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Favali 06-01-2003 04:50 AM

Brake Master Cylinder Replace
 
I recently discovered that my Brake MC has a small leak where it mates with the power servo unit. Presuming it is time for a replacement (as a rebuild is not worth it), I am looking for any advice, etc.

It appears straightforward and I suspect I will have to suck out some fluid from the belly of the servo unit (thank you Mr. Turkey Baster). However, does anyone have any tricks on bench priming the MC so I do not have to bleed all that air through the system?

Plus ... any experience with those one-handed brake bleeders?

TIA ....

Paradiso 06-01-2003 05:25 AM

Rob:
I got the Gunson eezibleed last year.
http://www.aep.bigstep.com/eb.gif

It uses pressure from the spare tire to push the fluid through. Worked very well. Its a bit of a pain yanking out the spare, but it all hooks up easily. The one downside is that the bottle that holds the fluid could be bigger. You still have to have someone keep an eye on the fluid level or you'll start pumping air INTO the system!!

Favali 06-06-2003 06:00 PM

MC replaced today ... no system bleeding required as I had received a bit of advice from the Alfa Digest on how to replace it without bleeding the system.

Also picked up a case of Spirax HD and replaced the differential fluid. Transmission is next ......

JoeCab 06-06-2003 09:02 PM

Paradiso,

I also have that Gunson system. The thing is, it's not just easier, it's actually a better bleed. I have run into situations where no amount of pedal pumping would dislodge some air bubbles, but a pressure bleed did so easily!

The only thing I would recommend is that you use some pretty low air pressures on older Alfas as sometimes 10-15 psi can be too much for the reservior and associated rubber seals to take.

The way I deal with the issue of running the remote reservior dry is that I have the same size bottle as my catch can. When the catch bottle is close to full, the reservior is almost empty.

120 06-06-2003 11:00 PM

I'm sure the ez bleeder works well, just be sure you have a GOOD connection. On a ratty car the PO must have used one and it blew off spraying brake fluid all over the engine bay. The paint looked like a pleated curtain.
I rebuilt the MC and replaced boosters and tried every fashion of bleeding but had no luck. Could not get the pedal to firm up. With the bad threads on the reservoir I couldn't use pressure, so I used a vacume pump at the bleeders. Turns out somewhere the lines were not tight enough, they wouldn't leak fluid but would suck air. Once I retightened everything I got it to work. I tried to bleed that car for so long, its as if my mind was working at the speed of light.
real ratty 69
Bruce

John M 06-07-2003 12:58 AM

I don't know if this would work for the S4 spiders, but on my 78 MC rebuild and reinstallation I just bled the system from the output brake lines where they connect to the MC. On my car they are vertical and when they are disconnected only the MC dumps fluid of any consequence. I primed the MC with the tubes off once the MC was reinstalled on the booster by slowly pumping the brake pedal. A couple of catch cans and rags and extra brake fluid came in handy. I had someone press on the pedal slowly as I quickly reattached the brake lines. Once the lines were tight, I had my helper release the pedal. I then loosened one line at a time to bleed out any air and had my helper again press the brake pedal slowly. Once I was getting all fluid from the loose fitting I then tightened the line. I repeated this process per line. You will know you are getting it done right as the pedal regains its firmness. Its a messy process, but it works. I again stop on a dime.

John M

Favali 06-07-2003 03:22 AM

John's method is exactly what I did. Since the 3 brake lines (1 for each front wheel and 1 for the rears) are below the MC reservoir, they retain the fluid with no air. I bled the MC as John noted and it worked great. After 3 bleeds on the connections, the whole system came up to pressure.

Roadtrip 06-11-2003 02:54 PM

Rob-
How old was the fluid in the system? If it's more than a few years old, it's probably wise to flush the whole system to get the water out of it. Brake fluid absorbs water and holds it in suspension.

Favali 06-11-2003 03:01 PM

The brake fluid and clutch fluid was fully replaced last Spring.
Brake and clutch fluid should be replaced every 2 years. Particularly in my case as the car is stored from October to May.

With the new MC and new resevoir ... plus I bled the brakes as a precaution, I have another new "load" of fresh fluid in the system.

BTW .... all seems fine and works great. And with the Spirax in the tranny and diff, I have no 2nd gear problems.


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