Reimu

With the car off it gets hard, with it running it stays soft no matter how much I pump. The MC acts the exact way the old one did.


Tonight I compressed the pistons and fumbled around with the calipers and bled again. No change.

Reimu

Would that really make it feel mushy? If the pads weren't bedded in it seems like that would feel more like bad braking with a properly stiff pedal.

I've considered buying a set of pads just to try it out but I'd rather not fall down the slippery slope of throwing money at something praying it works.

morghen

how much did you drive it?
i took out the pads and cleaned the calipers...after that, i bled and bled and bled the system...with the engine on i could not get a solid pedal....so i said..the hell with it and i'll see whats what later...drove it a few days and as i put more miles on it the pads re-beded, the brake performance improved significally and pedal became much better.

Paulyy

make sure all the pistons move equally in the callipers. a frozen piston will make you brake less.

Lilja

Binding brakepads will also cause your brakes to feel strange. Its very common on the brembo 4 piston calipers that they corrode under the little steelslide where the pads sits causing them to bind the pads up.
Brakelines can also have a massive effect on how the brakepedal feels, they can sometime expand when youre pressing the brakepedal which makes it feel like theres air in the system.

I have a question on my own thou. I have a 85 944 and a 91 S2. I have completely stock brakes on the 85, on the S2 I have 928 GTS front brakes and steel lines all round. However the 85 brakes as soon as I touch the pedal but there is a considerable amount of play on the S2. It doesnt feel like it has air it just feels like an old Chevy when pushing the brakes, it stops but its not even remotely as exact in the pedalfeel as the old 85. Shouldnt it be the other way around?

CliveB

I really hope you find a cure for this. I have suffered for years, changed master, steel braided brake lines etc. Do you have a creaking sound from the calipers when car is not moving and pedal pressed hard?

Reimu

I do hear a screech from the other calipers when I pump to bleed sometimes, I figured it was the calipers grabbing the rotors. Did you ever change pads and see if it helped the problem?

Thats kind of my last hope before giving up and holding off on the problem until I go with turbo brakes or something.

Reimu

As an update
I replaced all pads with used throwaways and bench bled the master again at all ports, followed by bleeding the calipers. No change.

However I have noticed that while being really hard on the brakes and bedding them in I feel the pedal start to firm up a bit, or at least I think I do but it resoftens quickly. And no these aren't race pads that have to be cooking.

When changing my rear pads I noticed the passenger side ones had wore at a pretty significant slope. What do you think of that?

mytrplseven

IMHO, I've done this dance and I replaced the rotors, pads and DOT approved stainless brake lines. Then, using the BLUE brake fluid so I knew when the old was totally bled out, I used the power bleeder. Just for the sake of comment, per recommended procedure, went with Rt rear first, Lft Rear second, Right front third and then Drivers side front last. After I saw Blue in all bleeder lines, took her out for a break in drive and Shazam, she breaks hard and true now. I suspect your old rubber lines are swelling with pressure and need to be replaced with DOT approved stainless braided lines. It's easy and plan on not trying to anchor them to the little notch in the strut. They're too narrow. Just make sure that they don't catch on anything. They can be twisted enough to accomplish that.

Gawernator

I was also going to say try stainless steel braided DOT lines. I just put them in along with new pads/rotors/fluids/rebuilt calipers and the pedal is nice. Car stops quickly.

Lilja

I have stainless steel braided DOT lines from Lindsey racing but my problem percists after many many bleedtries. Theres absolutely no confidence in the pedal. I also have new calipers in the front and new rotors and pads. The rear calipers are good.

Reimu

Ok here's a new one

I put a broomstick on the brake pedal and put a mark on the reservoir where the fluid line is last night. When I went to the car today I noticed the pedal seemed a lot harder than it was the night before and the stick was really pushing into my seat.

I drove around and the pedal was a lot stiffer and although it wasn't rock hard it was still a MASSIVE improvement.

Sadly the pedal returned to its former mush before I made it back home after a 5 mile trip.

Not really sure how to call this one

ClassJ

Couple things to check and tips for stubborn systems. I went through this and it turned out to be a combo of a bad fluid choice (DOT 5), and pads that would not bed for anything.

-When you re-bleed do you get air? You should be using either clear tubing so you can see the bubbles or some other indicator so you can tell if there is air beyond the first pump.

-What brake fluid are you using? Different brake fluid brands have different compressibility believe it or not. If you are using silicone dot 5 fluid, thats your problem, PM me and I will tell you how I flushed the crap out of my system. Use a good DOT 4 fluid, castrol LMA at the worst. ATE or better is what I prefer. Don't keep the cans in your car, use new un-opened product. Let is sit overnight on the shelf before using it. We want all the entrapped air to float out of it.

-I had issues with a set of front pads bedding once. Turned out they were packaged wrong from the vendor. I threw in a new set of pads and new rotors and things started getting back to normal

-Try doing a two man bleed. Get a helper to sit in the car and work the pedal. Pedal movement should be slow and take at least 2 to 3 seconds to lift from the floor, pause a few seconds to allow the system to fill, then slowly back down for another push. Brake fluid can be agitated and aerated, especially on the 944 I found, makes it impossible to get the air out.

-After you bleed the car, wait a few hours, or overnight, and do it again. The second bleed will force out any entrapped air.

-On some cars, you can suck air back in through worn caliper seals. When you lift up on the pedal, a slight vac is formed in the system which normally helps pull the pistons back in addition to the way the calipers are built. It is possible that you could be drawing a little air in. This or a bound caliper could cause issues

Tay-Tay

I've been having similar issues for years. New master, pads, rotors, a few gallons of ATE blue/gold (w/ power bleeder) over the years, and braided lines. The braided lines got me to the point I could occasionally get a wheel to lock with the pedal to the floor, so I believe these or at least new OEM lines will help you.

I DE the car and Hawk Blue and HT10 are great, and I can get them to lock. It seems to me, for the street, Porsche brakes (metal master pads) should lock up if I try to make them.

I'll be following this for other ideas.

Taylor
87 951

Reimu

Guess I'll return to this thread since I went a little overboard.

I replaced my old calipers with remanufactured lexus ls430 brakes (slightly bigger than big reds), and the rears with 951 rear calipers in good condition, r4s pads. Replaced all the lines with stainless steel and bled with ate.

Pedal would travel an inch and a half or so before getting solid. If I pushed down on it the rears would lock, which is something at least. Figured the calipers were too big for the master so I bought an older bmw master cylinder with a 25mm bore front and rear; required me to modify the lines a bit as there is only one port for the front/rear. Went on with a wilwood adjustable bias valve.

There is virtually no change. If I turn the bias valve all the way down the rears won't lock but neither will the fronts. Is it possible that the rear brake pistons are too small in comparison to the 42x42 lexus calipers and I can't get adequate fluid pressure to them because the rears pressurize so quickly?