Today: Should you dress your car's belts?

Dear Car Talk

Dear Car Talk | Jun 01, 2010

Dear Tom and Ray: Belt dressings? Yes or no? I heard on your radio show this week not to spray belt dressings on serpentine belts. I recently was told TO use belt dressings on my serpentine belt by a mechanic. He said it would increase the longevity of the belt -- replacing the lost oils and keeping it more flexible and, therefore, increasing the life of the belt. Why is this not good on today's belts?

-- Bruce

TOM: Well, I've found that dressings tend to expand MY belts. Especially Newman's Own. That's why I've switched to the Light Italian.

RAY: The problem with belt dressings is that they're temporary solutions. They just cover up a problem, rather than solve it.

TOM: Most belt dressings contain either a lubricant of some kind, to allow the belt to slip more, or a tacking agent, to allow the belt to grip more.

RAY: The problem is that these agents -- and the solvents that are used as spray-can propellants -- can cause modern belts to swell and delaminate. Belts are made of several layers of rubber, and when they delaminate, these layers come apart and the belt fails.

TOM: In most cases, when a belt is making noise, it's because it needs to be tightened or needs to be replaced. Belt noise also can be caused by a bad belt tensioner or a misaligned pulley. But belt dressing isn't going to address any of those problems in the long term.

RAY: Of course, if you know for a fact that your belt is just old and worn out -- and it's not a tension, tensioner or pulley problem -- and the noise is driving you nuts, and you just want to keep the belt quiet for a couple of weeks until your in-laws leave town, then spray all the dressing you want on it.

TOM: But I don't know of any maker of serpentine belts that approves of belt dressing for its products. And it's a short-term band-aid at best. So dress your salads, and tighten or replace squealing belts, Bruce.

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