Squealing sound while backing up

I have a 2005 Elantra Hatchback. It makes a squealing sound (from the rear of the vehicle) while backing up my driveway, which has been getting slowly and progressively worse over the past two weeks. It's only when backing up, not going forward, and not when braking.
 
If anyone can shed some light on this, I would be extremely grateful!!

Squealing like "tire squeal" or like "metal-on-metal squeal"?  If it sounds like tires, I would suggest an alignment; if it's metal, it's probably the rear brakes (even if it doesn't do it while braking.... in fact if it changes when you apply the brakes, it suggests they may be involved).

Due to the design of the front-rear proportioning valve on the Elantra, it is not uncommon for the rear brakes to wear out first (unlike most cars that barely use the rear brakes for stopping and the never wear out).  I have 30,000 miles on my own Elantra and the rear disc brake pads are very nearly ready to replace while there is still plenty of thicknes on the fronts.

If you think it's the brakes, you have lots of options.  The Elantra is pretty typical with its brakes; any shop should be able to replace them.  Or you can do it yourself.  If you have the rear discs (hatch back and GT models have rear discs; GLS sedans have rear drums), it's a pretty easy change out but you should know that you can't simply use a clamp to retract the piston; it can't be pushed straight back but needs to be twisted in to be retracted. 

If you want more information about replacing rear brakes yourself, let me know.  Also let me know whether you have rear discs or drums.

It does sound like a metal on metal sound, and from what you said it does sound like my brakes. I popped a tire off and they are disc brakes, and I don't have ABS.
 
I'd like to do the job myself next weekend (6/16) and any tips you could give me (especially about that screw-in piston) would be greatly appreciated. Thanks a lot for responding!

I need to do my rear brakes soon myself, so I've been looking for information.
 
Brake system torque values in lbft:

Master cylinder to booster mounting nut: 6-9
Brake booster mounting nut: 9.6-11.8
Brake booster vacuum hose fitting to surge tank: 11.1-13.3
Bleeder screw: 5.2-11.8
Brake tube flare nut, brake hose: 9.6-12
Caliper guide rod bolt: 16-24
Caliper pin bolt: 26-33
Caliper assembly to knuckle: 48-55
Brake hose to front caliper: 18-22
 
Rear brake components (non-ABS):
 

 
As I mentioned earlier, a tool is required to retract the rear piston. You can't just compress it with a C-clamp; it has to be twisted in. I haven't had to do this yet myself, but I've been told it can be bought for about $10 at most auto parts stores; it's more or less a universal tool. Here is a picture of the tool.


I found these instructions on another forum and removed my wheel and looked things over and it looks like they are pretty good instructions.  This is a long time member of that forum, so I trust that he knows his stuff.
 
REAR DISC BRAKE PAD REPLACEMENT PROCEDURE

Replacing the rear pads is not difficult, but it will take the "special" tool. However, virtually any auto parts store will sell you one for about $10. Some of the larger auto parts stores will "sell" you the tool, and then let you return it if you buy the pads from them. I have made up my own tool for some Honda products in the past, but the slot pattern on our pistons would make it difficult to make your own; and it is not worth bothering with since the real tool is so cheap and effective. For anyone not familiar with this tool: It looks like a small metal cube with four tabs of different shapes on each of the six faces, one set of which exactly fits into the slots on the caliper piston face. Also, in the center of each face is a square 3/8” hole for your 3/8” drive extension that allows you to use your ratchet to rotate the piston.

Expect to find the old pads pretty corroded and stuck in their slots.

Here is the procedure I followed:

1. Jack up entire rear of vehicle and remove the wheels. I have a good floor jack and use the pad that the center rear tow/tie-down hook is welded to as the jack point.

2. Place supports under the rear suspension just inside the rotor dust shields on each side. I used two cement blocks and some short pieces of 2x4” lumber on top of the blocks for a steady, secure support, and then lowered the vehicle until the suspension was again fully depressed. I did this to increase the slack in the parking brake cables to make disconnecting them at the calipers easier. Alternatively, you could just jack up each side and remove the wheels in turn (for those without a floor jack) but I think it is useful to lower the suspension weight onto some good support to increase slack in the parking brake cable. This eliminates the manual’s suggestion to remove the center console inside the vehicle and loosen the parking brake adjusting bolts at that point.

Do the following one side at a time.

WARNING: If you have not done brakes before. DO NOT TOUCH THE BRAKE PEDAL OR PULL UP THE PARKING BRAKE LEVER FROM THIS POINT ON. (Don’t let a child play in the car whenever a brake component is off a rotor!!)

3. Remove the two 14mm caliper retainer/slide bolts and lift off the caliper piston and parking brake assembly. Just be careful not to kink or stress the brake hose. There is sufficient slack in the line to do this. Push the piston assembly aside and rest it on the lower slide bolt (the part with the rubber boot). With this out of the way, you can remove the old pads and clean up the stainless steel slide slots top and bottom. You might find the pads pretty well jammed in there. If you have to pry them out, don’t gouge the disc face with your tool.

