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2005 Hyundai Elantra - Fading Brake Pedal

Posted: Tue Aug 28, 2012 9:38 am
by Tim Martin
We got this 05 Elantra that came in. The complaint is a low and fading brake pedal when the brakes are first applied. If you reapply the pedal then it is much better and if you reapply the pedal again it barely has much pedal travel and you have real good brakes. The car has 4 wheel disc brakes so there would be no brake shoe adjustment. We are suspecting a master cylinder. Are we on the right track? It does have ABS and traction control as well. One thing we are not sure of is if there is no need for ABS or traction control do these systems affect the normal brakes?

Re: 05 Elantra Fading Brake Pedal

Posted: Tue Aug 28, 2012 11:57 am
by jbadenoch
if no abs event is occuring and no abs light is lit then your probably looking at a mechanical issue. If it were a dump valve in abs or something, I would think that pumping the pedal wouldn't make a difference. I would clamp off all 4 brake hoses then try pedal. If pedal feel good then release clamps one by one, while holding pedal pressure, until you feel the pedal drop. When it drops then you have identified which wheel. Frozen slide pins, pad stuck in anchor, hose swelling, air in caliper, caliper itself. If the pedal still feels crappy after clamping hoses then I would say master cylinder or air trapped in system.

Re: 05 Hyundai Elantra - Fading Brake Pedal

Posted: Tue Aug 28, 2012 6:56 pm
by Tim Martin
This vehicle has the arrangement where the parking brake is part of the rear calipers. What is the chances of that malfunctioning - say out of adjustment or something like that? Could that create the symptom we are seeing?

Re: 05 Hyundai Elantra - Fading Brake Pedal

Posted: Wed Aug 29, 2012 2:10 am
by steven kiser
Pressure bleed the system and check to see if caliper slides are free or a pad is misaligned. There may be a prop valve near the rear brakes with a bleeder screw on it. At this location a small amount of air will cause issues as you describe. If you yank up on the e brake does it effect the pedal? If it does the drive screw in the caliper may be broken because some whiz bang worked like a dog to collapse the piston by pressure instead of twisting it in.

Re: 05 Hyundai Elantra - Fading Brake Pedal

Posted: Wed Aug 29, 2012 3:52 am
by jbadenoch
clamping off rear calipers will let you know if any issues

Re: 05 Hyundai Elantra - Fading Brake Pedal

Posted: Thu Aug 30, 2012 2:19 am
by steven kiser
I agree that clamping off rear caliper will help with diagnosing but it can also damage hoses.If i'm going to pinch off a brake hose i will place a quarter on each jaw of the vice grips to broaden the pinch area or use vice grips with a swivel pad on the jaws. I am thinking it's either a frozen caliper slide, bad rear caliper because of a broken internal piston screw or possibly a bad wheel bearing causing the rotor to lean into the caliper.

Re: 05 Hyundai Elantra - Fading Brake Pedal

Posted: Thu Aug 30, 2012 6:26 am
by jbadenoch
Yeah, clamping can cause damage, and i like the quarter idea. I have a set of clamps meant for brake hoses. They have rounded edges and tighten screw by hand, still being careful. Curious to hear what he finds.