Brake Bleed Q: trois

SuffolkD at SuffolkD at
Wed Sep 8 15:22:57 EDT 2004

Probably, the simplest item is to: point out your speculation as to the 
workings of my RR caliper (both worn even to the backing plate) and even 1/3 depth 
EACH, PRIOR  to a fourth track event, with no torn guide boots and BOTH pins 
"floating" smoothly in/out.................By this statement of yours: 
"Assuming that the rear pads were changed on both sides at the same time (I don't 
necessarily, DFI if IAB!), this symptom indicates that this RR caliper is gummed 
up and not freely releasing or/and the other side, LR is so gummed up and has a 
frozen piston."

The RR piston worked out under pedal pressure (test) during the R&R 
disassembly AND I learned about the ratching of the E brake mechanism affect to the 
piston during disassembly.  The hydraulic principles worked fine then.  No frozen 
caliper (on the guide pins) and no frozen piston: from either pedal effort or 
Ebrake lever ractheting.

Agreeing with you on some of these points may put a feather in your cap ( you 
knowledgable devil you :-) ) but it won't give me the answers to "WHY?"  
Particularly to the MC and the lack of fluid coming out while draining the rear 
calipers using the bleeder screws.

These Q's you have not answered but retorted with: "A waste of precious 
thought. "

When a complete overhaul will correct the entire brake systom performance 
issue and possibly mask the precise cure, that's why I seek individual points of 
the system to figure out what is happening.

I ask because I seek knowledge

your posts on the 90 20V list and DIY alignments, braces and R&R info are 
legendary, so don''t turn this into DABIYWH:  Don't ask Bernie if you want help?
-Scott by BOSTON  

b.benz at writes:
> >> Bernie:  Legit questions on a new to me car with ~20,000 miles on it. No 
>> maint history except I could tell the brakes were new all 
>> around......certainly NOT original at 133K.
> Why not? 
>  Mine are original at 180K.
> >> 1:  Curious to why so little fluid comes out the rear bleeders.
> A waste of precious thought. 
> >> To post a correction about the previous pad condition for you. 
>> Since I first posted two weeks ago, the actual pad depth was far greater 
>> than first thought.  Except for the RR which had 1/3 pad left in and out. All 
>> had even wear.  
>> Boots intact, greased, clean fluid in the res. 
> Assuming that the rear pads were changed on 
> both sides at the same time (I don't necessarily, DFI if IAB!), this symptom 
> indicates that this RR caliper is gummed up and not freely releasing or/and 
> the 
> other side, LR is so gummed up and has a frozen piston.
> >> The wafer thin pad I referenced was in the dark, on a jack where the 
>> carrier proximity to the rotor (not scored) was close that in the poor lighting 
>> it tricked me. Upon securing the car and sticking my head against the back 
>> of the caliper & carrier where the springs atop the pads go, was I then able 
>> to accurately determine the pad thickness being 1/2 at worst, so R&R was NOT 
>> necessary. Mintex reds standing by.
>> The 
> Henny Penny syndrom.
> >> Just because I can go three plus track events & 20K on the same pads and 
>> rotors before one set out of four wears through?  Considering they were firm 
>> and relatively fade free last week from 122 MPH - 70 MPH stops? "Spirited 
>> use"? Teched three times over two years?  Dot 4?
> These are Qs?  Or expressions of luck?
> >> Since the brakes need attention (vs. before)  new pads, rotors, boots and 
>> grease, bleed and maybe new lines?  MC too someday.
> More Qs!  Overhaul the hydraulics, all 
> calipers, so you know of your starting conditions.
> >> Since the listers have helped with the motor vacuum leaks (chipped now at 
>> 1.6 bar) the indicated 130MPH /actual 122 MPH at Watkins Glen necessitates 
>> working the brakes HARD.  Not surprising.  Since the overall lap pace is now 
>> 15 MPH faster in a 3800 lbs car. 
>> MC bothering you?  Considering the fluid is clear like spring water in the 
>> res, why the panic? 
>> The MC exhibits a specific condition repeatable time after time at a 
>> certain HEAT condition.  Pedal is firm on the street sans the 1" drop when the MC 
>> is beginning to drag.
> Me, bothered you your MC? 
>  Its the fluid condition in the calipers that is of import, not that 
>  in the reservoir.
> >> Someone explained the seals swell.  
>> You don't like that explanation and you may be right, but when heat is 
>> introduced to the MC the brakes drag in ambient above 80 degrees stopped in 
>> traffic. 
>> Something is putting pressure on the lines.  Maybe its something keeping 
>> the piston from returning completely as designed.
> You're just 
> speculating, inasmuch as you know nothing of the hydraulic internals.
> >> Does it hurt to ask those who probably know more than I do? 
>> So why can't this be a functioning system to you?  Certainly there are cars 
>> with more issues out and about.
>> You're 
> speculating that your car may be in slightly better condition than the worst 
> car 
> on the road!  Makes you feel better?
> >> 
>> Bentley lists the "bleed" sequence under 200 Turbo not the 200 3B.  So I'm 
>> double checking and asking Q's. 
>> So I've run into some interesting (to me) stuff.......... no pee and moan.
> Overhaul your hydraulic system first, then ask Qs, 
> for meaningful answers.

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