4. I used a soft brush and some air (I have a compressor that facilitates this.) and cleaned up the rubber boot area around the piston.

5. TAKE NOTE OF THE POSITION OF THE SLOTS IN THE PISTON FACE at this time. Then, using the special tool, a short extension, and your 3/8" ratchet drive, turn the pistons clockwise as you apply inward pressure. When you finish screwing in the piston, the slots must once again be in that position. There is a protrusion on the back of the metal part of the inside brake pad that sits in the slot on the piston face. If you do not have this aligned properly, you won’t be able to get the caliper assembly back onto the rotor. At this point I had a problem. As I tried to screw in the piston, it rotated pretty easily but did not want to move inward.

(NOTE: The following may not be necessary, but the piston did not seem to move inward until I did it.)

I then unhooked the spring on the parking brake "cam bolt" This is easily done with a pair of pliers or vice-grips. The spring is not very strong. Then I slipped the end of the brake cable off. This takes a bit of careful wiggling, but there is enough slack in the cable to get them off, especially since I had lowered the suspension onto the blocks back at the start of this procedure. I then started turning the piston again and found that it now moved inward. Don’t be surprised at the number of turns it takes to get the piston to start moving inward. Be careful not to damage the rubber boot around the face of the piston. You might have to apply a bit of WD40 to help the boot slip as the piston rotates. Crank it in until the piston face is flush with the rubber boot. That should be deep enough for you to slip the assembly back onto the new pads.

5. After cleaning away corrosion, I tested the fit of the new pads. They went in very, very tightly. I didn’t like that, so I pulled them out, and used my bench grinder to VERY SLIGHTLY smooth the metal ears of the pad. You can use some 120 grit sandpaper to do this manually if you don’t have a grinder. I worked this process in small steps, until the pads slipped in fairly easily, but not so that they were loose. You can apply a VERY, VERY SMALL AMOUNT of high temp grease to the pad “ears” at this step. Do not get grease on the rotors or pad faces.

6. Hook up the parking brake cable end. Reinstall the spring, and then place the caliper back over the pads and install the slide bolts. (The bolts need only about 15 – 20 ft lbs of torque. Don’t muscle them too hard because you can strip them if you gorilla them.) If the caliper assembly doesn’t seem to want to seat back on properly, refer to STEP 4 above. ALSO, if you find that the piston has moved back outward so that it doesn’t want to slide over the two pads and rotor, you probably moved the lever that activates the parking brake cam causing the piston to “self adjust outward.” You will have to screw it back in some more with the tool. I unhooked the spring and cable again to do this, but am not sure if you have to.

7. After the unit is reassembled and back on the rotor, go into the car and depress the brake pedal a couple of times until it feels firm again.

You are done on side #1. Now go do it again on the other side. Good luck! If you now find that the parking brake is too tight, you will have to remove the console to adjust the screws and loosen the brake handle. Mine was fine, so I didn’t have to do that.

Good luck!

Is this proportioning valve design 'flaw' something that can be adjusted?  I own two Elantras, a 05 GLS Hatchback (no ABS) and a 06 Elantra GLS Sedan with ABS.  Both vehicles have 4 wheel disc brakes and are wearing the rear pads excessively.  The 05 only made it 14K miles on the first set of rear pads.  I took it to two different dealers and the second one 'found' that the parking brake cable had what they called an intermittent hang.  Sometimes it would fully release other times it wouldn't.  Not sure if they just guessed if that was the problem and sent me on my way.  At the time, I assumed that it had been fixed (under warranty), until I recently looked at the rear brake pads on my 06.  Rear pads on the 06 are measuring 2/32, fronts 9/32 at 18K leading me to believe the intermittent hang issue is not to blame. 
 
Both vehicles are driven primarily in the city so there's plenty of traffic and stopping.  I just think there's something wrong with having to replace replace brake pads every 15-20K miles on my vehicles regardless if it's the front or rear brakes, but especially the rear.  The rear pads are smaller and are not designed to do the majority of the stopping of these vehicles so why is the proportioning valve designed this way?
 
A few notes....
 
When I encountered this problem the first time with the 05, I received several replies (in another forum) along the lines of "try releasing the parking brake before driving."  That is not the issue here and I'm hoping for more helpful replies than that from this forum.  Thanks in advance!
 
Also, I have yet to check the 05 to see if the rear pads are wearing any diffrenently, but the brake dust still builds up on the rear wheel covers much more than the front, so I have to believe they're still wearing faster.
 
Any info/help/suggestions would be greatly appreciated.  If all else fails, I guess I'll become pretty good at changing the rear pads so thanks for the instructions above Doohickie!