Too much free play in brakes

[e46m306]

Been struggling with too much free play and loss of confidence in brakes lately. I have ST40 Stoptech brakes which used to make the car stop and nearly toss you thru the windshield. Now the pedal depresses much further and I keep realizing on the track in close conditions that I'm pumping the brakes. I bled them multiple times and then replaced the master cylinder a day ago. Phew that was fun. Bled them after the MC change and have a foxwell 530 which i used to bleed the ABS. But after all that effort they are still not confidence inspiring. I don't think there is an adjustment for free play on the pedal. Could there be some issue with the pressure sensors? I don't have any error codes for the ABS/DSC either.

Probably need to mention I use PFC11 brake pads and they are fairly new.

I pasted the manual troubleshooting suggestions. Kinda small though but the suggestions are MC or electronics or bleeding

brake_diag.jpg

[eacmen]

Been struggling with too much free play and loss of confidence in brakes lately. I have ST40 Stoptech brakes which used to make the car stop and nearly toss you thru the windshield. Now the pedal depresses much further and I keep realizing on the track in close conditions that I'm pumping the brakes. I bled them multiple times and then replaced the master cylinder a day ago. Phew that was fun. Bled them after the MC change and have a foxwell 530 which i used to bleed the ABS. But after all that effort they are still not confidence inspiring. I don't think there is an adjustment for free play on the pedal. Could there be some issue with the pressure sensors? I don't have any error codes for the ABS/DSC either.

Probably need to mention I use PFC11 brake pads and they are fairly new.

I pasted the manual troubleshooting suggestions. Kinda small though but the suggestions are MC or electronics or bleeding

brake_diag.jpg

Honestly, keep on bleeding them. I have used a Motive bleeder repeatedly and it never got the air out. I switched over to a one man bleed bottle with the check valve and it worked much better.

And the two man bleed is probably still the best most reliable method.

I’ve never tried gravity bleeding but have heard good things.

I bought a few liters of inexpensive brake fluid to get this done. Once the air was out, I flushed it with the expensive stuff.

[e46m306]

One other kind of odd item is that the moment i turn the key to the ON position, I start to hear the hydraulic/control unit clicking. I can't remember if this was evident before.
I've bled them so many times but I'll give it another try. I just never see any air bubbles coming thru the bleeder line. I may try the cheaper fluid routine cause I can't see continuing to blow thru expensive race fluid like I'm doing any more.

[eacmen]

One other kind of odd item is that the moment i turn the key to the ON position, I start to hear the hydraulic/control unit clicking. I can't remember if this was evident before.
I've bled them so many times but I'll give it another try. I just never see any air bubbles coming thru the bleeder line. I may try the cheaper fluid routine cause I can't see continuing to blow thru expensive race fluid like I'm doing any more.

I hear you. I’ve battled the same thing. Gravity bleed might be in order. Get four drip pans and crack the bleeders and crack open a beer and let it do its thing, just don’t let the MC run dry!

Wailing on the calipers with a dead blow helps as well.

Also if you havent driven the car hard in the brakes yet(bed in) might want to do that before chasing this problem. I’ve seen the brakes firm up after a good bed in.

[slides]

When I replaced my MC a few months back I couldn't get the peddle to firm up. After reading up you need to bleed the ABS unit as well. Turn the key ON and get to bleeding.

I also used around 100oz of cheap brake fluid during the whole operations (learning experience) and then flushed with motul 660 in the end.

[e46m306]

I did bleed the ABS with foxwell 530.
One thing i notice the next day is that there is a bit of brake fluid around each of the bleeder screws seat. I cleaned them all with brake cleaner so that has to be new brake fluid. It's not very much and its on every screw so it has me wondering if its just some residue that's meaningless. I torqued all the screws to 112in/lbs just to make sure.
20210225_165012.jpg

[eacmen]

I did bleed the ABS with foxwell 530.
One thing i notice the next day is that there is a bit of brake fluid around each of the bleeder screws seat. I cleaned them all with brake cleaner so that has to be new brake fluid. It's not very much and its on every screw so it has me wondering if its just some residue that's meaningless. I torqued all the screws to 112in/lbs just to make sure.
20210225_165012.jpg

Brake fluid coming from bleeders is no bueno.

Remove the bleeders. Clean the seats and the bleeder mating surface. Then re-bleed.

On the stock brakes I just replace the bleeders with new ones.

The torque spec is basically just a guideline. All you need to do is bottom out the bleeder into the seat to create a good seal. The threads are not used to create a seal, its the seat. Remember you’re seeing up to 1500 psi in the braking system, it needs a true seal. Do not use teflon tape or any other thread sealant it will give you a false sense of security.

If its not sealing and the bleeder is snug then there must be debris or corrosion in there.

I’ve also taken old bleed screws, grinded off the threads, then used some light abrasive (valve lapping compound works). To clean the seats with some success.

[e46m306]

Raising in the desert does seem to toss up dirt in every nook and cranny of the car so this sounds plausible that there's dirt in the seats.
Thanks I'll have a look at that although with 8 bleeders it will take some time.
I measured the play before the brakes engage and its probably about 2.5" which I'm fairly sure is more than it used to be. That's with the engine on.

[eacmen]

Raising in the desert does seem to toss up dirt in every nook and cranny of the car so this sounds plausible that there's dirt in the seats.
Thanks I'll have a look at that although with 8 bleeders it will take some time.
I measured the play before the brakes engage and its probably about 2.5" which I'm fairly sure is more than it used to be. That's with the engine on.

I usually measure pedal travel with the engine off and the brake booster empty of vacuum.

If you have fluid leaking you should be able to apply constant pressure to the pedal and feel the pedal sink.

[dalecan]

Just a thought: Are the rubber bake lines worn and expanding? It might be worth putting stainless lines in.

[e46m306]

They are SS on all 4 corners. I'm going to try to bleed only the master cylinder by opening brake lines there