Ford - Focus :: 2004 - Grinding Noise From Front Passenger Side

I've had a grinding noise coming from the front passenger side, sounds like the wheel area of the car, for many months. I've driven thousands of miles on it like this, mostly because I'm broke and the car otherwise runs fine, but also because when I've taken it to mechanics, they are stumped.

I took it to a shop about a year ago and he had it for a week, had different specialists look at it and ruled out anything mechanical (wheel bearing, etc.) In the end, he threw up his hands and didn't want to give me any more free labor for his non-diagnosis, and thought he ruled out everything but the transmission. I took it to a transmission shop recently, and the guy ruled out right away that it was the transmission. He tried to diagnose the problem and was stumped too.

Here's what it is doing. It makes a grinding noise around the front passenger wheel when I accelerate. Only when I accelerate. It seems to be more active when it is cold, and after I've been driving the car for about an hour or so, it goes away. It used to only really happen when taking right-hand turns, and that is still when it is at its worst, but now it does it anytime. However--some days it is very bad and some days very light. One day--of course the day I designated to take it to the shop--it stopped altogether and drove like new. Just until I got it home. It is worse in low gears, and used to only happen in first, second and third, but now on an active day I can hear it on the interstate in fifth gear.

The shops I've taken it to can't seem to figure out what it is. Reading threads online, I've learned that people with similar problems found the problem was a bad passenger side motor mount. I have the car at a new shop right now, and I asked them to replace the motor mount, even though it looks fine. I had a long talk with the mechanic there today and he seemed a bit skeptical, but thought it was a possible solution.

Should I spend the money on a motor mount even if it looks okay? (I've also read that the Focus mounts look fine from the exterior when they are bad because they have a gel interior that busts). Especially if this doesn't work, I'm going to be back at square... um, zero.