Chocolate for brakes. The Dreaded Pudding Foot.

[Dudeland]

44 minutes ago, popovm said:

Well, to be clear, the softness throughout the stroke is a different problem. You can safely drive around the slop but the squishiness (aka “puddin foot”, I like that btw) is a safety issue. I’d fix that first. Adding in the pedal box is unnecessary scope creep at the moment. It’s still worth it in the long run but it’ll be more straightforward to focus on one thing at a time: the chocolate puddin you’re squishin with those crocs. 

I agree

Is it possible that much slack that I am running out of stroke? 

 

I bled out the rear callipers with the pressure/power bleeder, then for the last time, I took a chain vice grip and wrapped it around with a bit of wood to protect the piston, and buddy bled them out with the bleeder at multiple angles.

 

I haven't adjusted the parking brakes, but that shouldn't matter with the rear disks.

 

I found my performance pivot.  The pedal box kit is in long-term storage.  I will get it tomorrow. 

 

 

 

 

[Dudeland]

Ok, I just remembered I got a brake pressure gauge for this reason.  I am going to take measurements of the pressures on all four corners and get back to you all tomorrow.   I suspect that the front brakes will have the same pressure, and the rears will be the same 

 

Does anyone have an idea of what sort of pressure I should get? 

 

Thanks.

 

 

[OldRoller]

Even with some 'slop' in the pedal box, with engine off sitting static you should have a firm pedal. The squish indicates some air in the lines absorbing the pressure. 

Bleed the entire system starting with right rear, left rear then right front, finally left front. Bleed until NO air bubbles are seen in the escaping fluid. 

The process took me several hours on the 74... new rear slaves, lines, calipers, mc. The mc has a short throw and small output, requiring a lot of bleeding to completely purge the lines. 

[Einspritz]

IIRC the Blue book has the slop at about a pedal thickness.

 

In addition to the pedal bushings, what no one has mentioned is the linkage to the bell crank forks, the bell crank bushings, and the linkage to the M/C. Each mm of slop at each of those points will be amplified at the pedal.....a lot.

 

That solution is to make new bushings (or an IE kit for the bell crank) and machine bushings for the forks, and/or machine new rods to get ~0.001 of clearance.

 

 

[Dudeland]

Just now, OldRoller said:

Even with some 'slop' in the pedal box, with engine off sitting static you should have a firm pedal. The squish indicates some air in the lines absorbing the pressure. 

Bleed the entire system starting with right rear, left rear then right front, finally left front. Bleed until NO air bubbles are seen in the escaping fluid. 

The process took me several hours on the 74... new rear slaves, lines, calipers, mc. The mc has a short throw and small output, requiring a lot of bleeding to completely purge the lines. 

1)  I did bleed in that order. At least three times (really about 6).   I put a whole litre of  "ATE 706402 Original SL.6 DOT 4 Brake Fluid" as per @TobyB's recommendation. 

 

2) I wasn't getting any bubbles.

 

3) Even bled at the master cylinder. 

 

I really, really, really tried hard not to have to write this post.  Because I am posting this, I am ready to throw in the towel, or look at other bits of the system between my foot and the wheels, and the only thing I haven't been through at least 100 times is the lever system. 

 

The old brake master cylinder felt almost identical, with the same amount of slack.  It didn't look bad at all, and there was nothing leaking out of it. 

 

It also could be that I am pressing too hard on the pedal, I am a big guy.  I don't think that is it has squish at the front, then gets hard. 

 

 

 

 

[Dudeland]

8 minutes ago, Einspritz said:

IIRC the Blue book has the slop at about a pedal thickness.

 

In addition to the pedal bushings, what no one has mentioned is the linkage to the bell crank forks, the bell crank bushings, and the linkage to the M/C. Each mm of slop at each of those points will be amplified at the pedal.....a lot.

 

That solution is to make new bushings (or an IE kit for the bell crank) and machine bushings for the forks, and/or machine new rods to get ~0.001 of clearance.

 

 

I have the bell crank upgrade in my garage.  I tried putting it in but I couldn't due to a tool and space limitation.  I will get it in and see what it feels like. It will be easier now that I have it back on the stands. I have to mod the gas pedal a bit anyway, as the throw on the gas pedal is quite short.

 

I think that the beehive just got kicked. 

[Dudeland]

Oh, and as an FYI, to rebuild the rear MKII calipers, the best way I found to get the outer piston dust cover on is to stretch out the cover, take a zip tie, and zip it just below the innermost below. 

 

Then, slide it down until the lip of the seal is just below the piston.

