"load sense valve" is this the same as the bias valve/Brake pressure regulator? If so, using my poor explanation above, which way would be deemed loaded/open?
OK, I personally arn't familiar with the specific set up on the Mk2 (but maybe some of the other Mk2 regulars can confirm).
However, on all cars, irrespective of make/model/type - they have to have a way of limiting or reducing the hydraulic pressure to the rear brakes. On a non-ABS car, this is usually done in one of two ways. The simplest and cheapest method (so that is what Fqrd used
) has a simple 'fixed rate' pressure limiting valve - so when a certain fixed pressure was reached, no more increase in pressure was applied to the rears, even if Arnie pressed the brake pedal with all his might.
The second method uses an 'adjustable' valve which can vary the pressure in the rears, dependent on vehicle loading.
The best way to manually identify which you have, is to simply follow the metal brake pipes from the rear wheel, under the car. If the pipes pass through a fixed metal piece (which looks like just a large pipe union) - there may be two if your brake circuit is diagonally split - and then goes toward the front master cylinder - then that is the first type (the fixed rate pressure limiting valve) - and there is nothing you need to do with these.
However, if the valve appears to have a metal 'arm' coming out of it - which looks like it could move, then that is probably a variable rate load sense valve. The main body of the valve should be bolted directly to the floor pan (or other object which doesn't move), and the end of the rod will be linked to a suspension arm, or the rear suspension beam. If you have one of these, then unhook then end of the rod, and temporarily 'wedge' the arm upwards, as though mimicing the suspension when fully compressed (as though you had 20 bags of cement in your boot). A couple of warnings though - don't leave the wedge in once you have finished the bleeding, cause if you do, and drive with it there, the first time you hit the brakes, the back end is likely to overtake your front end. And the other warning is that these are prone to seizing up. So if you bend the arm, but there appears to be little or no movement in the actuating pistion in the valve, then consider replacing it.
I've also read that when using the 2 man method, pushing the pedal as far as it will go can burst the seals, or something to that effect, not sure what seals; caliper, master cylinder, who knows, is it worth putting an object between the pedal and floor of the car to stop the full travel of the pedal? I guess potentially this will ever not allow the air to be pushed out of the system so effectively if at all?
Hmmmmm. Yes, I agree that if the master cylinder is worn, then using the full pedal stroke
may tear one of the seals. However, if this were to happen, I would honestly be thankful that it let go whilst you were bleeding - rather than getting sudden and unexpected brake failure the next time someone steps out into the road. This would only affect the seals in the master cylinder, and not the caliper or wheel cylinder seals.
And using a block under the pedal wont work. Because on braking systems which use 'dual circuits', then the master cylinder has two 'tandem' pistons. So when one circuit is being bled, one of the pistons hardly moves, and the other one travels along its full length (which should be just half the total travel). And when you bleed the oposite circuit, the opposite happens with the pistons in the master cylinder. So you really cant help but to use the full stroke.
HTH
