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MG TD TF 1500 - Brake lights stay on!

The brake lights on my '53 TD stay on all the time. I adjusted the brake pedal to eliminate some excessive play and now they stay on when the ignition is on. I backed off the adjustment to where it was before I worked on it and they still stay lit. The car has sat for 21 years until I bought it a month ago. I don't recall the lites staying on when I got it but then I never checked either. The archives seem to deal with switches that don't work. I can't find any notes in there to indicate that the switch is bad. For the price of a NAPA switch it is worth the test unless someone can set me straight.

Mark Strang

Hi Mark,
see "tail light mystery" 5 Sept on this board.
Ray TF 2884
Ray Lee


I simply got a NAPA SL144 switch which has threaded terminals, removed the old unit, installed the new unit, and all seems to be okay. Now, if I could just get the red ignition light to go off instead of staying on all of the time. I'll work on that next. After sitting for 21 years, I'm suprised that more little things aren't wrong.

Thanks for the tip.

Mark Strang

OK after all brake lines - shoes Cylinders and flex lines were installed as new, We have been plagued with the stop lights staying on. I rebuilt the MC.
They would come on after a few stops and go out later.

Today I was working on the car for an upcoming club event.
I move the car by hand in and out instead of starting it up for a few feet( not to bring up getting my 6'4" into and out of the car ).
anyway.. I pushed the car back into the garage and pulled the parking brake. Just before pulling the brake, I saw the lights on again but when I pulled the brake, they went out. HUMMMM ! . Let the brake off - lights on - Pull the brakes - lights off.
This is confusing me.
Has to be in the rear brakes some how..
Can anyone shed any light on this problem?

M Grogan

Have you double checked the assembly of the master cylinder? If residual pressure stays in the line/system after you release the brake peddle you could have the brake light stay on.
From my recollections the dishes washer has to go in the right way round.
Just a thought.
You could try opening a bleed nipple and see if the light goes out instantly. As a check.

R D Jones - Ex Pat

ROD, thanks But I was not in the car and never stepped on the pedal. I was pushing the car and reached in to pull the parking brake when I saw the lights on( I did have the key on as I was warming up the engine.)

Pull the parking brake = stop lights off.

Releasing the parking brake = lights on.

All without touching the pedal or using the MC.
M Grogan

I have had very poor luck with the common auto parts store hydraulic brake switch on a number of my cars, although the usual failure mode is the lights will not come on at all. I finally paid more money and fitted the low pressure switch available from Ron Francis Wiring. These have the additional advantage of coming on at very small movement of the brake pedal.
John Quilter

Mark and M Grogan - I suspect that the relieve hole in your master cylinder is clogged or the pedal is not allowing the master cylinder shuttle is going back far enough to uncover the relief hole. It seems to me that I remember that some of the master cylinders had the relief hole was not properly positioned.

M. Grogan - I also suspect that the brake lights going out when you apply the parking brake is the result of the pressure of the rear shoes against the wheel cylinders is being relieved as the result of the shoes being pushed away from the piston in the wheel cylinders. Cheers - Dave
DW DuBois

Dave -

If Mark and M Grogan opened and closed one of the bleeder valves to relieve the pressure, would the lights go off?

LM Cook

Since the brake light switch is turned on by hydraulic pressure, I would expect that it would. Cheers - Dave
DW DuBois

Mark - Just though of the possible problem. Check the draft excluder around the brake and clutch pedals, that it is pushed down as far as possible on the pedals. If the excluder is riding up on the pedal shafts, it can prevent the brake pedal from going all the way back as it should. Cheers - Dave
DW DuBois

This thread was discussed between 06/09/2012 and 12/11/2016

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