Soft brake pedal (BBK install)

[MildSeven]

I finally installed the IE Wilwood 13" BBK kit, i bought 2nd hand new. I changed my master cylinder for the single line MC, included, installed new brakes and bled line, etc.

 

I took the car for a spin, the pedal was soft and the car would not brake well. I checked again for leaks, everything looked fine. I thought maybe there was still air in the lines, re-bled the lines today.

 

Went for a spin, same thing, pedal started firm but then became soft and car wouldn't brake well, same symptoms as 1st test drive.

 

I didn't bench-bleed the "new" MC, (1) could this be cause me my issues? I had read (on the faq) that it wasn't necessary.

 

(2) should i bench bleed this MC or is the MC just bad?

(3) Should I just install my old MC and plug the extra 2?

 

Thanks,

Anthony

 

Edited September 1, 2019 by MildSeven

[Doug Riparetti]

I had ZERO luck with the E21 master cylinder when I did my big brake kit upgrade, I ended up doing a brake booster delete, modified the bell-crank to change the peddle ratio, an installed a generation 2 Corvette master cylinder with a custom adapter to bolt to the stock pick up point where the existing brake booster was mounted.

 

Brakes work AWESOME, and NO proportioning valve for balance was used.

Edited September 2, 2019 by Doug Riparetti

[Dudeland]

5 hours ago, Doug Riparetti said:

I had ZERO luck with the E21 master cylinder when I did my big brake kit  upgrade I ended up doing a brake booster delete, modified the bell-crank to change the peddle ratio, an installed a generation 2 Corvette master cylinder with a custom adapter to bolt to the stock pick up points where the existing brake booster was mounted.

 

Brakes work AWESOME, and NO proportioning valve for balance.

Dude you just blew my mind.   Do you have picks?  Pm me,  Sorry I don't want to hijack the thread. 

 

[Doug Riparetti]

 

 

Edited September 2, 2019 by Doug Riparetti

[xr4tic]

Maybe talk to IE first before you start swapping the master cylinder.  I wouldn't plug the lines, a 2-into-1 T would probably be best.

 

Is there a lot of meat left on the pads?  Could still have air trapped in the lines, what's your bleeding method?

 

I didn't bench bleed my new master, used a pressure bleeder, no issues.

[MildSeven]

I had ZERO luck with the E21 master cylinder when I did my big brake kit upgrade, I ended up doing a brake booster delete, modified the bell-crank to change the peddle ratio, an installed a generation 2 Corvette master cylinder with a custom adapter to bolt to the stock pick up point where the existing brake booster was mounted.
 
Brakes work AWESOME, and NO proportioning valve for balance was used.

Thanks Doug.

I don't really want to go down this route. Will see if I can get things sorted before going all custom

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[percy]

15 hours ago, MildSeven said:

I finally installed the IE Wilwood 13" BBK kit, i bought 2nd hand new. I changed my master cylinder for the single line MC, included, installed new brakes and bled line, etc.

 

Went for a spin, same thing, pedal started firm but then became soft and car wouldn't brake well, same symptoms as 1st test drive.

 

I didn't bench-bleed the "new" MC, (1) could this be cause me my issues? I had read (on the faq) that it wasn't necessary.

 

(2) should i bench bleed this MC or is the MC just bad?

(3) Should I just install my old MC and plug the extra 2?

I

 

Not all brand new master cylinders are perfect and this is likely true for second hand hydraulic parts.  We encountered a similar problem with installation of two new master cylinders for a different make vehicle, albeit ATE units.  The only available replacement unit (rebuilt) worked well out of the box and oiled wrapping paper.  I do not often replace master cylinders.  However, I would be inclined to bench bleed most if I have reason to suspect the unit has been sitting and possibly prone to drying out due to unwanted environmental exposure or poor handling.  But I am probably in the minority.  It can be slightly messy, but to the extent it may prevent a "dry start", it could not hurt.

