Brake System Pressure Valve Switch Leaking 1973 B

This B has the dual line braking system without the servo. I am just getting this car back on the road and I suspect this problem is what put the car in the previous owners driveway for over 2 years. The brake fluid leaks out of the pressure switch, thru the centre of the switch, not around the threads. To bleed the system I removed the leaking switch, threaded in a bolt to seal the pressure valve assembly, and ordered a new pressure switch from Moss. The system bled nicely and I inspected fronts and backs and they have been very recently overhauled and look excellent. I got the new switch and put it in place of the bolt, but when pressure was applied to the pedal, the fluid started coming out the centre of this new switch as well. Is this another bad switch, or is the snap-on cap supposed to keep this valve sealed ( I can't see that being so, but you never know ). Anyone shed any light on this leaking?

It's not the switch itself. That is not designed to hold back fluid. It's the internal seals around the little valve in the body of the assembly. The kit for that is under $10, as I recall. You have to unscrew the lines from that body and disassemble it on your work bench and replace the little valve and seals (there are two sizes in the kit, depending on what yours uses). That's where the leak is. Other than having to re-bleed your brakes it's not too difficult a job.

Bleeding your brakes is the easy part. Repainting the inner fender is the tough part.

For what it's worth, take the switch out, and put your bolt back in. Those fail warning lights are a joke any way. I'll bet out of 100 MG there aren't more than one that the light still works. When I have one come into the shop with that problem. I put the switch in the round file and put a bolt with a copper washer in it's place. You'll find out why if you take that assy. off to rebuild it.

Hey... my switch does't work but my light does...when ever someone asks me what its for I tell them its a brake check swith and press it I say as long as the red light doesn't come on we are okay. You should see the looks i get when the light comes on.