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  #1  
Old 08-10-2013, 01:03 AM
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Default Brake Fail

I noticed smoke coming from the brake light switch that is threaded to the power brake booster. I unplugged the two wires going to the switch and the lights went out. The brake lights were on since yesterday and had drained my battery. There is no oil puddles underneath. The reservoir is full. The brake pedal returns to the top position very slowly with the car running or off. It makes a squeaking sound. The pedal is stiff but travels to the floor with the car off and soft and spongy with the car running. I am wondering if the brake booster has failed. I'm not sure where to start. Thanks to all that reply.

Rob
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Old 08-10-2013, 04:49 AM
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These switches commonly fail. Check out rockauto.com...
1962 FORD THUNDERBIRD 6.4L 390cid V8 : Electrical-Switch & Relay : Brake Light Switch
AIRTEX / WELLS Part # 3D5
Price US$2.65/each

I'm sure most of the auto parts stores around your area will have them (or can get them in a day or so).

These switches have a pipe thread and they unscrew. You can do it yourself or bring the new part to a mechanic.
BTW, keep the wires far away from ground or it might blow a fuse. - Dave
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Old 08-10-2013, 09:41 AM
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I am thinking that the switch done its job and kept the lights on because the brake booster failed. The switch is probably gone now from heating up due to the battery drain.
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Old 08-10-2013, 12:00 PM
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I would first take the master cylinder off and see if you have any fluid in the booster. A spongy pedal usually indicates a master cylinder leak. Even though the master cylinder is full even a small leak can cause air to go past the seals.

John
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Old 08-10-2013, 04:50 PM
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Brake boosters fail in a few ways:
Usually the brake pedal gets hard to push or it leaks vacuum (you can hear vacuum leaking when you pull the M/C).

If brake fluid fills the booster, you have two problems. The M/C is leaking and the booster is leaking.

Do John's suggestion. If everything looks ok, clean off everything, replace your switch and bleed the brake lines.

If you troubleshoot from that point, the problem may be more evident.
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Old 08-10-2013, 08:26 PM
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Can the switch failing cause the brakes to fade and be spongy? I thought that the brake booster may be the problem and the switch was activated and stayed on because of it. And it was the brake lights staying on that drained the battery.

Also the brake light switch is threaded into the front bottom of the brake booster instead of how the manual shows it to be on top of the master brake reservoir. What year could these parts be from?
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Old 08-11-2013, 12:32 AM
shafe shafe is offline
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Question booster ?

Can the booster be bypassed? The a.c. and all ac components were removed years ago...booster is bad and under dash, can I bypass?
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Old 08-11-2013, 12:12 PM
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Quote:
Originally Posted by shafe View Post
Can the booster be bypassed? The a.c. and all ac components were removed years ago...booster is bad and under dash, can I bypass?
The booster can be bypassed by plugging the vacuum line at the intake manifold. You will then have basically manual brakes.

John
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Old 08-11-2013, 04:06 PM
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Quote:
Originally Posted by flyinthermals View Post
I noticed smoke coming from the brake light switch that is threaded to the power brake booster...
Quote:
Originally Posted by flyinthermals View Post
...Also the brake light switch is threaded into the front bottom of the brake booster instead of how the manual shows it to be on top of the master brake reservoir...
Now that I've read this twice, it must be for real. I've just never seen a setup like that. Can you show a picture of your booster and brake switch?

Here is a stock brake switch:


The only other setup I am familiar with is a mechanical brake switch, mounted at the brake pedal support. I am still wondering how on earth your brake light switch could work off of vacuum. I gotta see this... - Dave
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Old 08-11-2013, 07:49 PM
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I was mistaken. The switch is where it should be. I was thinking of something else. I hope the fix is as easy as installing a new switch. The brakes seem a little spongy and return to the top very slowly???
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