MG Sports Cars

Funny coincidence... the "Brake" warning light on my wife's Subaru came on this morning. On modern cars like her Subaru, that light is generally triggered by two different switches but NEITHER of them have anything to do with pressure differential between the front and rear circuits. Instead, there's a switch on the brake reservoir to sense low fluid level there. (There's also a switch on the emergency brake lever which warns you you're driving with the parking brake applied. Her iPod had slipped under the lever and was keeping the lever from going down the last 1/4" of its travel.) I wonder which car company was first to realize they could meet the brake light requirement with a switch on the reservoir.

Quote:

...because I don't think that image (above) is a very accurate illustration of how the MG part was made

Curtis,

I believe it's a pretty good illustration, particularly since it was meant only as an explanatory illustration, not a technical drawing. Here's an actual photograph of the device, disassembled:



As you can see, there is no proportioning or metering function involved, just a simple on-off switch, and there is very little movement of the shuttle required before the switch is actuated. The switch is the round white item at the lower right.

There were more than one model of this device offered, but they all were very similar, differing only in minor details. Functionally, they are all identical.

Here's a better drawing, taken directly from the MG shop manual:

You are absolutely right Jim. If you live in Canada and in particular B.C. removing a safety device cancels your insurance. If you should be lucky enough to have an MVI ordered (say for speeding) your car will be removed from the road. Possibly forever.
If you are involved in a crash you would be responsible for all costs incurred by both parties. With ICBC looking for every way out of paying a claim they inspect every vehicle that they can.
Seems like a reasonable risk to me.
Personaly I won't drive a vehicle with a single brake system. The smallest flaw sends the pedal to the floor. With my admittedly aggressive driving style I need the brakes to function well every time. Everything I own has been converted to at least a dual system. And all of the warning systems work.
For the H valve to cause sudden and complete brake failure is a tough one. Both seals would have to fail suddenly and completely at the same time. More likely is the light didn't work (switch, wiring, bulb, fuse?) and one of the brake circuits let go over time. The car was driven this way (yes it can be hard to detect) for some time and finally the compromised valve starts to leak. This shows up as a leak at the switch which is then (sealed, replaced, capped off, epoxied) repaired and all is good until the repair lets go and you have your catastrophic failure.
Replacing the valve and getting the light working is the best repair in my view. The H valve is not a proportioning valve and I don't think that it was refered to as such. The proportioning valve (in conjunction with a combination valve) is just an available upgrade that can be fit in the space that the H valve uses and still retain all of the warning features.
I check my oil and my coolant. Make sure the belts are good and that nothing is leaking. And I am very in tune with my vehicles. Some of them are very high HP and have been known to exceed the speed limit from time to time. I can tell when something is wrong. But I would never start one without an oil and temp guage. So why would I drive away not knowing if my brakes are working?
Fred