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?
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.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk Web site.)