View Full Version : Brake Warning Switch Assembly

03-01-2010, 10:21 AM
I helped a friend of mine rebuild the brakes on his MGB recently. All of the top end hydraulics are the same as the late model Spridgets. Now the brake warning switch assembly is leaking like a sieve. I dismantled it and checked the seals and bore before bleeding the brakes, and everything looked fine, but still it leaks like crazy through the switch hole.

Any suggestions on how to address this problem?

03-01-2010, 12:23 PM
Not sure about what was on late model Spridgets and MGBs but some of the early 1970s PDWAs had two pistons inside instead of one. The intent was that each piston had its own seal that could be inserted from its own end of the housing and NOT have to pass a seal over the crossdrilled hole for the switch. The crossdrilled switch hole can shave/skive the o-ring as it passes through the bore. If your PDWA has a single piston inserted from one end, take a close look at its seals to see if there is a minute cut or shaved area from the switch hole.

It also should go without saying that you need to use the "right" seal material for brake fluid. The common brake fluid compatible seal material is EPDM. If you used regular Buna-N o-ring seals they will be OK with DOT-5 fluid but fail quickly with DOT-3 or DOT-4... and probably with DOT-5.1

03-01-2010, 05:32 PM
broke mine yesterday putting the engine back in.

03-01-2010, 05:38 PM
I'm betting BillM still has it on his 79 that he's parting out...send him a PM.

03-01-2010, 07:24 PM
I do and it LOOKS like it is in good shape.
PM if you need one. ($10.00 plus shipping)

03-01-2010, 10:38 PM
What's the deal w/ your car? It sounds like four bolts and a dowel and you have a driver.

03-02-2010, 06:26 PM
Yeah but between breaking the engine and now I have pretty much parted almost all of the car out. Not worth trying to collect all of the parts now, besides my step-daughter's dad really doesn't want her driving a dark colored, small potentially unreliable car for her first year of driving. He is buying her a newer Cobalt or some such which I will agree is a good bit safer!

03-02-2010, 07:46 PM
my step-daughter's dad really doesn't want her driving a dark colored, small potentially unreliable car for her first year of driving.

That's different than my situation. Our project Spitfire will be the local driver for my older son later this spring and summer. I want him to develop a sense of how cars work and LBCs generally are cars at their most basic. My hope is that when it does break down (and I know it will) that I can walk him through how to get it going again to at least limp home. Though this is very sexist of me... if I had a daughter I might think differently about it.

03-02-2010, 10:36 PM
I am going to teach my daughter how to be situationally aware. Then I am going to teach her how to disarm a man, knock him to the ground, dislocate his shoulder, break his wrist, and get out of just about any hold he can put on her. Then I will teach her how to fix her car on the side of the road.

That is if I can teach her anything at all... she doesn't much car for being taught. :rolleyes:

03-02-2010, 10:46 PM
Hey Bill, still got motor pieces? I need the front rail oil pan rail piece under main #1, front side marker lens and a few other things.

03-02-2010, 11:03 PM
Make a list and I will start stuffing a box.