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My dad reported that the brake lights are staying on. I replaced the brake light switch and test drove the car and not trouble and he just reported that the brake lights are staying on again.

Perhaps if the brake lines heat up and the fluid expands the switch could close. I told him to test it and drive the car and when he stops see if the brake lights are on then wait 30 minutes and if the lights go out that defined the problem as being fluid expansion and not wires.

I checked the fluid cap and it vents correctly so that is not it. Sadly the master cylinder and brake plumbing was not one of the items I addressed during the Pampered Packard Spa and Wellness Center visit last summer...I knew I should have dug deeper...

The only thing I can think of is that I used DOT 5 silicone brake fluid but that should not be an issue as silicone does not attack any rubber or metal and it should not expand any more than DOT 3 fluid does.

Are there any nuggets of troubleshooting advice from the wise old Packard owls that dwell behind my keyboard?!?!?

THANKS!!!

Bad brake light switch. Napa carries the replacement. Look in the Parts X-Ref here on the website.

Also, DOT 5 is known for causing this issue with those switches when the are old.

And if you want to still use the DOT 5, several have bypassed the hydraulic and went to an all mechanical switch that completely eliminates the chance of fluid destroying the switch problem. The lever can be bent as needed to touch the arm or some part of linkage. Switch is mounted on the toe plate or frame so it is activated as soon as the pedal is moved.

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Brake lights staying on are almost always from one of these causes: Insufficient free play at the brake pedal. Adjust the pushrod to give 1/4 to 1/2 inch play. Second, compensator port plugged with debris. If you look with a flashlight into the master cylinder reservoir you will see two holes, one large, one small. The forward smaller one is the compensator. Take a little wire and poke it through.

Solving the brake light problem will also solve brake dragging problems.