HI I have a1989 chevy p/u c-1500 sometimes backing out of my driveway the rear right tire locks up the wheel cylinders and rear lines are new brake shoes and drums are good I though it was the emergency brake cable but I haven't been using it and still does it sometimes ANY IDEAS ??

No mention if rear drums or disks altho let's assume drums. Look for fluid leaking out of inside of rear wheels it will leave a stain on inside of tires below the drums. Replace 25.00 wheel cylinders 40.00 brake shoes, replace drums for 40 each or have them turned for 10 bucks each, replace hold down spring kit as well as the two lines going to the rear wheel cylinders, they can be broken off first before attempting to remove wheel cylinders this will allow u to get a socket on the fitting going into the T-block located usually to one side or in middle of the axle. Just break the old line off and gently hammer a socket onto old fitting sometimes give quick jolt to tighten prior to trying tonremove fitting to loosen rust. WD40 perpetrating oil and brake fluid is a good release agent but brake fluid is very corrosive like acid and will eat paint and burn eyes and is highly explosive if heated with a torch. If no sign of leakage then check to see if shoes have separated from their position by hold - down springs breaking or the pads separating from the shoes thus the shoes will rub against the drums and make noise like rattling or scraping, and engaging as they seem to be doing here. One other consideration is the abs modulating valve unit located under the hood. A big black flattened football shaped device is the booster the aluminum block attached to the face of this is the Master brake cylinder and is where the brake fluid is refilled. This should be kept at min and max levels and will be low if the rear wheel cylinders are leaking and showing leakage signs as described above. The booster and Master Cylinder is located under hood drivers side firewall below the windshield. Carefully remove the cover to inspect fluid levels. Below or close to this Master Cylinder is the modulator for the abs system. Brake lines will be going to this from the master cylinder then to the wheels, typically one for each front corner and one line to the rear which then separates to each wheel at the T-block mentioned above. Be careful of moving and damaging any rubber flex - hoses as these can be costly but must be repaired if cracked. Be sure to get correct fitting lines as there are inverted and extroverted fittings on the ends and small increments in sizes from metric to standard sizes. Always match old fitting threads by holding next to new ones and see if threads fit exactly against new ones and diameter is same as sometimes bigger diameter will still match threads but will be noticeably bigger. All in all with respect to the description given (better than most I see here) I suspect this modulator control valve unit is the culprit or a short in the wiring leading to it. Inspect all wiring to the abs sensors to each wheel for breaks and solder new wires on fairly easily if broken or exposed and shorted. Try unplugging abs fuse and relay prior to removal of the unit. Your brakes should work normally under these conditions but perhaps with more pressure. Air or problems in the lines or wheels at this point will make the brakes work individually and if a wheel grabs more than others for instance indicates a problem with that wheel or air in the lines of the others or again the modulator proportioning block attached to the master cylinder. Wow! There are tricky processes here but some you may be able to check with relative ease if you read carefully and figure my solutions out, starting with the easiest first and that's fluid levels in master cylinder and leakage at inside of rear wheels. This is a dangerous situation and I don't recommend driving until resolved. This could be a sign of imminent and total brake system failure. Try looking on kijiji for cheap back yard mechanic in your area. www.kijiji.com in USA, www.kijiji.ca in Canada and kijiji is nearly world wide! YouTube.com gives great videos to help you with this solution as well for free. Good luck hope I help some but understandable if frustrated and perplexed but maybe one bit of advice may lead to your cheap solution. East Coast Canada Rocks! !

Fill the master cylinder with brake fluid before beginning. Jack the car up so that the two rear wheels are about six inches above the ground. Slide under the right rear wheel and look at the back of the brake system for a small bleed valve. A bleed valve is a hollow bolt. When loosened it will allow the brake fluid to flow out and result in the vehicle having no brakes Fit a rubber hose over the end of the bleed valve. Make sure it forms a tight seal and make sure the free end is below the level of fresh and clean brake fluid. As the brake fluid in the line pushes out of the system, you will see a bubble come from the end that is under fluid.Have a helper sit in the driver's seat and follow your instructions. Tell your helper to pump the brakes hard a few times. Open the bleeder valve and tell your helper to press the brake pedal firmly down to the floor and hold it there until you indicate otherwise. Close the bleeder valve and have your helper release the brake pedal. Repeat this process until you see a small bubble ejected from the tubing under the surface of the brake fluid in the jar. Once you have finished with this wheel, move to the left rear wheel. Before you begin the next wheel brake, refill the master cylinder reservoir. Get set up and repeat the same steps for this tire.The next two wheels you will bleed are the right front wheel and then the left front wheel. Bleed the wheels in the order of the longest brake line first and then working towards the shortest brake line. Refill the master cylinder reservoir before beginning each new wheel. Once the rear brakes are finished, lower the car and jack up the front of the car. Remember to road test the brakes and make sure they operate well

After you remove the tire, the drim should slide off. If it doesn't then try using a rubber mallet and gently tap on the outside edge as you pull on it. Sometimes you also need to tap on the drum in the center part. I have sprayed penetrating lubes like WD-40 or PB Blaster into the seam at the center. You may also have to back off the parking brake cable or even use the adjuster to back off the shoes.

It sounds like something in the left rear drum is causing it to lock up. It may be contaminated linings, from a leaking wheel cylinder or maybe some broken hardware. You'll have to remove the drum to take a look.

frozen or engaged parking brake cable or possible bad brake hose but that would cause both to lock is the other wheel cylinder leaking? that would releave pressure from the wheel . a fluid leak (axle seal or cylinder) can cause the locking feeling because it slips then catches when the fluid wears off hope this helps

bad master cylinder seal must replace master cylinder

One of the wheel cylinders is leaking, pulling air back into brake system and it's going back to the4 master cylinder. Look for brake fluid leaking at one of the wheel cylinders, that's where the problem is.

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The piston is binding in the wheel brake cylinder, perhaps a bit of rust in the cylinder.
Inspect it, replace wheel brake piston and maybe the cylinder if you can't make it "smooth".

Hello,
I hope this helps.







Thank You,
Roy

Try a clean and adjust on the rear shoes, because sometimes when they aren't properly adjusted they won't seem to work properly. Also there is a common "squishy" petal feeling after brake work on most all larger GM's around that year, wich I have run into several times. Try test driving it, and put a couple miles on it, That usualy helps.
Good luck!