Dark brake fluid = bad master cylinder?

1999 4Runner SR5 V6 - 86,000 miles
A mechanic recently told me that the dark brake fluid in my resevoir is an indication of a bad master cylinder. I could not get him to change
the brake fluid without replacing the master cylinder, and he refused to work on my front brakes unless I also replaced the master cylinder. This would have increased a $500 job to $900+.
I agree that the brake fluid should be changed, but is it a bad idea to bleed dark brake fluid through ABS brake systems (and the new calipers that he also wanted to add on)? Even if he replaced the master cylinder, wouldn't this dark brake fluid already be throughout the entire brake line? He was adamant that the master cylinder was bad based on 1) dark brake fluid and 2) increased downward brake pedal travel.
Am I crazy, or is this overkill?




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Overkill. Granted, sometimes the act of flushing out the MC can kill it; but that is rare. The low brake pedal probably is rear brakes need adjusting. Find another shop.
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Stephen W. Hansen
ASE Certified Master Automobile Technician
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Get a second opinion if you're not sure of this guy. $900 seems high to me, a former part time shade tree mechanic, but then who knows with these new fangled cars.
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Not really. ABS brake systems are not that sensitive.
Even if he replaced the master

Yes, unless you completely flush all of the lines.
He was adamant that the master cylinder was bad

Brake fluid will get dark over time, which is why it is a good idea to flush every 2 or 3 years.
Like Steve H. says, increased downward brake pedal travel is due to normal wear.

Overkill. Find another shop or do it yourself.
--
Ray O
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On Wed, 09 Nov 2005 07:27:58 -0800, James wrote:

Man, if that's true, I gotta LOT of Bad Cylinders!
Brake fluid darkens with age. I have often posted instruciotns for making a brake beelder kit...I'm not that ambitious tonight. Try this:
http://www.garageboy.com/bmw/bleeder.html
You can also use it for flushing the fluid, just remember to keep adding new fluid so you don't run the cylinder dry.






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