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Old 02-15-2001, 11:55 PM
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Join Date: May 1999
Location: Sacramento, CA
Posts: 1,416
I just had my '87 300E in for some brake work - front rotors and pads, plus a fluid change - and I've noticed that twice in the past week the pedal would travel two or three times as far before the brakes would engage. If I waited a moment, or pumped the pedal, pressure would come back to normal. I checked the reservoir, and the fluid is new, all the way up to the "max" line. Is this an air bubble stuck somewhere in the system? Any chance it would work it's way out? This hasn't been a very repeatable symptom.

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Old 02-16-2001, 12:10 AM
Posts: n/a
Master Cylinder

What you are experiencing is not uncommon after the type of repairs you had done.
What has occurred, is over time the master cylinder bore has corroded from the water the brake fluid as obsorbed.
With new pads installed the piston in the master cylinder is resting at a different location in the bore than before.
The seal is setting on the rust, and as such it has it's pressure bled off.
This is your failed pedal sensation.
The cure is rebuilding the master cylinder, provided the bore can be honed clean.
If not the bore can be sleeved, using bronze or stainless steel.
Rebuilt master cylinders are available, exchanging your's for thier's.
Check it out.
Happy Trails Beep Beep from Houston!!!
Donald, El Cheapo
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Old 02-17-2001, 12:39 AM
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Join Date: May 1999
Location: Sacramento, CA
Posts: 1,416
Wow, that was quite the informative answer. I'll have to look into that - is there any particular reason this happens intermittantly, rather than all the time?

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Old 02-17-2001, 02:40 AM
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Moderator Incarnate
Join Date: Apr 2000
Location: Lake Geneva, WI.
Posts: 1,676
the same thing happened to me on my 87 300E. i blamed it on Midas and they gave me a new master cyl!
Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320

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Old 02-17-2001, 11:44 PM
Posts: n/a

The intermentant pedal fade is from the position of the piston in the bore, the disturbance of the gobbley goop and the amount of pedal apply pressure your Big ole right leg and footsey apply.
And if you take your Benz to Midas for brake service, shame on you, the devil will get you.
And you should check this out, I could be so off that it might be the wrong air pressure inthe spare tire.
Happy Trails Beep Beep from wild guess Houston!!!
Donald, El Cheapo
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