John,
I've never had a problem exactly like yours but......
Consider when you fit a new set of brake pads. You lever back the pistons to allow room for the new pads. This leaves the new pads just a few mm from the disc. Then you get in the car and pump the pedal to bring the pads into contact with the discs.
Amazingly the pedal may go to the floor a couple of times before it goes firm again.
This can be a major shortcoming with a conventional braking system* if there is a fault......that one full stroke of the master cylinder actually moves the parts at the business end a very small distance.
It is easily possible to get in a muddle with old Land Rover brakes where the first full stroke of the pedal moves the brake cylinders out to the drums but it takes a second push to get a firm pedal and some braking action.
Just a long shot but I wonder if one of your brakes "stuck" too far in the off position so it took the full pedal travel and still nothing happened, then the second pump you gave it brought things back to normal.
A long shot?
*I refer to a conventional system because the fully powered system as fitted to Citroen Xantias and the like will still give you serious brake effort even with fluid pouring from a damaged pipe. The brake pedal just opens a high pressure valve and the system will work under fault conditions until it runs out of fluid, that in itself has a huge capacity besides a normal brake system.
David
|
Building on this, presumably if a caliper had siezed in the "off" position while not being used, and with the limited mileage of this car, I guess thats not impossible, then the symptons could have occured if that cylinder finally freed itself up and began its trek towards the disk ???
Mark (trying to give techie car answers is not easy)
|
Mark(Brazil),
A seized caliper would probably lead to noticeable brake imbalance, I'd thought of a seized wheel cylinder piston 'popping out' to meet it's shoe, but this wouldn't lead to a total brake failure, unless it happened on both sides at the same time. (assuming a diagonally split circuit). John says that the brakes have been checked and found to be OK.
Steve
|
|
|
|
Thank you all for the information. I believe I know the cause but I wanted to see if many others had suffered the same trauma, or if maybe I'm the only one to have experienced it (and lived to tell the tale!)? I have on reliable authority that the seal on the Master Cylinder reverses itself when the brake cylinder rod has been machined off-centre. So you get this sudden and catastrophic brake failure, then 5 minutes later everything is as right as rain!
I've also heard, and this also from a reliable source, that Sherpa vans a few years ago also suffered from the same disease. Ring any bells with anyone?
Thanks, John.
|
John,
Haven't heard of this on your car but it was much talked about a while back on Astras. If you levered the brake pistons back quickly when changing pads, and without releasing a bleed nipple, then the master cylinder seals could reverse and the pedal action would be terrible.
Also I do now remember a ZX in the other month with a mysterious feel to the pedal and intermittant excessive travel. This didn't give me a 100% direction for a repair but a new master cylinder cured that.
David
|
|
|
|
|
