Rear brake cylinder not pushing fliuds - 2004 Suzuki RM 250

I am not sure what kind of vehicle we are talking about. not all rear calipers have a screw type piston. to take a stab in the dark at your problem as far as lining up the caliper when reinstalling the bolts get both bolts started before tightening. If your problem is fitting the new pads and caliper over the rotary it would be necessary to push the piston further back into the caliper. if it is a screw type or just requires you to push it back always push or screw it back all the way till it bottoms out after installation it will take a couple pumps of the brake pedal to set everything back to specs. FYI when pushing the caliper back I do not like clamping the hose or backing off the bleeder screw to me it leaves to much room for erorr. i prefer to pop the master cylinder cap off and then just lay it on there then begain to back the pistons up that way there is no fliud loss nor a chance for air to breach the system. good luck friend.

As you didn't explain which fluid is low, here's a general explaination. There's always a cause for any fliud being low, the only fliuds that can fall below minimun levels are brake fliud [ as the brake pads or shoes wear it takes more fluid to push the surfaces together ] if not checked on a routine service, such as oil changes. The other is windshield washer fliud, which is lost with use.
Any other fliud loss isn't normal, and should be addressed.

Replace the broken line then, you must bleed the entire brake system , each wheel works by itself on these cars, . Put the rearend in the air get the tires off and then find where the lines go into the ABS unit. Bleed fliud there first, then the individual wheel cylinders in the rear. after you bleed the system, check to make sure the brake system is balanced.

very scary, but first you would need to see how much brake fliud is in the resv. how low are the pads,but that probably wont be the problem. easy way to check is with the car in part and running, press down on the padel to see it will stay at one point when depressed. if it holds but slowly lowers it might be a sign of a leak at one or more brake lines or a bad master cylinder

Normally when the brake pedal goes almos to the floor it is an indication of low brake fluid. Low brake fluid is an indication that front and/or rear brakes are wearing. As the brake pads wear down more brake fluid will be required in the wheel cylinders or calipers. Hint, the front brakes usually wear much faster than the rear due to the fact that the fronts due a much greater braking function that the rear. Check the front pads. Don't let them get down to the metal scraping metal stage before you change them out. This causes unnessary damage to the rotors. Look at your master cylinder on the firewall under the hood in front of the steering wheel. If the fluid level is belowhte "max" mark add fluid. Low fliud should also show as a red "brake" light on your dash, but not always.

use a C clamp or a very large pair of channel loc pliers

Just us a c-clamp to push the piston in but before you start turning the clamp open the bleeder screw to allow the fliud to drain instead of pushing dirty fluid back into the system

Is the fliud a lite clear brown/tan (brake fliud) or is it a dark black colour (gear oil)? It sounds like you have a brake fluid leak. Check your steel line on the rear axle and then remove the wheel and drum and check the wheel cylinder. Top up your Master cylinder and bleed the brakes. You might find the light scrubbing noise gone.

if you can see a good amount of wet brake fluid between the brake master cylinder and the brake booster. and you have been adding fliud often,you could have a bad master cylinder. it has to be replaced not rebuilt. you however may have a far more common problem, a rusted through brake line.have someone pump the brake pedal, than look under the car for a brake fluid leak ,repair as needed. than bleed the brakes for a good hard brake pedal
good luck chris