How can I tell motor mounts are broken - 1996 Ford Crown Victoria

With the park brake on, start the engine with the hood open so you can see it through the windshield. Put it in reverse and give it some gas, if the engine moves up, you have a broken mount. Do the same in drive. If the motor moves up then the mount on the side of the engine that moved up is broken. If these tests don't show a broken mount then your grinding noise is coming from elsewhere.

You need to open the hood. You can have someone stand by the fender and look at the engine while you do this test. Now start the engine and put it into drive gear, apply the brake and step on the accelerator pedal to bring the RPM up a little. The helper must watch how much the engine as it lifts or twists. More than an inch or two you have a broken mount. Now do the same thing in reverse gear to check the other side. This vehicle is a rear wheel drive and will have 3 motor mounts. Left , right (both under the exhaust manifolds) and a rear mount at the rear of the transmission. This mount should be visually checked as well. I hope this helps.

basically pull the motor off the mount
if it is broken then the mount will part
inspection will reveal a shiny part of metal where the rubber is rubbing on the steel

If the mount is bad the engine will lift up when you hold the brake and add a little throttle, it will really jump up of the mount is broken, some movement of course is normal.

Vibration at idle brings to mind a few suspects:

transmission mount(s) broken/missing
transmission internally worn
motor mount(s) broken/missing

(1) transmission internally worn or transmission mount broken/missing - test this by shifting into neutral at the next stop light. If the vibration disappears when you disengage the transmission, then the transmission is the source of the vibration. You'll have to inspect the transmission mounts - if they're ok, then the transmission is internally worn and can no longer smoothly "slip" while idling in drive.
(2) motor mount broken/missing - also test this by shifting into neutral at the next stop light. If the vibration persists, then the transmission is exonerated, and the vibration is coming from (under) the engine. The rubber part of motor mounts commonly crack/break and or pop out and are lost.

A photo of the front motor mount for the 2003 Dodge Neon:

have someone power brake the car, wile you watch for the engine to rise up on its mounts make sure to power brake it in forward and reverse if the mounts are broken there will be a very noticeable lift in the engine. also check the top thrust mounts they look like a dog bone and mount right behind the radiator make sure the rubber bushings are in good shape and their is no movement back and fourth with the engine......HAVE FUN

this is hard to say without seeing it, but the mount is one piece but then you have the bracket part this bracket bolts to the motor and the mount sits in it, and a bolt or nut holds the mount to bracket then the other side of mount goes to the frame.

You can drive the car up to a certain point. If the motor mounts are just worn and not broken you can drive it, but It would be best if they were fixed. If they come loose you have the potential to wreck a lot of stuff, if they are broken, which is usually how you tell if they're bad or not, then I would definitely fix them before driving it.

to check for a bad motor mount u need 2 people for this. Have the car running put it into gear with your foot pressed firmly on the brake u don't want to run your buddy over. Give it some gas in the motor is jumping around alot like 6 inches in any direction you have a broken motor mount. Which way the engine jumps will let u know which one is bad. Try this test in reverse gear to.

You need to loosen the motor mount slightly--just a full turn or two. Place a jack under the oil pan and lift the engine until the strain is relieved on the motor mount and finish removal. Replacement installation is the opposite except you'll want to tighten the new motor mount into place fully (if possible) before lowering the jack.