3 replies to this topic

[087dave]

Hi all

If u replace a brake light switch in a 1975 car (the switch is a hydraulic one)
Do u have to bleed the brakes?

Cheers

[KernowCooper]

Anytime you break open a hydraulic fitting there is air replacing what comes out, so best to bleed the system to be sure

[dklawson]

Yes and no. 

 

As Kernow said, you are supposed to bleed the brakes anytime you open a line.  However, with the hydraulic switch, as soon as you take it out, fluid typically starts leaking out of the open fitting.  Therefore, it is not uncommon for people to work quickly to simply put the new switch in place and often find the pedal is still firm as there was no air introduced into the system.

[jcslocum]

To minimize the leakage, put some clear food wrap (Saran Wrap here) under the master cylinder Rez cap and tighten it down. This will block the vent in the cap and let very little fluid out. Work quick and use a new copper seal. Cleanup the area very well with at least water as brake fluid is bad of paint. If your brake fluid is over 2 years old, you should consider flushing the system.

To minimize the leakage, put some clear food wrap (Saran Wrap here) under the master cylinder Rez cap and tighten it down. This will block the vent in the cap and let very little fluid out. Work quick and use a new copper seal. Cleanup the area very well with at least water as brake fluid is bad for paint. If your brake fluid is over 2 years old, you should consider flushing the system.

Edited by jcslocum, 28 March 2014 - 02:58 AM.