Brake master cylinder

for the past three or four weeks have had the ABS light coming on intermittently and some times the parking light as well on my 1996 windstar
filled up Master Cylinder and problem stopped for a couple of days
the fluid was disappearing no evident leaks mechanic assumed it was the master cylinder itself and leaking into Booster
had it replaced today but while they were repacing it they found the Cruise control switch sensor valve on the bottom front of the Cylinder Was defective
could the fluid have been escaping from this or is the problem unrelated
I hate to think that I replaced the master cylinder for nothing when the problem was a $22 sensor
Anyone know if a defective sensor will cause fluid to dissapear
thanks
roger

yes, the sensor can/will leak.

I have the same problem (stil is leaking, I will fix it tomorrow) , the leaking is coming from the sensor under the master cilinder, but it took me a while to find out the source of the leak. It is a shame that we can not place pictures in this forum to show you the leaking sensor. Thank you for the advise, I will replace this sensor. (if you want the picture, send me a message).

Jaime