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[Tutorial] Changing the Master Cylinder

I recently had the issue of where my 1970 Cutlass SX was having issues stopping.  Luckily, there was no accident involved.  I took it to NTB to get it checked out and they said the master cylinder was leaking and my fluid was bad. I wasn't going to argue against that, just about the fact they wanted to charge $500. This tutorial goes over the process of how to replace your master cylinder. If you have any questions, please just ask with a comment.

Disclaimer: Since this involves the brakes, I just want to ask you to be very careful when testing your car and seeing if it stops.  This (along with flushing / bleeding the brakes) fixed my problem but may not fix yours.

Step 1: Is this really my problem?
First, you have to decide if you really need to change it at all. I had what looked like a leak going down my power booster (the think behind the master cylinder) and my brake fluid actually look just like old coffee (below).  With a master cylinder only costing about $22 dollars (I kept my old one) I figured why not.

Step 2: Take out the brake lines
Put an old towel or newspaper below the master cylinder to catch any brake fluid that will fall. Then, there are two brake lines that feed into the master cylinder. You can see one in the picture above. The second one is to the left of it hidden behind my top latch.  Unscrew them and put a tape over the opening to ensure nothing gets into the brake lines.




Step 3: Take out the master cylinder
Now you unscrew the bolts connecting the master cylinder to the power booster.  Its pretty self explanatory and it should look like something below.




Step 4: Get and plug your master cylinder
Grab your new master cylinder and plug up the two opening.  If you read on most instructions, you need to get an adapter and lead tubes from the adapters back to the top of the master cylinder. Now you do not need to do that. You simply need to just screw in the plugs.




Step 5: Bleed your master cylinder
If you have a vice grip, it would probably help quite a bit more. If you are young and cheep, 2 washer pits and a concrete wall will do. Wedge your master cylinder straight up against somewhere where it will stay upright. Fill up both containers with fluid (DOT3).  With something hard (like a tire jack piece), slowly push in the cylinder end of the master cylinder. Slowly retract it and you should see bubbles appear.  Wait about 10 - 15 seconds and do this all over again until you see no bubbles. This took me about 60 times.



Step 6: Installing the master cylinder
Screw back in the master cylinder to the power booster.  Start putting in the brake lines, but not all the way tight.  Have someone slowly push on the breaks until a little fluid leaks out of the break lines and then tighten them all the way.  Ensure you filled the master cylinders all up to about a 1/4 inch of empty space and put the cap on.

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