The brake master cylinder is responsible for distributing fluid from the reservoir to the front and rear brake systems. The fluid reservoir actually sits on top of the master cylinder with hard metal brake lines running out of it. There are a few places where the master cylinder can leak and cause a spongy or soft brake pedal. The inside has several pistons with o-rings and seals that can fail and allow brake fluid to escape. Likewise, the external metal lines also have o-rings where fluid can seep out or let air/moisture in.
This is the 25mm master cylinder upgrade for E30 3 series. It features the larger master cylinder from the E32 750il (#34311156643) with the new required brake line (#34326755585). This set up is used on many track driven E30's to allow for extra stopping power.
This item fits the following BMWs: 1984-1991 E30 BMW 325e 325es 325i 325ic 325is M3 Show More Show Less
