Does anyone have an alternative to the stock Pressure Diff Valve. Mine is buggered up and needs to be replaced. The shuttle valve part of it seems to be old technology.
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quote:The shuttle valve part of it seems to be old technology.
Yea, may be old, but when clean and free of varnish is WILL do its job. For those not clear on this valve, it is designed to block off fluid movement to one side of the Pantera's split brake system should one side have a major leak of fluid. The functional side will still have full pressure that forces the shuttle valve to move and block the normally open passage for the other (now leaking) side.
It can cause a headache when bleeding brakes if it slides and varnish prevents it from popping back over into its normal center position. Mine did this once, but a few firm pedal strokes got it back where it belonged.
It can be removed and just replaced with fittings, but if you're going to remove it to do that, why not just take it apart, clean out the 30 years of varnish and put it back in?
Brake system safety is something nice to have, eh?
Larry
The long brass piece is the shuttle valve. The center detent is for the switch plunger to rest, with the switch normally open. When the valve slides, the switch detent is depressed by the larger diameter of the valve, closing the circuit and turning on the little red light, which on my early 72 is in the dash between the tach and speedo.
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Per a Post dated July 16,002 by forestg.
"This subject has come up before and other have tried to perpetuate the myth that the shuttle valve closes off flow to the siide that loses pressure. I've cut open several of these valves and they all are machined down on the ends so that fluid will pass right on by. Forest".
My problem with mine is that the threads in the port that goes to the rear circuit are stripped. I called Dennis at PP. He said do away with it. Install a standard peddle switch for the brake lights. I am still not clear on how to then set off the red light on the dash. But by the time you see the red light you already know the brakes are gone.
"This subject has come up before and other have tried to perpetuate the myth that the shuttle valve closes off flow to the siide that loses pressure. I've cut open several of these valves and they all are machined down on the ends so that fluid will pass right on by. Forest".
My problem with mine is that the threads in the port that goes to the rear circuit are stripped. I called Dennis at PP. He said do away with it. Install a standard peddle switch for the brake lights. I am still not clear on how to then set off the red light on the dash. But by the time you see the red light you already know the brakes are gone.
ther is a pretty cool block and adjustable proportioning valve and a brake light switch all in one. It’s made by Stainless Steel Brakes and keeps everything in one package.
nazgul
nazgul
I heard about it from the local RaceShop that handles mostly brake stuff. It should be here on Wednesday. Always waiting on Parts. Denver does not have any fully supplied HotRod parts stores.
Better late than never I say.. but was on another forum and found this excerpt from a Ford Service manual on these valves.
Where they say to depress the brake pedal I find that it takes a couple of hard stomps on the pedal.
Forest
Forest
quote:Where they say to depress the brake pedal I find that it takes a couple of hard stomps on the pedal.
That was my experience, also.
Larry
How's Fla treating you Jeff?? If your valve is good maby you could drill it and re-tap it and size it back down. Take the valve in to Napa, I just resized my striped out lr caliper with a repair kit. Taped it (npt threads) installed brass fitting, works great. Still have lousy pedal, maby I have the same problem with my valve. I had good pedal, replaced all rear brake lines, now bled it 20 times, still have air somewhere?? I fixed all the rust on my car finally, and rebuilt lr suspension and new pp radiator. Almost spent 4k? Ouch!