with that rear caliper or something. Maybe the pressure limiting valve is limiting too much pressure to the rear.

I don't know, but I would definitely keep working on it.
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Old 06-17-2003, 07:28 AM
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Thanks for the reply.

I have replaced all four flex lines.

The rear brakes appear to be working correctly... but not if I slowly hit the brakes. Only when I hit them hard will it still stall the engine in first gear.

BTW: The pedal feels HARD now with the Power Bleeder on it and having pressure. With it off, it feels a little mushy but better than before.

What more can I do? Two more quarts of Brake fluid?

Thanks again.
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Old 06-17-2003, 07:35 AM
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AAAAAAAAAAAHHHHHHHHHHHH

I AM GOING TO SELL IT!!!!!!!!!!!



Driving around today, the pedal does it's normal 2" travel before the brakes really start to work. I have hardly any confidence in these brakes.

I can pump up the pedal and it feels good - and seems to brake well. But it will only last one time for braking....

Is it a BAD M/C still????

Or is it "simply" a matter of resetting the pads?

Maybe I got too much brake fluid on the pads?

Anyone?
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Old 06-17-2003, 09:51 AM
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Ours had a similar mushy feeling and it turned out to be the brake booster. You can check this by putting your foot on the brake with the car OFF. Then, start the car and the pedal should try to push your foot up a little. If it doesn't, your brake booster is probably bad. I'm not sure about the weak caliper though???
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Old 06-17-2003, 10:24 AM
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I am convinced you are experiencing the typical settling in of the new calipers, especially if you have put in new brake pads.

New caliper seals love to drag the puck back to the "last found" position. If this was deep in the caliper than it stands to reason that you must pump harder to get the pucks out that then engage the pads which then touch the rotors. That is why one poster suggested "pre-loading" the brakes by removing the pads and over-setting the pucks. By moving the pucks out, then pushing them in JUST ENOUGH TO BARELY get the pad in, you essentially take the slop out of the system. The degree of internal slop your foot is feeling is undoubtedly part air in the fluid (natural, must wait for it to disperse) and the mechanical disadvantage of pucks that have not yet settled out towards the rotor where they belong.

By the way, does the idle of the car change in any way when you touch the brakes? Question because that might indicate a leak at the booster (it is pressurized via manifold pressure). If you have idle fluctuation then you may have a leak.

John
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Old 06-17-2003, 10:36 AM
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Thanks for the replies. Keep them coming.

Slider, I heard the opposite. I thought with foot on the brake, start engine, the pedal should depress... That's what's happening.

I guess I don't understand how a brake booster could affect where the pedal stops and applies the brakes adequately.

I will go back to it later today (tonight) and reset the "slop" in the pads. When I rebuilt the calipers the first time, this seemed to help. I have since rebuilt the calipers again... because of the WAY I rebuilt them.

BTW: The pads are old... 1 year or so.
The rotors look good. I hit them lightly with small disc sander just to make sure the glaze is off.

I noticed that all wheels and rotors appear to be equally hot after a little ride around the block with heavy (or atleast trying) braking.

I am too upset to continue working on it today.

Anyone else with a suggestion?
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Old 06-17-2003, 10:59 AM
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Nick,

Yep that's right, when you start the car with your foot on the brake pedal it should drop.

My moneys on what John says. I rebuilt all my calipers, and it took a few hundred miles to bed the new seals in. Try a spirited drive and get some serious heat into those brakes!

Good luck!

Cheers
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Old 06-17-2003, 11:48 AM
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Thanks for the info AirCE.

These brakes are too scary for a spirited drive. Maybe a casual Sunday drive with no traffic...

I drove a little around today. If I pump up the pedal atleast three times, I get pretty good (not great) brakes. But still, it only last that one time until I pump them up again.

I emailed Bob @ Pelicanparts. He suggests I STILL have air somewhere in the system. I went through 5 1/2 quarts of fluid now.

I will try two more quarts, then I think I will HAVE to take it to a Porsche Mechanic.

Anyone else concur or suggest more driving?

