1) I had the rather classic symptom of brake pedal slowly going to the floor with light pressure applied at a stop. Fix: New master cylinder

2) After replacing the master cylinder with a new unit (not a reman) I was losing fluid. For those following the thread my grandkids, aged 7 and 9 helped me bleed the brakes after the install. Well, the good news is that they bled the brakes with aplomb, the bad news is that the gasket stayed behind on the power booster when I removed the original master cylinder and I didn't catch it. Therefore, I double gasketed the replacement which caused the leak. DOH! I have always watched for this with oil filters, but this was a new one. Live and learn.

Ed in Dallas

 

How hard is it to replace that master cylinder? Mine's doing that same dropping to the floor problem, and I'm also losing a ton of braking power to the point of me having to put a bit of pressure on my ebrake when coming down a hill to a stop light.

 

not hard, 10-15 minutes tops. Good to have a buddy around to help bleed the brakes afterwards though.

 

The job is not difficult, however there are some "gotchas" that you need to be aware of, else you can make things very ugly. This is why I like to take my time.

For instance, I put a drop or two of Kroil penetrating oil on the brake lines at the master cylinder the day before, or PB Blaster will also work. Then, I use a 10mm LINE WRENCH to loosen the lines at the master cylinder. Rounding these will make the job turn bad quickly. After all, who wants to use vice grips when it can be prevented? Don't be tempted to use some crappy open-end wrench on these. You can google 'line wrench' and see a picture

I believe the two mounting nuts are 14mm, don't let the lock washers get away from you when you remove the nuts.

Remove the old master cylinder, clean up the power booster where the brake fluid has eaten the paint, and prepare to install the new unit, AFTER bench bleeding. The bench bleeding instructions will be in the box with the new unit. Don't forget to make sure the gasket has been removed with the old master cylinder!

Be ever so careful, the brake lines are flared and the nuts have fine threads. DON'T CROSSTHREAD. You may have to jiggle a little, but the lines will go on almost all the way down with fingers only. A common problem is that the line sticks into the receiving hole too far and prevents the nut from threading cleanly. Just be patient, when the nut/line fits cleanly into the hole, at the right angle, it will thread in very easily. Did I mention be patient? I actually start the lines/nuts with the unit just barely onto the mounting studs on the firewall to allow a little more movement. Also, don't be tempted to overtighten the nuts once aligned and ready to snug down. You don't have to get ugly on them, but good and snug is required for no leaks.

Tighten the m/c unit onto the firewall and fill the reservoir with fluid. I prefer Castrol LMA because it has Low Moisture Absorbtion which means you don't have to flush it as often. The lack of flushing the old, moisture contaminated fluid is how you (and I, as a result of a prior owner) ended up needing a master cylinder in the first place.

Now get the car in the air, with jack stands securely in place and bleed the brakes on all four corners. There are a lot of sites on the web showing/explaining brake bleeding.

The entire job took me maybe 2 hours, but I am careful and methodical. (just not careful enough to catch a gasket that stayed behind on the first go around!)

Enjoy your new brakes.

All the best,
Ed in Dallas