CAR TALK

Northwest Arkansas Democrat-Gazette - - STYLE - RAY MAGLIOZZI Ray Magliozzi dis­penses ad­vice about cars in Car Talk ev­ery Satur­day. Email him by vis­it­ing cartalk.com

DEAR CAR TALK: Our 2007 Mazda CX-7 re­cently had its steer­ing pump lock up and burn out the belt. The belt and pump were re­placed, but a week later, the car is start­ing strangely. When we turn the key, there is a loud and fast click­ing sound from the driver’s side un­der the hood, and the en­gine doesn’t even at­tempt to turn over. Af­ter a few tries (about 25 sec­onds’ worth some­times), the starter will en­gage, turn over the en­gine, and the car starts right up. How­ever, while we drive, var­i­ous warn­ing lights flicker on and off, like the trac­tion-con­trol sys­tem and air-bag lights. What is hap­pen­ing that causes the click­ing sound? Is it the starter so­le­noid fail­ing to ac­tu­ate the starter mo­tor? Or is it some­thing in the elec­tri­cal sys­tem, and my me­chanic didn’t do a thor­ough enough check?

— Ben­jamin DEAR BEN­JAMIN: When you hear a rapid click­ing noise, it’s usu­ally be­cause the starter mo­tor isn’t get­ting enough cur­rent from the bat­tery. You’re hear­ing the starter mo­tor’s so­le­noid try­ing to en­gage but fail­ing to.

So, it could be a fail­ing bat­tery; it could be a bad al­ter­na­tor that isn’t prop­erly recharg­ing the bat­tery; or it could be some­thing as sim­ple as a bad con­nec­tion at the bat­tery. You need to take it back to these guys and have them do a com­plete test of your charg­ing sys­tem. That would in­clude test­ing the al­ter­na­tor out­put and load-test­ing the bat­tery.

Could it be re­lated to steer­ing pump fail­ure? It’s pos­si­ble. If the belt got re­ally chewed up, some de­bris could have got­ten into the al­ter­na­tor and caused it to fail. But it also could be co­in­ci­dence. If the bat­tery is on the edge of fail­ing, that could just be due to old age.

Or the whole thing could be ex­plained by your me­chanic’s fail­ure to tighten the bat­tery ter­mi­nal. If he re­moved the neg­a­tive ter­mi­nal from the bat­tery to dis­con­nect the power be­fore do­ing the re­pair, and then for­got to retighten it, that would ex­plain ev­ery­thing.

A loose con­nec­tion would ex­plain why the starter can’t get enough juice some­times, but then even­tu­ally starts right up. It would ex­plain why lights on your dash­board are com­ing on and off — as you drive around, the ter­mi­nal clamp jos­tles around as you go over bumps.

And best of all, it would cost noth­ing to fix. Un­less you count the price of em­bar­rass­ment that your me­chanic will ex­pe­ri­ence. So ask him to check that first, Ben­jamin.

DEAR CAR TALK: My 2017 Toy­ota Ta­coma calls for 33 pounds of air in all four tires. Where I live, dur­ing cer­tain times of the year, tem­per­a­tures can range from a high in the 70s to a low in the 20s and back to a high in the 50s, all within two or three days. This makes tire pres­sure dif­fi­cult to main­tain. What are the safe high and low lim­its for tire pres­sure? I know if I go with 35 psi, I will have a hard ride and bet­ter gas mileage. If I go with 29 psi, I will have a softer ride and worse gas mileage. But for safety, when do I need to ac­tu­ally ad­just it, in ei­ther di­rec­tion?

— Gary DEAR GARY: It’s al­ways bet­ter to go too high than too low with tire pres­sure (to a point).

As you say, tire pres­sure changes along with the out­side tem­per­a­ture. For ev­ery change of 10 de­grees in the out­side tem­per­a­ture, tire pres­sure changes about 1 psi. So if you fill your tires to 33 psi when it’s 75 de­grees out, and it drops to 25 de­grees at night, your tires will be at 28 psi. That’s too low.

I’ve been told that most tire- pres­sure mon­i­tor­ing sys­tems warn you when your tire pres­sure drops by about 10 per­cent. For you, 10 per­cent would be a lit­tle less than 30 psi.

Low tire pres­sure al­ways is more dan­ger­ous than high tire pres­sure. When tires are de­flated, more rub­ber touches the ground, the tires heat up and you’re in dan­ger of a blowout. If you re­mem­ber the Firestone/Ford Ex­plorer fi­asco, the ag­gra­vat­ing fac­tors that led to many of those flawed tires ex­plod­ing were heat ( high road tem­per­a­tures) and low tire pres­sure.

Higher pres­sure gen­er­ally is not dan­ger­ous, as long as you stay well be­low the “max­i­mum in­fla­tion pres­sure.” That num­ber is listed on each side­wall, and is much higher than your “rec­om­mended tire pres­sure” of 33 psi, Gary.

So, in your case, I’d rec­om­mend that you put 35 or 36 psi in the tires and just leave it there. You won’t no­tice any dif­fer­ence in tire wear, han­dling or brak­ing.

And even if the tem­per­a­ture drops 50 de­grees, you’ll still have 30 psi or more, which should keep your “low pres­sure” warn­ing light turned off.

And if the tem­per­a­ture goes in the other di­rec­tion, no harm will be done. As you say, at worst you’ll end up with bet­ter fuel econ­omy and a slightly firmer der­riere mas­sage while you drive around, Gary.

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