 

Then, gently move the dust cover seal in the groove. Once it feels good, push down hard to lock it in place with the piston. I used a grip-style clamp to apply pressure to the piston, then got the water pumps out to rotate the piston back into the callper. 

 

 

[TobyB]

If it's squishy, you've got air or movement- or both.

 

Unbedded brake pads can indeed add to total pedal travel, as the surface of the pad itself

is a bit uneven before it mates to the rotor.  It's not going to be the pudding, though, as it will eventually

gel into fruitcake...

 

Have you tried tapping on the calipers with a hammer?  It dislodges small bubbles that cling to dry castings...

 

Honestly, I find that I have to use the brakes on any car I've had 'go dry' pretty hard- and then rebleed- to get

 a truly solid pedal.  There's just too much air floating around in there in tiny little bubbles, and it all adds up.

 

Bleeding those rear calipers is a pain in the butt, isn't it?  Don't you have to take them off and turn them so the bleeder faces up???

 

The last thing to make sure is that the main cylinder's being allowed to completely release.

there's an adjustment in the booster, and if it doesn't go just  a titch slack, the piston may not retract all the way,

which will lead to everything from difficult bleeding to self- applying brakes.

 

t

chocolate pudding foot's the worst.

[Son of Marty]

42 minutes ago, TobyB said:

Have you tried tapping on the calipers with a hammer?  It dislodges small bubbles that cling to dry castings...

This, the bubbles stick to the sides just the same as the bubbles that stick to your legs in a hot tub.

[Dudeland]

5 hours ago, TobyB said:

If it's squishy, you've got air or movement- or both.

 

Unbedded brake pads can indeed add to total pedal travel, as the surface of the pad itself

is a bit uneven before it mates to the rotor.  It's not going to be the pudding, though, as it will eventually

gel into fruitcake...

 

Have you tried tapping on the calipers with a hammer?  It dislodges small bubbles that cling to dry castings...

 

Honestly, I find that I have to use the brakes on any car I've had 'go dry' pretty hard- and then rebleed- to get

 a truly solid pedal.  There's just too much air floating around in there in tiny little bubbles, and it all adds up.

 

Bleeding those rear calipers is a pain in the butt, isn't it?  Don't you have to take them off and turn them so the bleeder faces up???

 

The last thing to make sure is that the main cylinder's being allowed to completely release.

there's an adjustment in the booster, and if it doesn't go just  a titch slack, the piston may not retract all the way,

which will lead to everything from difficult bleeding to self- applying brakes.

 

t

chocolate pudding foot's the worst.

 

The rear callipers are PIA, but I used a chain-type vice grip and performed the procedure I mentioned before, and it was way better. 

 

I did check the pin that pushes on the plunger, and there was a clearance; I could easily put the new M/C on and butt it up to the booster without any spring resistance.

 

I banged the rear calipers all over and did get a slight whisper of bubbles, the size of a pinhead.  

 

I am not a fan of fruit cake. 

 

The system, by accident, went dry as the clamp that I had on the right rear calliper popped off and barfed out the piston and all the brake fluid. 

I used the opportunity to replace the dust cover, pressure seal and piston, although the old one was fine. (Oh yeah, it was such a fun time.)

 

 

 

 

 

 

 

 

[Dudeland]

5 hours ago, Son of Marty said:

This, the bubbles stick to the sides just the same as the bubbles that stick to your legs in a hot tub.

 

I feel that I banged them around enough to get all the bubbles out. I am going to let things settle a bit and perhaps try again later this week. 

 

I need to order more brake fluid. 

 

 

[popovm]

Man, good onya for persevering . I have been lucky and haven’t had problems with bleeding car brakes but I’ve had hydraulic bicycle brakes give me trouble and it’s maddening. 

[Dudeland]

Is this the solution?

 

 

 

 

[2002iii]

Did you remove the residual pressure valve from the master cylinder? If you don't it can cause your rear brake calipers to drag.

 

Did you bench bleed the master cylinder?

 

Rubber or stainless brake hoses?

[Dudeland]

8 hours ago, 2002iii said:

Did you remove the residual pressure valve from the master cylinder? If you don't it can cause your rear brake calipers to drag.

 

Did you bench bleed the master cylinder?

 

Rubber or stainless brake hoses?

 

Residual Pressure valve: I don't think the Tii one I got came with one, but let me double-check.  I know I drilled out the one on the original M/C

 

Bench Bleed M/C:  No I didn't have the gear to do it, but I may have to rip it out.  Definitely on the table 

 

Rubber or Stainless:  Stainless from Ireland Engineering.