Alternator won't pipe down when engine is revved up

  • Article by: PAUL BRAND
  • Updated: June 8, 2012 - 3:46 PM

Engine-related whistling noise is still there after alternator is rebuilt.

Q I have a 2008 Jeep Liberty with 71,000 miles. Last fall, at about 60,000 miles, it began to make an engine-related whistling noise. It usually appears after the engine is warmed up, and only above 2,000 rpm. Revving the engine brings the noise, which pulsates rapidly according to rpm. It seems to be coming from the alternator. The dealer replaced the EGR valve and the serpentine belt with no improvement.

A mechanic confirmed the alternator as the source of the noise. An automotive electrical shop completely rebuilt the alternator with new bearings and installed a new serpentine belt tensioner. But the noise is still there after all of this work. The shop finally concluded that the alternator was squealing when working under load and that it must be normal. Is this correct?

AWhy not have the shop or dealer measure the amperage output of the alternator under normal operation? Assuming your vehicle is not diesel-powered, there were two different Denso alternators available: 136-amp and 160-amp. According to my Alldata database, here's how it works: "The PCM or ECM receives a voltage input from the generator (alternator) and also a battery voltage input from the TIPM (Totally Integrated Power Module), it then compares the voltages to the desired voltage programmed in the EVR (Electronic Voltage Regulator) software, and, if there is a difference, it sends a signal to the generator EVR circuit to increase or decrease output."

It would appear that the voltage difference between the alternator, battery and TIPM is great enough to command the alternator to produce higher output. It's worth trying two things: a scan tool to determine specific voltages and any charging system fault codes, and a careful inspection and testing of connections and grounds in the battery/charging circuits.

Does the alternator use a decoupler pulley? This is a one-way clutch designed to "reduce belt tension fluctuation, vibration, reduce fatigue loads, improve belt life, reduce hubloads on components, and reduce noise." Could this be the culprit?

QI have a '97 F-150 4WD with 40,000 miles on it. I was told it needs new ball joints. The joints are not loose, but they squeak. I modified a grease gun coupling with a needle used for pumping up basketballs. By puncturing the boots with the needle, I can pump grease into the boots. Is this a fix, or will the grease fail to migrate into the joint where it will do some good?

AWhile I really like your way of thinking -- can I fix it myself? -- I'm not sure this will do much good. But heck, what have you got to lose? If it doesn't, replace the joints. Also, you may not have to actually puncture the boots. You may be able to pry up the edge of the rubber and slip the needle underneath. By the way, the allowable radial play in upper/lower ball joints is 1/32 inch. And as you've discovered, they are not individually serviceable -- the entire upper or lower control arm must be replaced.

QI have owned a 2006 Chrysler Crossfire convertible for the past three years. Shortly after I purchased the car, I noticed a distinct musty odor inside. If I did not know better, I would swear that the car sat outside during a torrential rain and the carpet got wet and is now molding. However, everything in the car made of cloth still looks great. I have been spraying with Lysol deodorizer to mask the odor for three years and the odor keeps coming back.

AHow do you "know better"? After all, you bought the vehicle used. Have you pulled up the carpeting to check the padding? If it's wet, you've found your culprit. Water can enter through the heater/evaporator box, the windshield, the top or the windows. Try spraying your deodorizer down the fresh air vents with the heater or A/C on and make sure the heater/evaporator drain tube is open.

Car show season is here

The car show season is revving up for the summer. Here are several events this weekend leading up to the big one: "Back to the '50s" on June 22-24 at the State Fairgrounds.

Saturday, June 9

•Boy Scout Troop 042 fourth annual car show, 8 a.m. to 2 p.m., St. Richard's Church, 7540 Penn Av. S., Richfield.

•Roger's Rod & Custom car show/open house, 10 a.m. to 2 p.m., 18689 NE. Buchanan St., East Bethel (behind the East Bethel Theatres).

Sunday, June 10

•30th annual All GM Car/Truck Show & Swap Meet, 9 a.m. to 3 p.m., State Fairgrounds.

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