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914World.com _ 914World Garage _ Putting in a new Master Cylinder, a few questions

Posted by: PDXMike Mar 30 2011, 05:32 PM

I've been reading about how much of a pain putting in a master cylinder can be. Is it worth the effort to simply pull the fuel tank? Which is worse, the time to pull the tank, or the frustration of trying to get the lines from the reservoir hooked up in place?

What about bench bleeding? Any tips on a temporary reservoir to use while bench bleeding? Do I need to bench bleed?

Any tips or tricks? Any "gotcha"s to look out for?

Thanks,

Mike

Posted by: SLITS Mar 30 2011, 05:44 PM

it's installed from the bottom ... no need to pull the tank.

Two things:

Make sure that the push rod is actually in the MC on re-install

The hoses are hell to get in .. they should "snap" into place (assuming you are using an ATE MC. If it's the Uro, take the rubber connectors and washer out of your old MC.

Once that is done, fill with brake fluid, crack the fittings on the MC outlet to brake lines and let them drip for a while. Tighten them and go on to your favorite bleeding method.

Posted by: sfrenck Mar 30 2011, 06:17 PM

I had my tank put back in with the car ready to go for the first time - just to find out I needed to change the M/C. I couldn't get the plastic tubes from the resevoir to push into the M/C without taking them out of the car. I was able to get the tank up on the driver side without removing the whole thing (left the fuel hoses on).

Hardest thing to lifting one side of the tank was to drain it.... and take the front hood off for enough room to pry the tank up.

Posted by: Prospectfarms May 14 2011, 01:25 PM

This thread is 6 weeks old but I'm adding a few comments from my experience with master cylinder replacement and/or the re-pressurization of hydraulic brake system:

1) SLITS helpfully commented: "Make sure that the push rod is actually in the MC on re-install."

It's also important to remember to re-connect the push rod to the brake pedal before installation of the new MC. Most people never disconnect it in the first place but the Haynes procedure on MC replacement directs disassembly of the cotter pin connection and removal of the push rod from the brake pedal assembly before removing the old MC. Once the new MC is reinstalled, the push rod cannot be reattached. It looks like it should, but there is not enough clearance at the cotter pin connection.

Several people have posted problems with initial pump-up of brake system after MC installation. The most quoted response is to "bench bleed" the MC, but I don't think that is why most people experience that problem. Failure of a hydraulic system to pressurize after its been drained can often be traced to an air leak somewhere in the system. Forgetting to replace the copper washers on the banjo fitting is one example. Another is a leaky caliper.

(AMHIK)

A properly operating brake system should pressure-up after refilling with a few depressions of the brake pedal without having to bleed anything. Bleeding brakes is obviously important, but should not be necessary simply to get fluid into the MC.

My two cents