Problem bleeding brakes - any pointers out there??
 

Greetings to all! This is my standard operating procedure - Saturday night and I'm stuck on another DIY project. We've all been there before, right?

I rebuilt my front calipers this weekend and replaced the rotors and pads. Now when I bleed the front brakes, I can't get rid of the mushy pedal feel. I've pumped each side probably a dozen times, tapped the calipers with rubber mallet, etc. But I still have a mushy pedal.

Here's my question: Is it possible that I need to bleed the rear calipers as well even though I didn't even touch my rear brakes? Could air possibly have worked itsway into those lines as well? Sounds unlikely to me, but I figured I should ask.

FYI, I also had the brake pedal jimmied down with a 2x4 while I did my work. Any pointers for getting my firm pedal back? Thanks to all

ok....here is how I was instructed.

Bleed all 4.

Start in the back (left)....then (right)
Front (Left)...then (right).

Worked great for me and the pedal feel was perfect.

if H.D.'s routine doesn't do it,

then try re-installing the front pads with the pistons over extended an itty bitty bit.. so you gotta jam the pads in super tight with a tap tap tap of a hammer. I shave the pad leading edge to a bit at an angle ..............Ron

Make sure the bleeder valves are on top. Don't ask...

Start with the wheel farthest away from the master cylinder then work your way closer. I was always told the order should be RR, LR, RF, then LF. I've always done it this way and nailed it the first time around.

I think a combination of power bleeding and pedal bleeding gets the last of the air. No proof on this. Just therory. When pedal bleeding with two people, ask the person in the car to push hard and open the bleeder valve slowly and make sure you close it before they reach full pedal travel. The additional system pressure seems to dislodge trapped air. Again, just therory.

I usually drive it around the block and then quick re-bleed.. about 1/2 the times I get an isolated bubble..

but the piston seals may be retracting the pistons in this case if he didn't jam the pads in. if you eyeball the seal, you can see how this can happen.................Ron

Ckelly is right you need to bleed the cylinder furthest from the master cylinder. So if your car is a LHD (Left Hand Drive) you need to do the rr brake first, than the lr brake, rf and finally lf.

If you are using another person to pump the brake have that person pump the brake three time and hold it the pedal, slowly open the bleed nipple and the pedal will go down when the pedal has bottom the brake person pumping the brake should tell the person opening the nipple. The person opening the nipple should than tighten the nipple and once the nipple is tight tell the person holding the brake pedal to release the pedal. Do a couple of time and the brake should be firm.

I had to take mine for a few rides to break the air in the caliper loose. Then it required rapid multiple bleeding on each corner so the air doesn't have time to work its way back up. We did it the old fashioned way with a helper, no fancy tools. Just keep the faith and you'll get it.

IPurchased a power bleeder and if I had to do over again I would not have bought it unless you plan on doing a lot of brake bleeding. I have found the best way is to submerge your bleeder hose in a jar of brake fluid at all times while pumping the brake pedal, you can see all the air come out and the line being submerged in the fluid insures no air will get back in the line. If you do use a pressure bleeder make sure you clamp of the line by the reservoir or you will have a nice puddle of expensive blue on your floor.
bk

If I had a buck for every "don't ask" moment in my life...

Oh wait, we're talking about working on cars.

Also, you will have mushy brakes for a while no matter how well you bleed the brakes, until new pads get themselves bedded-in.

I went through a big long scary bleeding session with my Carrera brakes.

I replaced the M/C and rebuilt the calipers. It turns out I didn't eed to rebuild the calipers.

But, I went through 12 quarts of brake fluid, until I was able to completely purge the air out of my brake system.

I don't think you should ever have a mushy pedal. After I tried the "drive it a while -they will come back" suggestion. I still had a mushy pedal.

BUT you will have lesser performing brakes until the brake-pads bed-in. But you should still have a hard pedal!

I never actually FOUND air in the system - but somewhere I did bleed it out - or when I switched out my bleeder nipples all was right.

After following the normal, and usual bleeding instructions for both pressurized and conventional bleeding - and using over 8 quarts of fluid with minimal results - I followed the bentley manual for bleeding with a pressure system (e.g. E-Z Bleeder by Motive).

Hook up Bleeder with two quarts of fluid in it.
Pressurize it up to 20 PSI.

OPEN BLEEDER NIPPLE (with bleeder nipple connected to a hose to a suitable container).
PUMP the pedal ATLEAST twelve times. (I did it fifteen times).
CLOSE BLEEDER NIPPLE.

Move to the next nipple.

I found pumping with the pressure system, took a QUART of fluid for EACH CALIPER!

GOOD LUCK!

There is something horribly wrong if it takes 12 qts. of brake fluid to bleed your brakes. What do you think went differently w/ the 12th quart, (as opposed to the first 11)? I replaced all of my soft brake lines on my car as soon as I bought it, (switched to stainless steel), and then bled the brakes w/ I think less than 1 additional quart, (over the system capacity, which was completely emptied). Rock hard pedal right off the bat.

