Corvette Master Cylinders - Brake Fluid Keeps Falling On My Floor

Replacing The Master Cylinder

Richard F. Newton Dec 1, 2002 0 Comment(s)
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Once every few weeks I kept having to stop at the local Ford dealer to replenish my brake fluid supply. (You are using Ford brake fluid aren't you?) Right away I knew that this was not a good sign. The other bad sign was that I kept finding peeling paint on my garage floor where the brake fluid was leaking onto the nicely enameled finish.

The first thing I did was buy two wrenches for $70.00. Well, not really. Actually the first thing I bought was a can of brake fluid. Next, I bought a new pressure differential switch for my old brake master cylinder. Then I bought the two Snap-On wrenches. I can explain all of this. Really, I can.

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The first thing is to make sure that all the bleeder screws and master cylinder lines can actually be loosened. If any of these items are going to give you a problem you want to know this now-not half way through the job.

It all started when the shiny enamel paint on the garage floor started peeling. I figured that since it was under the area of the brake master cylinder I should look at what was going on. Sure enough, the underside of the master cylinder was covered in brake fluid. The interesting thing was that it was leaking out of the pressure differential switch. I've never seen that before, but then again I haven't seen a lot of things.

Master cylinders usually leak out of the rear seal. This means that your brake booster is covered in brake fluid. The other failure is when an internal seal breaks down and your brake light goes on. Sometimes you can lose your rear brakes, in which case the rear rotors will get rusty. These are all normal and easy to find.

I went into denial about a failing master cylinder and simply replaced the pressure differential switch. Within the week I was back at my Ford dealer to buy more brake fluid. The next call was to Zip for a new master cylinder. I've always had good luck with Zip when I want OEM parts. I really didn't want to install an off-shore master cylinder in my car. I knew that with Zip I was going to get an AC Delco unit.

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It takes two different line wrenches to break the lines lose from the master cylinder. You're going to need a 12mm and a 14mm flare nut wrench if you have a C4. If you have an earlier Corvette you can use standard wrenches. Which ever you use remember that you want a wrench that won't spread apart as you turn the fitting. The cheap wrenches actually flex if the fitting is difficult to remove. Once you round the fitting you're in serious trouble. You're better off to spend the money on a quality wrench than to spend money fabricating new brake lines.

Master cylinders are easy to replace. In the C4, and all the early Corvettes, it should only take you a half hour to install a new unit. Most shops will charge you for an hour of labor, which is totally reasonable. They may also charge you additional time to bleed all four calipers, which is also a reasonable item.

There are two problems in replacing the master cylinder. First, you can have trouble when you try to break the old brake lines lose from the master cylinder. If you round the corners on these fittings you're in a huge amount of hurt. You can simply start replacing lines half way through the car.

I've installed possibly a hundred master cylinders in my lifetime and the only line wrenches I trust are Snap-On. Normally I'm a Craftsmen type of guy, but when it comes to line wrenches I get the best I can. These things really work. There are a lot of places to save money, but line wrenches are not the best place to balance your budget.

The next place to look for trouble is when you check the bleeder screws on the calipers. Make sure that all of your bleeder screws can be loosened. If you have a bleeder screw that won't loosen, or worse yet-one that breaks off-start checking the balance on your VISA card. A frozen, or broken, bleeder screw means you're going to purchase a new caliper. I've heard of all the various ways of removing obstinate bleeder screw and I don't like any of them. Just go out and get a new caliper.

I've now got $70.00 worth of wrenches to install a $119.00 genuine-GM master cylinder. It takes the average Corvette shop less than a 30 minutes to install a master cylinder. And as I said, they'll bill you for an hour of labor. Labor charges are now around $70.00 an hour for Corvettes so I'm already in the hole on this job. Then again, this is supposed to be a hobby-right?

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