I have been having problems with my brakes recently and I was wondering if anybody has any ideas on what could be wrong. They symptoms are a soft pedal at the top of the stroke, followed by very little stopping force lower in the stroke.
Here is the background info:

Thursday night: Bled brakes in preperation for FATT. Sucked air into the master cylinder three times
re-bled that night. A LOT of air in the lines. duh.

Friday: re-bled again before going out on track. Brakes felt fine but didnt push them as hard as I would have normally. (on used up rotors and low XP pads)

Sunday: Installed stainless steel brake lines (re-use union bolt), new rotors and 1/2 used Ultimates. previous rotors and pads (XP) were done. Bleed brakes, a lot of air in the lines. Thought this was normal due to new lines.

Monday: car wont stop. drive to work is scary. A lot of pedal stroke and very little braking. Pedal is at the floor to get any kind of braking force.

Monday night swapped out the original union bolt (thats what the service manual calls it- the hollow bolt with the hole in it that attaches the brake line to the caliper) with one that came with the brake lines. swap front rotors (on backwards whoops). Bleed again. A lot of air in lines again (Matt described it as the brake lines 'farting') We bleed until nothing but nice new bubbleless fluid. Take it out for a spin and do some hard stops to season/bed the rotors and get the shiny silver paint (or whatever) off of them.

result: brakes are better than monday, but still dont stop real well. There is dead pedal stroke at the top, and when the pads do contact the rotors there just isnt any bite. and the ultimates should bite pretty hard.

My current plans are to put clean towels under each wheel and pump the brakes to see if there are any leaks in the lines. That is my best guess right now.
Also the possibility of air getting trapped in the ABS system has crossed my mind, although subaru uses an 'open' ABS system, and the service manual says that normal bleed procedure is all that is necessary.
If that doesnt work than the stock rubber lines are going back in, and take it from there.

any ideas of what could be wrong? Am I just a dumbass or what?
Ive got 3 days at VIR this weekend and I need to get this problem solved asap.

thanks,
Evan
-(likes parenthesis() )

 

For some reason my brakes were also soft for a while after installing braided lines. I seem to remember others talking about this too. I don't know if it's a function of the new lines, or just that you eventually get the last remaining bubbles out of the system after a few additional bleeds.

 

And we're talking A LOT of air, I mean at least 4 or 5 full pumps of nothing but farting bubbles from each caliper.

I might add that Evan, being very concerned didn't just have me close the speed bleeders as soon as we started seeing the bubbless blue. He gave at least 3 extra pumps on each one before I closed the bleeder.

Then once the initial bleed was done we went around for a couple more pumps on each caliper to ensure there was no air trapped in the lines somewhere.

YES!!

 

There is no mechanical reason that you should have a softer pedal w/SS lines than without. Check your owner's manual to see if there are any specific recommendations for "bench bleeding" a new master cylinder - that is where you are starting (effectively) when you suck air. I don't know about your system but there might also be particulars associated with any brake balance control valves, if present.

I have heard of successes "reverse bleeding" air out of the top (MC end) of pesky systems, using a large syringe (vet supply store nearby? ) and a really tight-fitting tube on the caliper bleed valves, shoving fluid backwards through the system, watching the reservior for bubbles and/or overflow.

I am still guessing but you might have over-travelled your MC, trying to brake with lots of bubbles in the system - again, I don't know from Subarus but have heard of seals being damaged from this on other car models.

Good luck!

Kirk

 

Are you positive the pads are seated int eh caliper properly. I had a crooked pad once that made the pedal feel like crap - the pad was being flexed instead of pressed onto the rotor. Boy did I feel like a jackass when i figured it out.

 

Some cars need to have the ignition energized when bleeding to get all the air out. VW/Audi's, F-Body GM cars, and many others. You might try that if you haven't been doing it already.

Also, you haven't mentioned (or maybe I didn't read) how you were bleeding the brakes (traditional, speed bleeders, vacuum pump, etc.). For what changes, you've made you shouldn't be having this much trouble. It might be a problem with the bleeding (like a leaky speed bleeder sucking in air).

