An update on the replacement of the brake master cylinder and servo/slave cylinder in the 72 S3. I finished the parts installation without further problems, including new vacuum hoses to the vacuum tank and new PDWA unit and brake fluid reservoirs with hoses, all from Barratt. The dreaded bleeding turned out to be quite simple with my Swiss Vacula air-powered vacuum unit. I did the front brakes first, starting on passenger side. I did the rear brakes by removing the access plates in the rear of the storage area behind the front seats. A 90 degree bleeder hose works best on the rear bleeders and vacuum bleeding process was uncomplicated. I got a good firm brake pedal with no problems. I had some slight brake fluid leakage at the new PDWA unit initially but solved with a little tightening of the brake line nuts on the PDWA, fortunately still reachable with everything assembled. Things still look good after a short test drive. I appreciate all I learned from others on this site!
Is this the same as ‘MityVac MV7300’ that is available on Amazon. Has anyone had success with this unit, or recommend another?
New brake/clutch line installations are my first spring job this year and will be faced with bleeding all systems.
Thanks in advance.
I believe all of these vacuum bleeders work the same way, creating enough vacuum in a small tank to pull brake fluid and air out of the open bleeder valve on the brake caliper. If you have an air compressor, the units which use air to create the vacuum are easiest to use. Some units use a hand pump to create the vacuum—-I have not used that type but they reportedly work. A U-Tube search will turn up plenty of how-to videos. At each caliper, I like to start with the master cylinder full of fresh brake fluid and draw it down to 1/4 to 1/3 full at each caliper. Don’t draw down too far or you will suck new air into the brake line. You will still see air bubbles at the caliper bleeder because vacuum draws air around the bleeder threads but that does not mean there is air in the brake line. When finished you should have a nice, firm brake pedal with the normal amount of travel. There are some vehicles where the vacuum method does not work and pressure bleeding is required—-I have not seen a good explanation for that.