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Motor Mounts: To Replace or Not to Replace?

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motor mounts
Dear Tom and Ray:

I've never given my engine mounts a second thought until my Acura mechanic advised me that my 2001 MDX with 95,000 gently acquired miles was showing "engine mount wear" and that the front and side engine mounts "ought to be replaced." This is my lovingly maintained and leisurely driven luxo-truck, which has never experienced anything akin to an "off-road" experience or even modest abuse. So, are we talking rational preventive maintenance, or is my dealership's mechanic looking for something to do to this otherwise problem-free vehicle? Dropping the front sub-frame and lifting the engine to install the mounts sounds like a serious invasion of my vehicle's personal space, not to mention the $700 lightening of my wallet.

-- Robert

RAY: Your engine mounts may very well be showing signs of wear. But that doesn't mean you have to replace them right now, Robert.

TOM: Engine mounts, sometimes called motor mounts, essentially are rubber blocks that both hold the engine in place and help to isolate the engine's vibrations from the rest of the car. That's so you don't feel like you're driving one of those motel beds that takes quarters.

RAY: In fact, that's often the first sign that a motor mount is failing. You'll feel a lot more vibration when the car is in drive and you're stopped at a light, for instance.

TOM: Over time, rubber degrades from getting dried out and from being attacked by the ozone in the atmosphere. So all older mounts show some signs of wear.

RAY: The real question is whether there is any sign that they are broken or stretching excessively.

TOM: The way your mechanic will test your engine mounts is by putting the car in drive or reverse, planting his foot on the brake and giving the car some gas.

RAY: If a mount is broken, an observer looking in the engine compartment will actually see the engine lift up and twist. With a broken mount, we've seen an engine move as much as a foot.

TOM: If it's stretching more than it should, which suggests it may be getting ready to break, the engine still will move more than it should -- and a trained eye will be able to see that.

RAY: But in your case, since you don't trust the trained eye you're dealing with, get a second opinion, Robert. Check the Mechanics Files on our website (www.cartalk.com), plug in your ZIP code and search for a highly recommended mechanic near you. Then ask him to test your motor mounts.

TOM: If they're not actually stretching or broken, I'd leave 'em alone.

RAY: Even if they're old, cracked and decrepit-looking, like my brother, if you drive gently, they could last a long time before actually breaking. Years, even. 
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