Is it safe to keep driving with two busted CV boots?

Dear Car Talk

Dear Car Talk | May 01, 2001

Dear Tom and Ray:

I drive a 1989 Mazda. When having new tires put on the car last week, the mechanic at the tire shop told me that both of my outer CV boots were split and the grease had leaked out. I took it to another mechanic, who I'd used before, and he tried for hours but couldn't get the axle out of the hub to replace the CV boots. He finally told me that I should just drive the car as is and that the CV boots were not safety-related. How important are CV boots? How much damage will be done to the axle if I don't replace them? And are they a safety concern? I have a 2-year-old child, and I definitely want the car to be safe. -- Robert

RAY: Well, CV (constant velocity) boots are important only because they cover your CV joints. It would be like your winter boots, Robert: If they failed, would that be a safety issue? Well, not immediately, right? But eventually, your feet would get pretty beat up.

TOM: The same is true of your CV boots, which protect the CV joints. Your CV joints are complex, ball-and-socket joints that transmit power from the transmission to the wheels. These joints are covered with rubber boots that get stuffed with grease.

RAY: After a while, these boots can crack or get torn by road debris. Then the grease leaks out and leaves the CV joint exposed. And then it's only a matter of time before the joint fails.

TOM: And is it a safety issue? Well, a broken CV joint is not going to make the wheel fall off or anything exciting like that. But it will interrupt the flow of power to the wheels. And without power, your car won't go anywhere.

RAY: You'll get plenty of warning that the CV joint is failing -- most notably a clacking sound on acceleration, especially while turning. But if the joints happen to fail completely when you're crossing a railroad track, that would certainly be a safety concern, wouldn't it, Robert?

TOM: Plus, the joint is much more expensive than the boot. So -- safety aside -- it absolutely pays to fix the boots when they break.

RAY: Sometimes it IS hard to get the axle out of the hub. But there is a way to do it. I'd take it to another shop and ask the mechanics to remove the axles along with the steering knuckle. Then they can put the steering knuckle in a hydraulic press and press on it with, say, 25 tons. Sometimes we even have to soak the axle with penetrating oil and heat it up, but they all come out eventually.

TOM: The worst that will happen is that a wheel bearing will break. But if that's the case, you just replace the wheel bearings, which is not a big deal.

RAY: But giving up is not a good solution, Robert. Eventually the joints are going to fail, and you'll be in the same predicament you're in now -- except that the parts will cost you more. Good luck.

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