[AndyM]

So I have read that when bleeding the brakes, I need to put something in place of the brake light warning switch to keep the piston centered.

Why? Why doesn't the switch keep it centered?

Do i need to purchase this tool?

I'm replacing the lines and rebuilding the valve since the car sat without any fluid for who knows how long before I got it so i want to do it right.

 

[sah62]

The post on the switch doesn't normally touch the piston when the piston is centered. If it did, your dash light would be lit. With nothing touching the piston there's nothing to hold it in place. The tool you're describing uses a longer post to touch the piston and hold it in place.

No, you don't need the tool. If the piston moves it can be re-centered by bleeding fluid. I have instructions posted here:

http://www.musclecarresearch.com/faq

Look for the "My brake system warning light is on. Why?" question.

 

[1969XR7Vert]

Andy,

The shuttle in the block slides back and forth, it slides toward the side that has less pressure (when one side is being bled for instance). The switch is a little metal plunger that connects two contacts (at least on 69/70, cannot speak to other years) when the shuttle moves off center. This is the way the switch works, the plunger moves, so it will not hold the shuttle centered. Here is a tool for this job (or if you are crafty you might make something similar).

Regards,

Bob

 

[AndyM]

Thank you gentlemen. As always, thanks for taking the time to teach. I will be ordering both toninght.