 

You did not describe your bleeding method.  In you situation I would consider bleeding with a helper pumping the brake pedal rather than other methods to possibly eliminate a concern within the cylinder bore or a slightly deformed piston seal/s.  However, since you have driven the vehicle, it is likely that you have achieved the same result, in which case I would R&R the master or reinstall the old unit.  For obvious reasons, if your older unit worked well and maintained pressure, why not give it a go?  Of course, if the bore is sized differently, pedal effort and travel will be different too.  Naturally, if you have a downstream system leak (or weep), e.g., calipers, wheel cylinders and/or flex lines - your next action lies in that direction.

 

 

[MildSeven]

Maybe talk to IE first before you start swapping the master cylinder.  I wouldn't plug the lines, a 2-into-1 T would probably be best.
 
Is there a lot of meat left on the pads?  Could still have air trapped in the lines, what's your bleeding method?
 
I didn't bench bleed my new master, used a pressure bleeder, no issues.

Thanks for the reply.

I'll call IE tomorrow. The pads are new.

I had someone pump the brakes 3 times and hold, while I opened the bleed valves. I had a bottle with a line submerged in brake fluid.

I did this on Saturday (flushed the old fluid out), the pedal felt firm til I went for a drive Sunday morning.

Note: on 1 occasion when slamming the brakes they locked up.

I re-blead on Sunday, the pedal felt nice and firm. Then same thing once I went for drive.... pedal was soft.

Slow tear,
Anthony

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[Doug Riparetti]

11 hours ago, Dudeland said:

Dude you just blew my mind.   Do you have picks?  Pm me,  Sorry I don't want to hijack the thread. 

 

 In my opinion, the E21 brake master cylinder does not put enough volume, does resulting in a soft pedal. 

[TobyB]

So, Ireland Engineering has sold a lot of different parts over the years,

and this year's "BBK"  may differ significantly from last decade's  "BBK"

 

There are lots of variables, is what I'm saying.  I've used the E21 master,

the stock master, and Tilton masters, and they'll all work.  If you're getting

a solid pedal today, and a soggy pedal tomorrow, that points at air getting in

somehow, or the calipers over- retracting.  Yes, it happens.

 

You'll need to troubleshoot what you have-  first would be:

when the pedal goes soft, does a second quick pump get it up to the

top and firm (over- retraction) or just 'up some and still spongy' (air)?

 

If you do choose to use your dual master, DO plug off the unused lines-

that will allow the dual master to still be dual.  Tee- ing it will make it effectively 

a single circuit, just like a '65 Chevy pickup.

 

hth

 

t

 

[MildSeven]

Thanks Toby.

Should I try to "bench" bleed to e21 MC (while it's in the car)?

Or the bleeding I did would've removed all air from system?



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[MildSeven]

So, Ireland Engineering has sold a lot of different parts over the years,
and this year's "BBK"  may differ significantly from last decade's  "BBK"
 
There are lots of variables, is what I'm saying.  I've used the E21 master,
the stock master, and Tilton masters, and they'll all work.  If you're getting
a solid pedal today, and a soggy pedal tomorrow, that points at air getting in
somehow, or the calipers over- retracting.  Yes, it happens.
 
You'll need to troubleshoot what you have-  first would be:
when the pedal goes soft, does a second quick pump get it up to the
top and firm (over- retraction) or just 'up some and still spongy' (air)?
 
If you do choose to use your dual master, DO plug off the unused lines-
that will allow the dual master to still be dual.  Tee- ing it will make it effectively 
a single circuit, just like a '65 Chevy pickup.
 
hth
 
t
 

Upon pumping the pedal...sometimes the pedal will retain some firmness (like when parked), but 95% of the time, no.

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[Son of Marty]

Do you have the drum brake pre-pressure check valve on your rear brake outlet. 

[MildSeven]

Do you have the drum brake pre-pressure check valve on your rear brake outlet. 

I'm not sure. But when comparing my old vs new.  

The rear line had this (photo) which has a large thread size... the brake line threaded to this, then to MC.

 

 

EDIT. While looking at this... I realized I have the rear & front passenger brake lines mixed up on the Master cylinder.

 

Before I swap them (tomorrow evening), can anyone confirm if this makes a difference?

 

 

 

[Son of Marty]

Yes that needs to go to the rear brakes it prevents the shoes from retracting to far from the drums to reduce brake pedal travel, switching the lines will help your problem,