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Soft Spongy Brake Pedal After Installing Soft Lines


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sdsusnowboards
Novice

Jul 30, 2022, 5:02 PM

Post #1 of 10 (695 views)
  post locked   Soft Spongy Brake Pedal After Installing Soft Lines  

2003 Toyota MR2 Spyder with 135k miles.

I changed out all the soft brake lines with aftermarket stainless braided lines. No leaks at either end of the soft lines. I bled each corner using the two-person brake pedal method and ended up with a soft spongy brake pedal, ABS doesn't work correctly, and the car pulls to one side under a quick jab of the brake.
I bench bled the master cylinder and bled everything again, using a Motiv power bleeder this time, running about a quart through in total. Same result.

No leaking around the master cylinder.

I've done a bunch of brake jobs and have never had a problem. Any idea what could be going on here?
The only diagnostic thing I've done is hold the brake pedal down to see if I lose pressure, to test for an internal leak of the master cylinder. Pressure remained constant.


Hammer Time
Ultimate Carjunky / Moderator
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Jul 30, 2022, 5:22 PM

Post #2 of 10 (692 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

You either have a bad brake line that is stretching or there is still air in the system. You might look into having it pressure bled.

If you removed the caliper for any reason you need to check to see if any brake pads got dislodged from their seat. If so don't re-use the pads, they will be distorted.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Double J
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Jul 30, 2022, 6:00 PM

Post #3 of 10 (685 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

What was the reason for replacing the hoses in the first place?
Why the braided ones? Just curious.

Did you use new copper crush washers during the install?

If you hold firmly down on the brake pedal , can you (or a helper) turn any of the wheels by hand? Especially the one opposite of the side it pulls to


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 30, 2022, 6:49 PM

Post #4 of 10 (672 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

Are those lines DOT rated or just for looks by anyone? Stuff matters now the car pulls with braking. Did it before? Did you save OE ones?

Did you twist them up, same length as OE or let a caliper drop with them attached - not a good thing.

If this all started with this and properly bled I'd just go OE ones save this dangerous grief if really soft they'd bulge at a spot seen with helper pushing pedal.

Back this up a second. If one did that + not the other any two on same would behave the same. Those banjo bolts may be the issue, were they checked?

T

T



Hammer Time
Ultimate Carjunky / Moderator
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Jul 30, 2022, 7:17 PM

Post #5 of 10 (659 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

I deleted your two responses as they were nothing but quotes of the previous response.

Please do not use the "quote' or "reply to" as they serve no purpose. We all see every response.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



sdsusnowboards
Novice

Jul 31, 2022, 6:35 AM

Post #6 of 10 (628 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

@HammerI did note that the rear pads were seated properly an appeared in good health Before installing the new stainless braided lines. At this point there shouldn't be any part of the brake system that could expand. Everything from the master cylinder to the wheel well is a hard line, and the flexible line is now a stainless braided hose.

I did use a Motiv pressure bleeder on my second go around.
Your deduction is valuable. I suspect air in the ABS module could be at issue, because I've never let lines upstream of that go dry before as I have here with the removal of the master cylinder to bench bleed. I hear anecdotally that the ABS module can be difficult to bleed. I also hear anecdotally, and that a pressure bleeder should have taken care of that for me.

@ Double JThe lines were replaced in order to achieve consistent brake performance in racing conditions. Braided lines were chosen to resist expansion when things get hot. In addition, with the age and mileage of the car, it seems prudent to replace safety components made of rubber.

The lines came with new copper washers which I used.

I will test the brakes in the manner you suggest and report back.
@Tom GreenleafI doubt these lines are dot approved. They are advertised as "DOT-type."

The lines I installed have not been twisted and have not held a falling caliper. They are the same length as the OE lines they replaced.

The lines came with banjo bolts, which I used. I superficially inspected them, but I didn't check for obstructions.


Hammer Time
Ultimate Carjunky / Moderator
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Jul 31, 2022, 6:40 AM

Post #7 of 10 (626 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

This is most likely a diagonal brake system and you still have air in one side.

Normally you could isolate the issue by pinching off individual flex hoses but that may not be possible with yours now.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 31, 2022, 8:55 AM

Post #8 of 10 (615 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

Suggestion: Put the original lines back on, if problem is gone then go get new ones and forget the stainless steel wrap IMO for looks real brake flex hose should be fine for realistic use on roads heat wise.

Agree that about 20 years old they should be new, most would wait for a failure frequently one will lock a wheel make it unable to return fluid.

Few would bulge I may have seen one over lots of years - perhaps just chance.

New doesn't mean making them worked out OE or these.

I thought I asked if the problem began just doing this? If so the hoses are the problem or somehow installed wrong.

Not sure new banjo bolts if a different from OE is right? Can't know would need to look carefully myself.

If the old ones took a lot of force IDK if that bothered caliper pins even if not removed? Those IMO would have removed and regreased while there are a much more common failure - the type on brackets with small bellows to keep water and dirt out. Those fail the pins will fail soon after.

That would cause pulling if cross system (IDK) would pull to stuck one then maybe switch when that one gets too hot to the other.

Note: Hard to feel pull from a stuck rear brake if a problem after a drive if prudent to drive at all one wheel is warmer or smells the other doesn't there's a problem to fix,

Tom



sdsusnowboards
Novice

Sep 16, 2022, 3:01 PM

Post #9 of 10 (427 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

Hi all,
Just coming back to post the solution.

The problem resolved after using a Motiv power bleeder to the master cylinder, creating positive pressure, and cracking loose the lines at the ABS module. I saw no evidence of any air coming out with the fluid, but nevertheless the brakes were restored to their factor feel.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 16, 2022, 3:16 PM

Post #10 of 10 (424 views)
  post locked   Re: Soft Spongy Brake Pedal After Installing Soft Lines  

Yep, that's usually necessary on today's systems. Many require a professional scan tool to open the ABS solenoids for bleeding also.

I'll close this now as solved.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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