Fourdogs

I have to replace my rear brake light switch. What tools (size socket) are needed. Also will I loose much brake fluid when replacing?

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glider

Not a difficult thing to do. Some are hex head and others are like an oil pressure sending switch so you need a different socket.

You may have to bleed because there is no way to swap them without introducing air into the system. As long as the cover is on the master cylinder, you'll only get a few drops out of it.

Breeze3at

I just measured my '07 FLHTC switch, it's 17 mm hex. My '92 Dyna switch is the odd shape, a 26mm or 1" SIX point socket fits it. A deep well works best.
Glider covered you on brake fluid. I also fill up the new switch (few drops really), just to minimize the air factor. Most runs out, but it makes me feel like I tried.

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HKSkully

If you depress the brake pedal slightly, the master cyclinder port will be covered up by the the piston movement and you will only loose very little fluid. Just be carefull because when you break open the hydraulic system, it will initially be under a slight pressure. This will keep your master cyclinder from gravity bleeding dry.

Hoople

I may be wrong but I would think having the master cylinder gravity drain would allow less of a chance of air getting into the system while you swap out the switch. I would actually have a helper push on the pedal very slowly to create positive fluid flow thereby preventing air from being pulled in.

Yes, no , maybe?

Bud White

either way your gonna have to bleed its gonna get some air in it

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glider

Seems logical to me.

Jack Klarich

Very good way to keep air out of system, have used this way before, steady pressure not too much

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rlb333333

you'll need a sendingunit socket and rachet,,hex wrenches,,you wont loose much brk fluid ,,but will need to bleed system,,i recomend puting a length of vacuum line in a plastic bottle w/brk fluid in the bottle and bleed system,keep resivour topped off at all times,,piece of cake ..or if you have a reverse bleeder ,,even easier..

good luck

Dr.Evil

It's not a bad job to bleed the brakes, not like a car. Only a couple of oz of fluid and you will have nice new fluid in the system. Did it myself, and I am only 5'6"