I was replacing the shoes on the rear brakes today and nicked the rubber boot on the wheel cylinder, right next to the piston.

A little bit of fluid (few drops) came out, then stopped...I assume it was break fluid.

I tried to locate a wheel cylinder rebuild kit, but no one in town had one in stock. Everything was two days away. Advanced Auto Parts said the could get me a complete wheel cylinder by tomorrow ($17). This fits into my schedule better so I can get to work on Monday.

When I got home and looked at the repair manual in states to never just replace one wheel cylinder...that you should replace both.

Why is that?

Also, in the interest of time, is there any reason why I can't pull the boot off the new wheel cylinder and replace the torn one? Thus saving me time in bleeding brake lines.

 

Well if I am thinking of what your talking about its just a dust boot to keep junk from getting into the pistons that push out when you apply the brakes, you should be able to just replace the boot IMO. If I miss something someone correct me.

 

First, the boot is just a protector to keep out dirt. The first thing a mechanic does on an inspection for the brakes is pry up the boot to see it its leaking. Your wheel cylinder probably will work fine for a while but get to a point where it will leak enuf fluid to start covering the shoes. THeres rubber cups inside the cylinder that is what is leaking. Its cheaper to just buy new aftermarket cylinders then to try an rebuild them. I would just replace the bad one.

 

This is what I'm talking about...



So this boot does nothing to hold back brake fluid, it is simply a dust cover?

It just caught my attention since a few drops of fluid came out after I nicked it.

I'm off to Colorado on Thursday and don't want my brakes failing as I head down Bear lake Road

 

Yup, just a dust boot. However, finding fluid behind it is indicative of a wheel cylinder that is on the way out. Replace the entire cylinder. I've never heard of a requirement of replacing both. In my over-analness I usually do but it isn't necessary.

 

You have to figure they have both been in the truck the same amount of time. Both have the same amount of brake applications, same old (contaminated?) brake fluid, etc.

Put in both new now, bleed the brakes once and be done with it. As said before, it is a dust seal, but if there is fluid inside of it, it's new cylinder time. Should bleed the brakes every few years anyway to get rid of the fluid that has absorbed moisture (and causes rust pits inside wheel cylinders)