Driver's side rear wheel leaking brake fluid and has a rattling noise. what could this be?

Time for shocks and struts.

Brake lines by rear door on drivers side are a common failure point. lines under door failing can cause a total brake failure. Just replace and bleed the lines.

AT FIRST GLANCE I WOULD BE LOOKING @ BRAKE FLUID CHECK LEVAL AND REAR WHEEL CYLNDERS MAY BE LEAKING, OR MASTER CYLNDER BYPASSING

Hi Chris, The brake system is basically very simple. If you have duel braking on your vehicle, the usual method is having two brakes operate on the front with for example the left rear and the other system will also operate two front and the right rear. This type of system will have two calipers on each of the front wheels. The tandem system works in a slightly different way, having the forward part of the cylinder pressurizing the rear brakes and the rear part of the cylinder pressurizing the front. I think under the circumstances you are describing, I would have a friend sit inside and pump the brakes repeatedly until the system becomes pressurized (maybe twenty thirty times of pumping the brake pedal) and then ask him or her to keep it pushed firmly down until you find out where its leaking. The amount of brake fluid you report having been sed would indecate a severe leakage. Check the lower parts of the rear wheels for signs of leaking wheel cylinders and then dito for the front wheels. Any signs of wetness at these areas and along the brake system (the plumbing or pipe work) will indicate where the leakage is. If you cannot identify a wheel which is leaking, carefully inspect around and blow the master cylinder and if this no sign go along the fluid lines, taking special note of where the damaged pipe was repaired. If there is a blockage in the line, air may be trapped at that point causing difficulty in pressurizing. Once the place of leakage has been identified it must be attended to before bleeding the system. When bleeding, begin with the wheel furthest from the master cylinder, and work your way back to the master cylinder one wheel at a time, until you reach the closest.Keep in mind that you may find it required to pump the pedal many many times before opening the bleed nipple.Regards John

replace the brake hub

is the fluid coming from the tire or from the backing plate of the brakes if it is from the backing plate of the brakes then if you have drum brakes its safe to say your wheel cylinder is leaking

You should look at your rear brakes. The leaking fluid is likely caused by a bad wheel cylinder. The loud noise could have been some of the brake hardware falling out of place causing your wheel cylinders to bleed, which in turn caused your brake system to be without fluid, which caused you to have no brakes.
If you would like to do this on your own proceed: You will need to inspect the rear brake hardware, shoes and wheel cylinders.
Tools: brake spring pliers, brake shoe retaining clip spring tool, screwdriver, sockets, line wrenches
Step 1 Remove rear tires and drums and inspect brakes.
Step 2 Assess the damage. If you've never replaced brake shoes, you may want to just bring it to a mechanic. If you want to do this on your own continue
Step 3 Take a picture of both sides for reference (don't do this step and you will be kicking yourself)
Step 4 remove all springs, bars, clips (there is one piece that has a star wheel on it, located in between the two shoes near the bottom, try not to rotate this), and shoes
Step 5 if the wheel cylinder is leaking replace it
To install, do the reverse.

It sounds like 1 of 2 problems but to start with jack up the drivers side rear of car and block front wheels with 2 blocks of wood or 2 bricks , put a stand under chassis and then your safe to work.
Release hand brake and spin rear wheels ..and then hold 1 hand bottom and top and try to shake the wheel.. any movement means worn bearings ..any noise when spinning means worn wheel bearings..If ok
get under the car and bang the exhaust all along and if the rattle comes when you get to the muffler you have you answer.
Let me know how you get on . RON

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.

start at the rear wheel on passenger side, then the driver side rear, then bleed the passenger side front then the driver side front, don't let the master run out of fluid, check at least after each wheel, bleed until you don't have air spurting noise and u have a solid stream of brake fluid out the bleeder port, u can buy a brake bleeder wrench from any parts store for a few dollars...