 

sounds like you just keep getting air in the system and need to make sure youre not introducing more air when youre bleeding the system. just bleed it and stop getting any more air in the system by keeping an eye on the MC. it helps to have a really patient friend who's willing to give his leg a work out.

no, definately on hondas the brake booster does not need to be utilized when bleeding the brakes. i dont see why it would be necessary on other cars either since the brake booster doesnt come in contact with brake fluid, but i only know hondas.

 

I checked the factory service manual, and there is no seperate procedure for bleeding a new master cylinder, a standard bleed is what it says.


ugh. Any idea how I would check that?

 

I am using speedbleeders, they are new only a couple months old. as far as I can tell they work properly, althought that certainly is a possibility

 

I know somebody here was having brake problems similar to your's, and he also had Speed Bleeders. I don't remember hearing if they were the culprit, though.

maxQ??

 

I haven't figured it out... HOWEVER, after the "My brakes are mushy!!" thread that Mr. SlowSER is aluding to, I bled all four of my brakes with the help of a certain WRX wagon driver using the traditional "brake down, brake up" method and the pedal is very good.

Any time I've bled the brakes by myself using the speedbleeders... I've had a poor pedal. YMMV.

Andy - who's rear speedbleeders are coming off next brake bleed.

 

I still have to think that it's a bleeding issue. Everything seems to have worked on Friday. The problem I see is that every time you tried to fix a problem your first step was to crack open the braking system, forcing you to re-bleed everything.

Checking for leaks sounds like a good start. I would also suggest opening the speedbleeders just enough to get fluid to come out. Opening them too much seems to have contributed to some of my problems. Did you happen to notice if your fluid level dropped any Monday?

I've decided to remove my speedbleeders at some point in the near future. I haven't gotten around to buying more stock screws though. I've recently started using an air-powered vacuum pump at home and it's worlds above the speedbleeders.

I also recently aquired a brake bleeder bottle with a check valve in it. I'm going to try it out at VIR if I need to bleed there. Hopefully it'll help the situation some.

 

I noticed monday night that the fluid level had dropped a little. What does that mean?

 

FWIW i dont like the vacuum bleeders. i use a mityvac hand pump and it sucks a lot of air thru the threads and back into the nipple or around nipple into the tube. You cant get a good measure of how much air you are sucking out of the lines since you are constantly sucking air out that did not originally come from within the brake system. but then again, maybe this tool does things better. still, nothing beats the simple way of doing it with 2 ppl.

 

Check to see if your pads are in the retaining clips correctly, like Crack Monkey said.

I had a MC go out on me after at track day. Decided to put on SS lines and new pads at the same time. I bled the mother forever using power bleeder & standard pump and release. Everytime I would check the pedal it would be "mushy". Brakes worked and pedal didn't go to the floor, but pedal travel was excessive.

After about a week, the pedal stiffened up. Was swapping back to my track day pads and when I pulled the left front caliper, the inner pad was bent!

The Bendix pads I put in didn't fit very well and when I lowered the caliper back down they must have slipped out of the retaining clip.

The rear pads could "flex" as well if the inner pad tab isn't aligned in the piston cutout.

Just some things to check that may save you the hair pulling and embarrasment I experienced!!

 

Uh-oh. I need to back up a few steps...

SpeedBleeders schmeedbleeders - or something to that effect. In my book, the thing is either open or closed, depending on which way the guy/gal with the wrench has it turned. Anything else is a trap. Ditto vacuum bleeders, that pull air in through the threads around the bleed screw.

The only brake bleeding tool (besides a tight hose submerged in a plastic bottle of fluid with a hook on it) worth using is the pressure type that snaps over the MC reservoir (a la Snap-on's version).

Regardless of whether the fluid is pushed through by air pressure or someone's foot, DO wrap all of the bleed screw threads with teflon tape (careful to keep it off of the very end and out of the caliper) to avoid the air leakage problem.

