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olaaf

trouble with spec iron/S197 rear calipers

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olaaf

2 weeks ago it was time to change the rear pads, I did so and then had a soft pedal, no matter how much I bled the system. I bought a new set of calipers, and bled them using the FSM procedure (regular bleed, then extend the pistons halfway out by removing 1 pad, screw them back in with the bleeder screw open). I get a TON of air bubbles every time I do this, over and over again. So much air, that I bleed through about half a quart of fluid per caliper. I’m using a motive pressure bleeder. Thinking the master was bad, and sucking in air when pumping the brakes down to screw the piston back in, I replaced the master and bench bled it, but no change.. kind of at wits end here..

 

Any experience with this?

 

rearbrakes.PNG

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stevepoe

So you had perfect operating brakes before going to change the rear pads ? Returned the rear calipers to install new pads. installed new pads and never got a pedal back after that ... you did nothing else. no bleeding or anything ?

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olaaf

Brakes were perfectly fine beforehand..

 

here is what i did step by step

 

(Wednesday night)

 

1- Remove right rear caliper, put it on the bench and figure out how to install pads. Messed around with c-clamps until I realized you need to screw in the piston.

2- Harbor Freight Trip- purchased a brake caliper screw-in tool kit

3- Opened bleeder, Screwed in piston on bench, pushed it all the way in (too far?)

4- Installed pad on right rear, re-installed caliper w/ fresh crush washers

5- Left rear bleeder opened, screw in piston with caliper feed line still attached

6- Bleed whole system

7- Rock hard pedal w/ engine off- soft pedal with engine running

8- Re-bled everything, same status

9- Re-bled again, same status.

10- Cursing.

 

(Thursday Morning)

 

1- Purchased 2 new rear calipers. Installed w/ pads

2- Bled calipers

3- Same status

 

(Friday Morning)

 

1- Purchased and Installed new master

2- Bled calipers

3- Same status

 

(Next Week Saturday)

 

1- Bench Bled Master

2- Reconnected all lines, Bled whole System

3- Same status

4- Followed FSM rear brake bleed procedure

 

FSM rear Caliper procedure

 

1- Remove 1 brake pad, place a shop towel in it’s place.

2- Pump brakes down until slightly firm

3- Remove caliper, remove shop towel

4- Open bleeder, connect motive power bleeder, screw in piston

5- Tons of air bubbles

6- Repeat

7- Repeat

8- Repeat

9- It never ends

 

(Sunday)

 

1- Right rear caliper explodes (dust boot around piston) during repeat procedures. Possible hyper-extending? I noticed a large amount of what looked like rust in the fluid prior to this, must be rubber bits from failing seal/boot..

2- Go to autozone, pick up brake new right rear caliper

3- Repeat FSM procedure.

4- Cursing.

 

Diagram.PNG

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johnny c

Something isn't right.

first thing that i wonder is. during the pad install, did you lose enough fluid to allow air into the ABS system?

 

2. How are you bleeding the system? are you using a new tool or speed bleeders?

 

Air is entering the system at some point. It's hard to tell where. I'm wondering if your using some kind of vacuum pump that it's not bleeding the system correctly or a speed bleeder that isn't working properly. At this time i'm not thinking you have a bad part or equipment on the car. if you had a leak the pedal wouldn't be only soft, it would be going from soft to non existent.

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wpbcobra

Did you make sure you lined up the piston and the back of the pad up. i dint once and had the same problem that your having.

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olaaf
Did you make sure you lined up the piston and the back of the pad up. i dint once and had the same problem that your having.

 

yes.. small slots in the piston lines up with the nub on the pad..

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stevepoe

Have you tried bleeding the system without you contraption to assist you ? meaning 2 people up down etc etc and bleed the complete system front and rear ?

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Ed M.
Did you make sure you lined up the piston and the back of the pad up. i dint once and had the same problem that your having.

 

yes.. small slots in the piston lines up with the nub on the pad..

I grind those nubs off the pads before I install... This eliminates this requirement.

 

Ed

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snakebit

Did you swap to ss lines during this pad change?

John

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olaaf
Did you swap to ss lines during this pad change?

John

 

before the pad change, last year when i installed the M-2300 brembo kit..

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olaaf
Have you tried bleeding the system without you contraption to assist you ? meaning 2 people up down etc etc and bleed the complete system front and rear ?

