I have what appears to be a leaky caliper and a leaky lever, on different brakes, so I want to swap out the leaky bits to make one good brake, then try and sort out the other bits later. But one's an open system, the other is closed. Can I run the closed lever on the open caliper?

Thankyou!

There must be someone out there that knows? I ahve an open and closed lever available, but would have to run the open one upside-down as its for a front brake.

Call Hope?

FWIW – running a reservoir upside down shouldn't be a problem as long as there's no air in it

Need to know exactly what systems you have, closed (C2 and XC4) have a bigger bore than Mini based systems like M4 so will not work properly, but open (O2, E4 and DH4) share the basic master cylinder designs,only differing in the top cap assembly. Not convinced about running it upside down either, i'm not convinced you'd guarantee to get absolutely all the air out.

IIRC you're not supposed to run a closed lever with an open brake caliper. I think bad things may result, such as your brakes locking on suddenly on a DH.

It's a C2 and an M4, the replacement for the E4 that was actually identical. What your'e saying is the closed lever won't push enough fluid for the M4?

I don't think running the front brake open lever on the back brake will work because the Open system is almost impossible to get all the air out of the reservoir. If it's upside down the air will rise to the top and be pumped through the system.

I got to the bottom of the problem now, at least one piston seal is blown, but also the lever isn't pumping fluid at all. I'm ok sorting the calipers and I think I know how to disassemble the lever, but could do with advice on whats wrong with the master cylinder and what I need to replace to get it working again?

Cheers

If the lever you use has no room to accomodate the expanding brake fluid as the caliper gets hot it is possible the brake will lock on!
I'd ring Hope to verify compatabilty.
Exploded diagrams of the master cylinders are at the bottom of this page http://www.hopegb.com/page_mep_force_4.html
Its normally just the seals that need changing.

There must be someone out there that knows? I ahve an open and closed lever available, but would have to run the open one upside-down as its for a front brake.

The Sport and Pro closed levers weren't handed. You could rotate the cylinders to suit either side. I think the open ones were the same. Just to clarify. open do not have on the fly pad adjustment, closed do.

M4 isn't compatible with C2/XC4closed calipers. You need a Mini lever. BTW XC4 were rubbish calipers.

Get a seal kit and try rebuilding your set. This may solve the problem. If you see pitting where the piston seal beds in the caliper body, you'll need a new caliper half.

My advice is to call Hope! They have THE BEST after sales support you could ever imagine! Those guys are SO helpful – just try them. I have been tinkering around with Hope brakes for ten years now – great products if you get the correct brake for the application and then look after them.

In your case the C2 lever will push too much fluid for an M4 caliper causing a very hard lever and will require a hell of an effort to generate decent stopping power(kind of like trying to start off in a 44-11 gear ratio).
An open lever won't work with a closed caliper as the caliper pistons have return springs, the closed system maintaining pressure to stop the pistons retracting away from the disc, without this pressure it's constantly like the very first pull of the lever after fitting new pads, where you have the lever come to the bars until the pads close up to the disc.
Despite using the same pads, E4 and M4 were also different calipers, the E4 having larger pistons(same as DH4?).
As for the master cylinder, could be scored bores, main seal worn/scored or split or maybe(and fairly unusual)an air lock in the bore.