Rear Right Hand Side Brake Not Working

Tiny
HAWX
  • MEMBER
  • 2007 KIA PICANTO
  • 1.1L
  • 4 CYL
  • 2WD
  • MANUAL
  • 93,000 MILES
Hi,

This past Thursday, I brought my car to the Vehicle Testing Station for road worthiness tests but they discovered that my right hand side rear brakes are not working. Results is 0.0 braking compared to the left hand side which is 0.4 which is ok. The emergency brake is fine just the foot brake for the right hand side rear.

I had a mechanic adjust back the brakes and when I went back on Friday for the test, it still failed with 0.0.
I jacked the car up, start the car, had someone press the brakes fully and tried to turn the wheel manually with my hands and to my surprise it still rotated!

Can you please shed some light as to what might be causing this problem?
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Saturday, November 14th, 2015 AT 12:32 AM

6 Replies

Tiny
CARADIODOC
  • EXPERT
This occurs most often when you have rear drum brakes and a wheel cylinder is corroded so the pistons can't move out to apply the shoes.
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Saturday, November 14th, 2015 AT 12:43 AM
Tiny
HAWX
  • MEMBER
Hi,

Yes they are indeed drum brakes. Can the wheel cylinder be dismantled and cleaned or it will have to be replaced?
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Saturday, November 14th, 2015 AT 12:53 AM
Tiny
CARADIODOC
  • EXPERT
Before you take anything apart with the wheel cylinder, try pushing on the shoes or wheel cylinder's pistons to see if they are indeed stuck. You should have to press pretty hard, but you can move the pistons with hard thumb pressure.

In the '80s we always rebuilt them with every brake job. But today new ones are very inexpensive so we just replace them. The ones that get stuck are generally the real small diameter ones that cylinder hones are too big for.

You also have to look at the steel line to see if that soft metal nut is going to come loose. Watch that it doesn't stick to the line and twist it off. Use a flare nut wrench, also called a line wrench. Those grip the nut on four sides instead of two. If the line won't come loose without breaking, you may have to resort to rebuilding the wheel cylinder. Once you have it apart, wash it out, then look inside to see if there are pits or rust spots near the middle. Those will be on the bottom where water settles. If there are pits in it, you have no choice but to replace it. If you don't have a small cylinder hone, or the wheel cylinder is real small, you can put a piece of fine sandpaper through a cotter pin, then stick that in a drill to spin it. Use that to shine up the inside of the cylinder and to clean out any impacted dirt and rust.

If the nut won't spin on the steel line, you can often loosen it a little, then unbolt the wheel cylinder and spin it off that way. You won't have room to do that on some car models.

Don't use penetrating oil on the nut and be extremely careful to not get any petroleum-based contaminants on anything that brake fluid contacts. Engine oil, transmission fluid, power steering fluid, and axle grease will contaminate the brake fluid and make rubber parts swell. The fix for that is REAL expensive. Professionals even wash their hands with soap and water to avoid getting fingerprint grease in there. If you buy a rebuilding kit for the wheel cylinder, when you pop the new lips seals in, lubricate them only with fresh clean brake fluid, nothing else. You can use Brake Assembly Lube, which is just thick brake fluid, but I haven't seen that around for a real long time.
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Saturday, November 14th, 2015 AT 1:19 AM
Tiny
HAWX
  • MEMBER
Hi,

I forgot to add to my previous post. When the car was jacked-up and had someone applied the brakes, the wheel did turn but with some force so could that mean the piston are really corroded?

There is no brake fluid leakage found.
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Saturday, November 14th, 2015 AT 2:25 AM
Tiny
HAWX
  • MEMBER
Hi,

You were right, the wheel cylinder was not working properly. One of the piston had corrosion on it and thus was unable to function properly. After a good clean and light sand paper sure did the trick.

Its now clean as a whistle! Many thanks for your help in identifying the issue.

Kind regards.
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Sunday, November 15th, 2015 AT 8:44 AM
Tiny
CARADIODOC
  • EXPERT
Dandy. Happy to hear it's solved.
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Monday, November 16th, 2015 AT 9:12 AM

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