Posted: 10/25/2010 2:15:13 PM EDT
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So my daughter calls me from college and says her 2000 Ford Focus is having issues. #1 brakes ( front making noise when pressing brake pad , Issue #2 the battery light came on and engine is idling rough. She takes it to AutoZone and they check the Alternator and say it is fine. For the brakes they send her to a fairly reputable car repair place. After keeping it for a few hours they say the alternator has a bad diode and that the brake pads and rotors need to be replaced. The brakes just started making noise, so I say it is the wear indicator tab scraping the rotor making the noise, they tell her the brakes are grinding and not drive it much. Question:Grinding = 's what? Second question: Does a bad diode on the alternator ( which has tested OK two times this past week) cause the engine to idle rough ( not all the time, just every so often). I will replace rotors and pads, but I don't want to replace an alternator that ain't causing the rough idling. Any info would be helpful.
Thanks, BravoCharlie |
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Quoted:
Wouldn't the metal tabs on the pads be heard first before any metal to metal sounds? Just wondering. BravoCharlie True. The indicators will make a high pitched squeal and metal to metal will be grinding sound. the only way to tell for yourself is to look at them. |
| If the alternator isn't putting out enough voltage or the voltage fluctuates, the computer will act crazy. Throw a volt meter on the battery and check the voltage with the engine running about 1500-2000 rpms. You should have at least 13.5 volts. Check the cables and engine grounds also. Floating grounds make electronics do weird things. |
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If they said grinding, it usually means the pads are worn well past the wear indicators, thru to the rivets holding the brake matieral to the backign steel. And the rivet heads are plowing troughs in the rotors. Slight surface damage could be rectified a time or two with very judicious cutting as part of a normal brake job rotor resurfacing. They could either be suggesting new rotors as a money-making opportunity, or they could very well be truly damaged beyond recovery, necessitating replacement.
The screeching of the wear indicator may have been disregarded or thought to be just caused by brake dust. The grinding is pretty hard to ignore. You need photographs of the rotos to judge. The can be taken readily by turning the wheels hard left or right and photographing from under the front corner of the bumper, aiming at the inside front of the exposed rotor. IF the damage has proceeded to the grinding stage, it will frequently be visible on both sides of the rotor. Another remote diagnosis trick is have her describe the noise, without leading her. A silly as it might seem, have her try to imitate the sound. If it's a grumble or heavy vibration / shudder when the brakes are applied, the brakes are destroyed and will shortly be non-operational, given that it was almost certainly her driving / braking habits that pt such abusive wear on them in the first place. It can happen when a brake caliper sticks for some reason, but typically one wheel, one side of that wheel only. If it's both rotors, both sides, it's her driving habits. I don't mean to be offensive or mysogynistic in that remark. It's just truism. The number of women I've encountered with their brakes destroyed in this manner far outweighs the males. Don't know if it's upbringing, lack of mechnical knowledge, what. But by the time many announce a problem it's already progressed far beyond the readily or affordably repaired. |
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Brakes will be no problem to replace, rotor & pads. It's the $200.00 for an alternator( and that's me installing it) that I am not sure is the problem. How does a alternator that is keeping the battery charged, reported by one repair shop to have a bad diode , cause the engine to idle so low that it sounds like it may die and it doesn't do it all of the time. Also, the battery light is on and the battery is good.
BravoCharlie |
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Quoted:
She should go and have the codes read. If it's idling very low, the problem might not be the alternator. It might be the idle air control. The codes will help point you in the right direction. To add: the low idle could be so low that the alternator isn't charging. IAC passages are a known issues on late model Fords. FWIW, an alternator can test good at no or low load and bad when you put a heavy load on it. |
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Well. daughter drives home today ( 80 mile trip ) no battery light and no rough idle. I change brakes and rotor. Take car to AutoZone, they run codes and nothing shows bad, they check alternator under load and show nothing wrong with alternator, they check the battery and it's OK. She goes to get gas for return trip and check battery light comes on. She starts the car to leave, light out. She gets 50 miles down the road, light comes on. No rough idling at anytime. ????????????????????????????????????????????????? I give up!
BravoCharlie |