Could it be too much brake fluid on the pads?
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Old 06-17-2003, 08:19 PM
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Nick:

Here's one situation where time will heal all (well, that's my thinking anyway). Every time we bleed our brakes, we rustle up the fluid and introduce air - can't be helped.

Many posters at this 'board that follow up on their brake threads talk about how the soft pedal "fixed itself." I *think* what is going on is that the trapped air has moved through the system and vented to atmosphere. We all know about tapping the calipers to dislodge larger bubbles, but here I am referring to the microscopic air that pervades the system post-bleeding.

I would not bleed the system again. I would however take the advice I gave above about pre-loading the puck/pad/rotor side of things (what I think of as the mechanical side of this problem). The air is something else entirely and it simply takes time to get that out.

Let us know how it goes - I'd like to know if I am wrong. I also cannot comment on the new booster and hookups. If you were "bleeding" air through this side of things then all bets are off.

Best of luck,
John
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Old 06-18-2003, 07:46 AM
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Quote:
Originally posted by nhromyak

Could it be too much brake fluid on the pads?


I hope you don't have ANY fluid on your pads! If you do, that would explain the poor stopping power, not the mushy pedal. Even with a mushy pedal, the car should stop relatively well after "pushing through the mush". If your pads have any brake fluid on them replace them.
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Old 06-18-2003, 08:31 AM
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So if I had brake fluid on the pads (soaked really) and cleaned it with Brake Parts Cleaner they would still be bad???

Thanks for the info.

APPARENTLY I have been bleeding the system incorrectly according to the Bentley Manual .

The Bentley specifies the method for bleeding brakes with a pressure system. Everything is the same except the following ADDITIONS.

-- Attach line to bleed nipple and a waste container.
-- Have helper hold brake pedal down.
-- Open Bleeder Screw
-- Have helper slowly pump brake at least 12 times with bleeder screw open.
-- holding pedal down on last pump.
-- Close bleeder screw and release brake pedal.

Hopefully the above additions to my one-man crew of bleeding brakes will help me.

Previously, I have only been following the technical bulletin on this sight on how to pressure bleed the brakes. I had a helper help me with once for a "normal" pump and hold - open bleeder, close bleeder, release brake.

I may just change the pads out anyway...
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Old 06-18-2003, 08:46 AM
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Two ideas come to mind. Not to insult you, but are you sure you have the calipers on the correct side of the car? That is, with the bleed screws at the top of the caliper? I was brain-dead once & put the left caliper on the right side of the car before I realized what I was doing. That will definitely give you that spongy pedal.

Another thing that happened to me with another car, giving the same symptoms you describe, was a semi-clogged vacuum valve. This is the valve that takes vacuum from the engine & uses it in the brake booster. When my Alfa had this problem, it drove the shop nuts until the clogged vacuum valve was discovered.

HTH
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Old 06-18-2003, 11:06 AM
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Thanks for the reply, I did one caliper at a time, the bleeders are on the top of the caliper.

I don't get a solid pedal with the engine off, I guess I don't see how the booster could affect it.. could it???

I am expecting a rock solid pedal with the engine off. IS this not the case? ---Anyone---???
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Old 06-18-2003, 11:46 AM
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Tow it to a shop and have it looked at. You need a fresh set of eyes on it now...
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Old 06-18-2003, 12:20 PM
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I think you are brakes are normal. In my opinion that little bit of mush never goes away and after a hard day at the track it gets a little worse but the brakes still work fine.
Sometimes when I put new pads in the rear the pedal seems a little firmer but after driving hard it always goes back to that 1 inch of mush. I think that hard stop you feel in the pedal halfway down is the pressure-limiting valve for the rear brakes. I wouldn't worry about it and drive.

Tim
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Old 06-18-2003, 12:35 PM
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I agree with Tim. I had very hard brakes but as things progressed I lost that hard feeling. I have a bit of mush, but not as much as before all of the bits bedded in one to another.

Bring on the jokes folks!

John

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Old 06-18-2003, 12:37 PM
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