I am going to install an used Master Cylinder on my 1984 MB 300SD.
Before remove the older one from my car and install the used part on it, I would like to make sure that it is working properly to don't waste my time.
Please send me some info about what kind of test can be performed in a DIY base before go ahead wit the job. I also heard that the best way to have the brake fluid changed is to let the old one to drain by gravity overnight leaving the fluid reservoir and the drain plugs at the calipers opened. How much is this true?
Thanks everyone.
Nyko46

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Nyck - TX - USA

Search the DIY section. Like this one:
Brake:

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too many w123's
84 280 SL 5 speed

How much does a new one for your car cost ?

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I have no ideia baout cost for new one.

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Nyck - TX - USA

$55.83 for a Meyle. $87.29 for a FTE

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too many w123's
84 280 SL 5 speed

Just as easy to fit a new seal kit before it goes on the car.

Anyway , this is what the police drivers do in the Uk before taking the high speed patrol cars out.

Get in the car and place foot on the brake pedal and press down hard and keep it pressed down hard for around a minute,it should stay in the same position and not sink down.

Keeping the foot on the pedal hard start the engine,the vacuum will pull the pedal down a bit upon where it will then go stiff as it was before the engine was started.

Keep your foot down hard for the next 3 minutes,in this time if the pedal has not moved any further down then all is ok.

Now this may work out fine when tested on the donor car but sods law dictates the seals will give up when bleeding the system on the new car it is fitted to,so it would really pay to fit new seals.

It sounds very interesting and I will go from there.
I really appreciated your response.
Nyko46

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Nyck - TX - USA

I hope someone paid you to take that used master cylinder, that's the only way I'd put one on a car. $55 is cheap insurance, even $100 is cheap insurance especially when you get into the end result of master cylinder failure.
The cause of failure is corrosion- It builds up in the master cylinder bores outside the normal travel range, and when you go to bleed it you typically have full travel, so the corrosion cuts the seals. You really need to hone the master cylinder and reseal it, but the cheapest reseal kit I have found is $135 plus you need a master cylinder hone and the knowledge to use it.
The sole way to actuate your service brakes is not a place to cut corners-

IMHO .... ANY used brake component needs to be rebuild prior to installation. Its just not worth the alternative of not and then needing a new car.

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."