1939 Plymouth

[Richard Cope]

My brake light  sending switch went out.  Tail lights work, however brake lights  aren't.  Connect the two wired at the switch and  brake lights light up.   When I unscrew the switch from the brake line, is there any precautions have to be taken?  Will brake fluid come our as long as the brake pedal is not depressed.  Appreciate your help

 

Regards,

 

Richard C

[Mark D]

Unscrew the old and screw in the new, at least that’s all I did. Fluid is not under pressure with no feet on the pedal. Fluid loss should be minimal.

[Richard Cope]

Great Thanks

Rich

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[Sharps40]

Tie the pedal in the up position and change out the switch. Bleed the brakes post switch replacement just to be sure. 

Edited May 2, 2018 by Sharps40
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[dpollo]

because of the switch location, any air will soon work its way back up through the master cylinder.

[Sharps40]

Bleed it is always the best option when the break system is opened. 

[greg g]

I have changed a half dozen hydraulic switches from motor cycles, to foreign and domestic cars and trucks and never needed to bleed any of them.  This is a personal experience observation. Your situation might not yeild the same results.

[austinsailor]

On 5/2/2018 at 5:21 PM, Sharps40 said:

Tie the pedal in the up position and change out the switch. Bleed the brakes post switch replacement just to be sure. 

 

Why tie it up?

[Richard Cope]

Appreciate everyone help, changed the switch out and working fine now.  Tried bleading, however no air in lines.  For the small size and how easy it is to change out, going to start carrying an extra.   

Rich C.

[Don Coatney]

15 minutes ago, austinsailor said:

 

Why tie it up?

Good question. I do not understand the need to tie the pedal up.

[Wiggo]

1 minute ago, Don Coatney said:

Good question. I do not understand the need to tie the pedal up.

Nothing wrong with a little bondage. Don't knock it till you've tried it...

[busycoupe]

25 minutes ago, austinsailor said:

 

Why tie it up?

It may not make much difference with the master cylinder under the floor, but when working on brakes on cars with hanging pedals the weight of the pedal can can force a little fluid out of the open system.

[Sharps40]

On May 4, 2018 at 3:43 PM, busycoupe said:

It may not make much difference with the master cylinder under the floor, but when working on brakes on cars with hanging pedals the weight of the pedal can can force a little fluid out of the open system.

Yep.   Can happen with under floor master too.    OP.   Good job bleeding it.   Always best to do so when the system is opened.    Helps keep ya from failures later. Glad it worked out.