Also, make SURE that you don't over-tighten them! Particularly with some caliper castings it seems, you can groove the seat and they will quit sealing, even if they are just a little too tight.

I am old school (really old) and more than a little **** about this stuff but I deburr the edges of brake pad backing plates, to help prevent them from hanging. I also actually put those little rubber caps on the bleed valves

Kirk

 

you sure about the teflon? i just consider introducing a foreign material into the brake system a bad thing. also, teflon does have its own maximum high temp. i do know mightyvac actually recommends putting teflon around the bleeder screw to prevent pulling air thru, but i dont buy that kludge method, and im not comfortable with bandaids around my brakes.

 

I fought with a mushy pedal for 6 months until I figured out that I hadn't lined up the X groove on the rear pistons with the studs on the back of the brake pads.

It's worth a check. This caused mucho pedal travel.

 

dammit evan... do i need to go back over there and work on your car for you? Oh and those things are called banjo bolts. Where they came from doesnt matter.

This is one reason i did *not* buy speed bleeders. It introduces a varible into the braking system and its something i just dont want. Still searching for a better solution to the pressure bottle for a bleeder system. Back to home depot and chit at some point this weekend. However, my brakes are fine.

Since you're having issues with the brakes this is what you'll need to do now. I assumed that since you had speedbleeders you wouldnt need to do this. Put car on jackstands and get some buckets/containers of some sort (4 of them). Remove banjo bolts on all 4 brake lines and drop them down into the containers and gravity bleed all 4 brake lines. Make sure MC remains full. Re-attach all 4 lines. Put a very tight fitting peice of tubing on the speedbleeder, and crank it open 1/8-1/4 turn and wail on it 10 times. Do each line in order (RR, LR, RF, LF) and then see how it feels. You have air in the lines somewhere. This has always worked when i've done brake lines on other cars.

I stopped using speedbleeders and even a 2nd person to do the job. I just attach the line and drop it into my container, while wrapping a 'loop' in the line and securing it. Wail on pedal 10-15 times. Close up bleed screw, i'm done.

RJ

 

I worry about this, too. Teflon melts at 550° F... Surely, the calipers get hotter than that?

 

maybe fine air bubbles making the path back up to the master cylinder?

 

i've had good luck with a gravity bleed. no chance of negative pressure in the system with a gravity feed, unlike the pump method.

nate

 

Hi,
It sounds like you have air in the lines from when you let air in the mastercylinder. It can take an incredible amount of bleeding to get all of the air out. Anyone who has had to bench bleed can tell you.

Bleeding tips:
1) Make sure you keep moving around all four corners of the car. Don't just bleed one corner forever. Air gets hung up at the prop valve, etc.

2) Don't trust the speedbleeders on a car that is tracked. I have had 5 out of 6 fail and they leaked around the thread as well. Bleed them traditionally if you have to. Open / close, repeat.

3) Use a pressure bleeder (like Motive) if you can. I will be bringing mine to VIR if you want to borrow it. Big green truck w/black EG hatch - license "All Motr".

Pedal should be firmer with SS lines than without. That's the whole idea!

-Phillip

 

I've used it on everything from IT cars to sports racers and formula cars with "real" racing brakes, without apparent problems. I do keep the wrap up at the hex end of the bleeder and pay attention to both condition and locatin of the wrap...

K

 

Thanks for the tips everyone!

Last night I bled 2 bottles of ATE through the system. (That makes 9 bottles of ATE fluid in 1 week) I took everyones advice and it seems to have helped.
also installed some new XP pads.

Pedal feel seems to be much improved, although still a little dead area at the top.
possibly the new full thickness pad has helped things also.

Philip I would like to try out your motive powerbleeder at VIR if you dont mind. I have heard it wont fit on my car but I want to see for myself.
I will be in the blue subaru with gold wheels and a w1nG big enough for a small family to live under.

Evan