6 replies to this topic

[maccers]

Can someone who has the above confirm the brake pipe routes from the master cylinder?

Mine is a green tag mounted on a servo, and I just cant bleed them at all, which is really annoying, every single hydraulic part is new, pipes the lot.

I have the bottom or the pipe closest to the servo feeding the front pipe, and the top, or the pipe further away from the servo feeding the rear brakes.

I have read some articles that describe both ways, but want to make sure by asking someone with same setup.

The pipes route into the PWDA on the bulkhead - big nut facing the engine bay.

Cheers,
RIchard.

[tiger99]

There should be a pressure reducing valve, not a PDWA (which does not control pressure but has a switch to activate a warning light if there is a pressure imbalance). The PRV should be mounted with the big nut facing the left of the car, the pressed cover facing the right, and the rear circuit must pass through the end with the nut, not the cover, so the rear circuit is on the left of the car. Obviously the front circuit is on the right. (Left and right from seated driver's viewpoint, not as you face it under the bonnet.) As a check, the rear pipe comes up the bulkhead behind the subframe, towards the centre line of the car, the front brake line comes up from the area of the offside inner wing, and the pipes do not cross.

The forward end of the master cylinder goes to the top left (rear circuit) on the PRV, and the rear end of the master cylinder goes to the top right port on the PRV (front brakes). I checked that in the Rover workshop manual, just to be sure.

I believe that to be correct only for an equal bore master cylinder. If it is a stepped bore cylinder, the smaller bore (forward end) would have to feed the front brakes to get more pressure, but as far as I can tell, you would then not have, or need, a PRV.

Beware, probably 10mm and 12mm unions on master cylinder and 3/8 UNF on PRV. You probably know the dangers of that mixture already.

[1984mini25]

If all the pipe work is new you might need to bleed that before moving to the wheels, or you could be at it at some time. start off with the master, pumping the pedal and cracking the unions off same you would with the bleed nipples. The fronts should bleed up with not much hassle, but the rears you might need to bleed the t section on the rear subframe first.

[jimnali]

If all the pipe work is new you might need to bleed that before moving to the wheels, or you could be at it at some time. start off with the master, pumping the pedal and cracking the unions off same you would with the bleed nipples. The fronts should bleed up with not much hassle, but the rears you might need to bleed the t section on the rear subframe first.

This worked for me too. I started with the connections at the master cylinder, then bled each of the junctions in turn until I had fluid through to the wheel cylinders.

The rear was easier as I forgot to check that the nipple was closed before I filled the master cylinder. I came back the next day to fins a pool of brake fluid under the back of the car!

[maccers]

Just an update to this for future searches etc. The problem seemed to be with the minispares calipers. I was trying to bleed them with new pads against new discs. I removed the pads, slotted in some 8mm ply wood either side of the disc, as in replacing the pads for the ply and then tried. The pistons moved out and compressed the wood, fluid level dropped. All I did was open the bleed nippes (the MS 4 pots only have two, bleed outside first, then inside) and naturally let the fluid come out with some air.

Took the calipers off, used the ply to protect piston and caliper faces, wound the pistons back in with a g-clamp, pads back in, caliper on, pedal very, very firm! I wedged a bit of wood between the seat cross member and pedal as hard as possible to check all joints for drips where I found none, except the caliper bleed nippes "sweating" a bit, hopefully this was just fluid I had not wiped away fully or tiny bits naturally draining from the closed, but half full nipple.

Success at last!

Only problem now I have seen a nice set of 10" wheels!!

[tiger99]

So why do you suppose that it bleeds with plywood spacers as well as pads? Does it suggest that the problem is the volume of air or fluid behind the piston, which is less if they are pushed back fully? Does that suggest that the calipers were originally made for a car with thicker discs?

Just curious as to why it is so, your fix is perfectly good and will probably help a lot of people.

[Dan]

I've had similar troubles with brand new calipers. I have a feeling it's something to do with the assembly grease or fluid used when the caliper is first built coagulating and stiffening up a bit inside the caliper while its sitting on the shelf, particularly if it's been sitting around for a while. As soon as you can get the piston moving, however you do that, it all resolves itself and they bleed through fine. Initially though the pistons won't budge and the fluid won't move through the channels in the caliper at all. I think simply giving at least the piston on the hose connection side a twist will be enough to break the stiction and get everything moving.