Leyland P76 Owners 2007

Technical

Master Cylinder Switch

by Yowee

Problem:-

The car did not have brakes so I had replaced the existing master cylinder on my car with a swap out unit that I got from another car. Only I found that when I applied the foot brake, the brake oil would flow out of the switch.

How do I fix this:-

To fix this, I replaced the switch with a metal plug, and thought no more about it.
As I worked through the car's problem, I ended up purchasing a new master cylinder.
The need for a switch was apparent in that the new master cylinder did not have one.
Time to figure out what was causing the oil leak, so I hunted around and everytime I had a replacement switch the same thing happened, oil leaded from connector end of the switch. After a number of switches, the penny dropped that I had a problem with the master cylinder not the switch.
Replacing the Master cylinder, pressing the foot pedal no oil came out of the hole, all the switches that I located were perfectly OK.
Excited I put the switch into the hole and did it up firm.

Turning the ignition on the brake light came on, check the hand brake to see if it was released, which it was I had created another problem , so I pulled the wiring off the switch.
Sleeping on this problem it came to me that what had happened was that I had screwed the switch in to far, the plunger of the switch was depressed causing the switch to short out. Backing out the switch the problem would go away.
Using a multimeter I backed out the switch and the readings went from 1 ohm (short) to a meg ohms (open circuit) reading.
Connecting the wiring harness the brake light did not come on.
I adjusted the switch so that the switch plunger did not touch the plunger which works only when either of the oil resevoirs are empty in the master cylinder.

Last updated
Oct, 2007
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