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

DEAR CAR TALK: I have a 2004 Sil­ver­ado 4WD Z71 that I bought new, and over the years, the brakes have got­ten ter­ri­ble. I’ve been through the typ­i­cal brake fail­ures from rusted lines over the past six years and sur­vived them all. So far.

I love the truck. It still drives and han­dles well. The prob­lem is that the brakes have no brak­ing power. I have re­placed all four ro­tors, the rear calipers, the brake booster, as well as the mas­ter cylin­der, and, of course, all pads have been re­placed at dif­fer­ent times as they wore out. This truck will not lock up the brakes from any speed (barely on gravel).

The only thing that has not been re­placed are the front calipers. Could they have lost power over the years, even though they never stick?

I wouldn’t mind spend­ing $400 to $500 more to get “like-new brakes,” but I hate to spend it if there’s no guar­an­tee of suc­cess. Any ideas?

— Greg DEAR GREG: Well, one more un­timely brake fail­ure, and you could be look­ing at a 2017 Sil­ver­ado. That’s one idea.

Ac­tu­ally, disc brakes aren’t sup­posed to lock up. But we’re go­ing to ac­cept that the brakes are not as good as they used to be. So my first idea is to make sure there’s no air in the brake sys­tem.

You say you re­placed the rear calipers. A lot of peo­ple don’t know that after re­plac­ing the rear calipers, the brakes on all four wheels need to be bled. If there’s some air trapped in the sys­tem, that would cer­tainly di­min­ish your brak­ing power. So bleed all four calipers, if you re­ally know what you’re do­ing. Or pay some­one to do it for you if you’re not sure.

We use some­thing called a power bleeder at the shop, which pres­sur­izes the mas­ter cylin­der. That makes the job pretty much fool­proof, as long as you can count to four — which five out of seven of our guys can do.

While you’re bleed­ing the calipers, my sec­ond idea is to take a look at the wear on the pads, par­tic­u­larly at the front. If the front caliper slides are not work­ing cor­rectly, you’ll of­ten see more wear on the in­ner pad than on the outer pad. Those slides are sup­posed to pull the two pads to­gether around each ro­tor. But if only one pad is do­ing all the work, the truck will take longer to stop. And since the front wheels do most of the stop­ping, bad caliper slides could make a big dif­fer­ence.

But I wouldn’t go spend­ing hun­dreds of dol­lars to change the front calipers without ev­i­dence that they’re faulty. Check the pad wear first, and see if the ev­i­dence is there.

Fi­nally, even though you re­placed the power brake booster, it’s pos­si­ble that the booster isn’t get­ting enough vac­uum. There’s a hose that runs from the en­gine man­i­fold to the booster that could be col­lapsed or some­thing.

You can go to the auto parts store, take that hose off in the park­ing lot, ask them to sell you a re­place­ment, and then put the new one back be­fore you drive home. It’s cheap and easy. And you’ll know right away if it makes any dif­fer­ence.

In the mean­time, wear sneak­ers so you can open the door and drag your foot if nec­es­sary. Good luck, Greg.

DEAR CAR TALK: We have a 2010 Volk­swa­gen Jetta. The air con­di­tioner takes at least 15 min­utes to get to a low tem­per­a­ture. Un­til then it blows plain old hot air.

Once it does get cool, it will stay cool for a good length of time. But then it will get less cool for a while and then go back to cool again. Also, it seems that it starts to cool once the en­gine tem­per­a­ture reaches 190 de­grees.

We have been to the VW dealer, and they have not been able to fix the prob­lem. They have now said, at this point, we need a whole new air con­di­tion­ing unit. We hate to spend $1,500 for a new unit when there could be an­other so­lu­tion to this prob­lem.

My hus­band and I are so con­fused. Is there an­other so­lu­tion?

— Cyn­thia DEAR CYN­THIA: There’s al­ways an­other so­lu­tion, Cyn­thia. There’s rolling down the win­dows, or putting a five pound bag of ice on your lap.

It sounds like you may very well need a com­pres­sor. That is in­deed the $1,500 so­lu­tion. I as­sume they’ve ver­i­fied that the re­frig­er­ant level is fine, or even recharged it for you.

But there’s a small chance you just need some­thing called a high pres­sure switch. If the pres­sure of the re­frig­er­ant in­side the com­pres­sor is too high, the high pres­sure switch will cut power to the com­pres­sor clutch, so the com­pres­sor doesn’t blow it­self up. And while the com­pres­sor clutch is de­ac­ti­vated, you’ll get hot air. So maybe that switch has gone hay­wire?

Nor­mally, a scan will pick that up. But if the switch wasn’t mis­be­hav­ing when your dealer had the car, he could have missed it. And the dealer may not have wanted to put in the time to in­ves­ti­gate fur­ther. He’s too busy try­ing to fig­ure out where to park all those VW diesels he has to buy back.

So I sug­gest you take the car to an air con­di­tion­ing spe­cialty shop. Let them di­ag­nose it, and ask them to check the high pres­sure switch, too. The switch is cheap. But even if they con­firm that you need a com­pres­sor, get an es­ti­mate from them. Who knows? Their price might be cheaper than the dealer’s.

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