Just lucky? I don't know. I have definitely experienced systems that were stubborn to bleed, my 911 wasn't, but in any case there are a few things to check before you dump gallons of brake fluid into it. I own some kind of power bleeder, never have used it, prefer the helper method or Tyson's one person method. Conventional wisdom is to start at furthest wheel from MC, but if system is empty it is very helpful to quickly bleed fronts first in order to have sufficient pressure to the rears to push the air out of the longer lines. THEN do the rears and double back to the fronts as a finish. You should be getting a strong, even stream out of each bleeder, (not one wheel different from others), if not there is a problem. You need to investigate; is it a damaged or plugged bleeder screw? Squished brake line? If the pipes are clean, (sorry), :D , air will be easily pushed out by extreme hydraulic pressure.

This is pretty general info, as for your car Rob, definitely bleed the entire system, it doesn't take long. Sometimes you need to bleed upstream of the wheels if system was completely emptied, ie. bleed @ MC or proportioning valve first, you always move downstream, hence my advice about doing fronts first. Good luck! :cool:

12 qts of super blue @ $12.99 WOW!!!!!!

Thanks for all of the helpful suggestions. I just bled all 4 corners and the pedal firmed up a bit. Still not firm enough, but I did replace the brake pads and front rotors as well, so maybe everything simply needs to bed in a bit.

So the game plan is that I will load my 2 year old and 4 year old into the car tonight to take about 10 slow laps around my block while repeatedly pumping the pedal. The kids will think it is great and hopefully I will get rid of the last gremlins.

Before anybody flames me for taking my kiddies with me, I live in a gated community with no traffic and I will be driving less than 15 mph! :) :)

Extra space between the pad and rotor should produce a longer pedal. However, if there's no air in the system, the eventual pedal should be hard. Mushy pedal = air.

One quart per caliper? 4 quarts per caliper? At this rate, I don't see the advantage in pressure bleeding. I can gravity bleed a dry system with less than 1 quart of brake fluid .... even very expensive brake fluid.

Sherwood Lee
http://members.rennlist.org/911pcars

Yah, I ditched the super blue after the second quart with no improvement. :(

I am running the cheap stuff in it now. It's fine for street.

If you want to bed in the pad correctly you need to get them hot by doing a couple of hard stop and then let the car roll to a stop without using the brake. The run out from the rotor will push the pads away from the rotor so that they can cool down without touching the rotor.

With the brake problems that I have had at the track, I consider myself a TRUE professional in the brake department.

Clamp the overflow

No you don't need one liter of fluid for each corner. with a power bleeder you need to bleed each caliper bleed screw for about 10 seconds

Always start w/the furthest caliper as ckelly and ruf-porsche have suggested, RR, LR, RF (outside then inside) and LF (outside then inside)

Tap each caliper with a rubber mallet as you are bleeding to get all of the air bubbles out

Make sure that you fully tighten each bleed screw

If this doesn't give you a firm pedal, you probably have a master cylinder issue in which case you will have to drain all of the fluid you just put in and replace the master.

Prior to that however, make sure that you don't have a leaking caliper. You may see paint peeling on the caliper or fluid on your wheels. Put the car back up on stands and depress the brake pedal while someone CAREFULLY checks all lines and calipers.

New pads and rotors will shorten the pedal but not necessarily give you a firm and consistent pedal.

It could be that the pistons on the calipers are not the proper distance from the pads. If they are not set to the back of the pad it would take a couple pumps to get then to the point where they actually move the pads to contact the rotor. When you let off the brake there is enough suction to pull the pistons away from the pads again. There are a few things you can do.

You can take the wheel off, pull the pads out and put something ( I use a small block of wood) that is a little thinner than the pads and press the brake pedal. You need the block so the pistons don't come out of the calipers. Also try different size blocks until you can barely insert the pads. If you go to narrow and can't get the pads in you will need to force the pistons back into the caliper a little. ( I have used a c-clamp). Then check the fluid and move on to the next wheel. This procedure solved my problem when I did my brake rebuild last year.

The other way I was told to fix it was to just drive carefully and they would slowly adjust themselves. I wasn't comfortable with the spongy brakes so I opted for the first solution.

Good luck.

Of course this is provided that you think you have removed all the air from the system as the others have stated.

------------------
Gunter
'82 SC Targa

It could also be that your other car is a 993TT - the brakes in that car will make just about any other brakes feel a bit off.

ZCAT, That is true, those 993tt's stop just short of doing reverse wheelies, :eek: , but Rob has had enough early cars to know what to expect, also. :cool:

I went thru this (multiple quarts of fluid) with a buddys 71 911T afetr we installed SS lines. We finally traced it to a MC issue, I believe there have been a number of threads on this but if I recall it is an issue of the piston in the MC going to far and a seal getting deformed/?reversed?? Somebody with more technological expewrtise chime in.

Richard, that is certainly one possible explanation, and these discussions apply to any car, nothing at all unique about the 911's brake system.

My point before was that if it takes 12 quarts :eek: of brake fluid to bleed a car, it might as well take 20 gallons. Something is not right, the time to investigate is when the first quart doesn't do it. :cool:

Exactly Denis..but then again we wouldn't be male if we didn't beleiev we could get ourselves "unlost" by just driving on a bit...or trying just one more bleed sequence........ I think it only took Tom and I 4 qts to realize our issue was elsewhere...but we have both been married awhile.....