 

no, i've always used the pressure bleeder.. though i just got a set of speed bleeders that are going on this weekend and will give the 2 person method a try.

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robss96dcm

Have you tried actuating the parking brake to help adjust the caliper?

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goindeafonmtx

Pull the e-brake a couple times. Had the same issue on an SN95 car. I bet that is the issue.

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olaaf

yeah, i've rocked the parking brake back and forth. i can now get clear fluid via speed bleeders out of every caliper, but the pedal is still soft when running.

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dtanker65

I have always used the 2 person method, but I do it differently since I am always servicing and flushung the brakes every few track sessions.

 

I bought some 5/16" clear tubing 12-18 inches long and took empty water bottles with the caps drilled to fit the tubing. Put the tubing over the bleeder screw and route the tubing so it has an arch several inches above the bleeder. Then crack both bleeder screws and pump the pedal. The fluid trapped in the tube above the bleeder prevents air getting in. Close the bleeders and then remove the tubing. I don't try to pump fluid into the bottle then suck it back in to the tube, just pump it out.

 

Works great for flushing too, just keep puming until clear and close the bleeders. Works great for me and no mess, I usually do both rears together then both bleeders on each front caliper together (one caliper then the other).

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olaaf

for what it's worth, i took it to the dealer today and did an ABS bleed, no change. I now suspect the booster (which seems counter-intuitive to a booster failure), as that is the only part not changed. I put a vac pump on the line to the booster, and it doesn't hold vacuum- really strange, because the engine idles fine.

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stevepoe

did you ever figure out your problem ?

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olaaf

No, thanks for following up. I changed the booster, but no difference. Amazing, almost everything in the braking system has been swapped. I have a set of metric bubble flare plugs that I’m using tonight to isolate the fluid circuits and track down the problem. Starting to think about a nuclear option, given the nationals are coming up quick.

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olaaf

Tonight I replaced the master again and I bought a set of metric bubble flare block-off plugs to cut the hydraulic system into pieces and isolate the problem- here is what I’ve found:

 

• The master is good.

 

• The rear circuits are good.

 

• The front circuits through the HCU are good.

 

• The pedal is soft between the output of the HCU to the front calipers. BOTH front calipers are contributing to the problem. If I block off 1 of the fronts, and bleed the other side, the pedal is “half as bad”. if both are blocked off, the pedal is rock hard as expected (rear circuits are still connected)

 

I have installed brand new brembo calipers, stainless lines, PFC pads. i'm seriously at a loss here. i'm down to looking at google maps for the towing route from NYC to rehagen's shop.

 

HCU.jpg

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snakebit

Just throwing this out there. After I swapped to ss lines; the brakes were initially fine. But after a short time I started experiencing problems including a soft pedal. Robert and Mitch Miller kept telling me you need to shorten your rear banjo bolts. Well I finally did and guess what. Better brakes and a solid pedal. Maybe when you replaced the crush washers, the replacements were slightly thinner, and the banjo bolts are too far down in the calipers.

John

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stevepoe

where did you get those block offs ? That is something I need in the tool box

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olaaf
Just throwing this out there. After I swapped to ss lines; the brakes were initially fine. But after a short time I started experiencing problems including a soft pedal. Robert and Mitch Miller kept telling me you need to shorten your rear banjo bolts. Well I finally did and guess what. Better brakes and a solid pedal. Maybe when you replaced the crush washers, the replacements were slightly thinner, and the banjo bolts are too far down in the calipers.

John

 

i'll take them apart/inspect and double up the crush washers tonight- thanks for the input.

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snakebit

Take one side apart, insert the bolt back into the caliper until it bottoms and measure. Then measure the brake line and crush washer thickness. Should be a quick tell...or like you said, add a crush washer to the caliper side.

John

 

[ quote=olaaf]

Just throwing this out there. After I swapped to ss lines; the brakes were initially fine. But after a short time I started experiencing problems including a soft pedal. Robert and Mitch Miller kept telling me you need to shorten your rear banjo bolts. Well I finally did and guess what. Better brakes and a solid pedal. Maybe when you replaced the crush washers, the replacements were slightly thinner, and the banjo bolts are too far down in the calipers.

John

 

i'll take them apart/inspect and double up the crush washers tonight- thanks for the input.

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snakebit

Any luck?

John

 

 

 

i'll take them apart/inspect and double up the crush washers tonight- thanks for the input.

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