How can I tell if my motor mounts really need replacing...and is it dangerous if I don't replace them?

Dear Car Talk

Dear Car Talk | Oct 01, 1998

Dear Tom and Ray:

I own a '93 Ford Taurus with 66,000 miles on it. It's been a great car and has
been well taken care of. A service rep at my local Ford dealer told me I have
two broken engine mounts and offered to replace them for about $360. How can I
tell if the mounts are broken and need replacing? How dangerous is it to drive
around with broken engine mounts? -- Jon

TOM: It actually IS kind of dangerous, Jon. The engine mounts have two jobs. One
is to help insulate the rest of the car from the engine's shaking and
vibrations. But more important, they position the engine and hold it in its
proper place in the engine compartment.

RAY: It's not that the engine is literally going to "fall out" of the car when
the engine mounts break, but it may shift around. And that can lead to other
broken stuff, and in the worst scenario, unintended acceleration.

TOM: There have been cases where the engine has shifted in a way that causes the
throttle to jam in the open position. So it is something you want to fix.

RAY: Here's how you can sometimes tell if you need motor mounts. You find
someone you love and trust ... someone who doesn't want to kill you (i.e. not a
long-suffering spouse). You have this person sit in the driver's seat with the
engine running and the parking brake applied. You have him plant his foot on the
brake and, at the same time, put the car in Drive and give it some gas.

TOM: You stand NEXT TO the engine compartment (not in front of the car), and
watch what happens. According to Newton's laws, when the engine's crankshaft
turns in one direction (as you accelerate and transmit power to the wheels), the
engine will want to turn in the opposite direction. And if the mounts are really
broken, you will see the engine twist and lift up, sometimes as much as several

RAY: By the way, you have to do the same thing with the transmission in Reverse
to check the mount(s) on the other side of the engine.

TOM: If you do see the engine lift up, then you need new engine mounts. Of
course, if your friend takes his foot off the brake, you'll need a new front end
and a new garage door, too. So be really careful. Or better yet, find a mechanic
you trust and ask him to do this test for you if you want a second opinion.

* * *
Wait! Before you buy a car, make sure you read Tom and Ray's guide, "How to Buy
a Great Used Car: Things Detroit and Tokyo Don't Want You to Know." Send $3 and
a stamped (55 cents), self-addressed, No. 10 envelope to Used Car, PO Box 6420,
Riverton, NJ 08077-6420.


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