Just curious, this means hit the gas while holding the gas pedal down? And/or parking brakes on? If so, does that burn a bit of the brakes and/or tires in doing so?
Should I assume at the shop they don’t use the brakes, and just have the car on rollers so it goes nowhere while revving up in drive or reverse? Or that’s not quite how they do it?
Yes brake with your left foot and put the gas up to 1/4 of the way down to test. If they had it on rollers there wouldn’t be torque ond the engine and the test wouldn’t work.
Forget it! Youve demonstrated that you don’t know enough about how cars work to do anything more than drive to a mechanic and say “please check ny engine mounts”.
Really?? That is cute…
I have broken multitudes of RWD motor mounts, I have never had to replace one of my personal FWD mounts… I’ve replaced a lot of customers though… lol
And full size V8 GM vehicles break a lot of mounts also… It depends on the design etc…
I guess you have never revved the engine in an old Mopar with a 440ci engine, the vehicle looks like it is trying to roll over on it’s side… 
Seems like RWD mounts last a long time or suddenly break whereas FWD mounds go bad but don’t break apart.
That’s incorrect. The torque load comes through the driveshaft.
Yup, break a motor mount on a RWD with mechanical throttle linkage, throttle goes wide open. Once on a Pontiac, once on a Studebaker 289. Broke a mount on V6 T-Bird, but that may have had a cable operated throttle.
Tester
The mounts act like a spring. Testing is done the same way as testing any other spring, apply a known force, and measure the deflection. For example valve springs are tested (out of the engine) by applying a specified force, and measuring their deflection (mm shortening ). All springs (approximately) obey Hooke’s law: Deflection = k * Force, or k = Deflection/Force. K is the number that tells you if the spring is working as designed.
Engine/transmission mounts act as any other spring. The only difference is they oppose the force in the rotational direction. So the way to test them is to apply a known force, measure the amount of rotation, and calculate their spring constant k, then compare the measured k to what it should be per the manufacturer’s specification. Figuring out how to apply a known force is the main problem. You can’t get an accurate measureent of k without knowing the exact torque (rotational force) being applied. this is why I prefer the engine rpm acceleration method. It uses the rotational inertia force. Not easy to measure but very easy to repeat. So if you note the amount of rotational movement when the mount is known to be good, all you have to do for later tests is compare to that. A mechanic could apply whatever force they want using the D & R, step on the brake and gas pedal, method, so could conceivably make a mount appear bad when it is actually good. Another problem, how is this done accurately if the car is equipped with a manual transmission?