longitudinal i4 - how to tell if engine mounts are bad

[JHZR2]

Hi,

I have an I4 BMW - a 318i.

Id like to know how to tell if the engine mounts are going bad. The car idles smooth, it runs smooth, no issues to notice. However, if I rev it from idle, just a blip of the throttle - in neutral, it feels to me like the engine is moving or shifting slightly. I am not under the hood to see, but the car definitely takes a sideways jerk.

I was under the impression that motion or jerkiness when making quick chaqnges in throttle is an indicator that the engine mounts are bad. Is this the case?

Any insight would be most appreciated.

Thanks!

JMH

 

[Gary Allan]

I don't recall how the shifter is fastened in the BMW. I know that when I've had bad motor mounts ...when you hit the gas with the trans connected ..that shifter takes a leap sideways.

 

[olddognewtrks]

If you have access to a hydraulic engine hoist, hook it up and see if the engine shifts/lifts when you try to lift the front of the car via the engine. And ignore all the cheap-guy advice below. Otherwise....

I broke first one motor mount, then the other, on an old V-8 Chevy I had years ago. Here's what I did, on the quick and dirty, because I didn't have access to an engine hoist. The car had a slushbox.

You'll need another person; one observes, one "drives". Make sure your eager helper understands that they watch from alongside the fender, NOT THE FRONT OF THE CAR. And make sure you have lots of light.

Get lots of big wheel chocks. For an automatic (you didn't specify) set the parking brake, and then brake torque it slowly/gently in low while the observer checks for obvious movement. If it's a manual, you'll only sacrifice a smidge of clutch lining. Only this time, do a toe/heel so it won't creep forward. Don't get too vigorous-you're only looking for it to rise and settle back down onto the mount. You don't want to bounce the engine around and break something. If there's still doubt, repeat the procedure in reverse.

If one is broken, you can probably drive it gently to wherever it will be fixed. If somehow you've got two at once, I'd tow it in.

Good Luck, and let us know how it went.

[ August 18, 2006, 12:57 AM: Message edited by: olddognewtrks ]

 

[jmacmaster]

You can also: (1) clean the mounts and then check for cracks and tightness of the fasteners, or (2) I've been told that dealerships and some independent shops have the computer technology to hook the vehicle up to a diagnostic program that will check for motor mount problems (which is a check that I personally would not trust).