pls dont judge mistakes happen. i was going down the mountain on a very rainy day and a large branch hit the bottom of my fiat and i wasn't able to avoid it on time. After this incident my car has been making a knocking noise as if the engine is loose. how much do you guys think this repair will cost? coming from a broke college student. i know there are four parts to the mount, and was told that maybe its $300 per mount part. is that a good price, pls dont let me get scammed like my last mechanic did me like.
I doubt that the engine is loose. In fact, I doubt that the engine was even struck by the branch, so it may be a relatively simple issue.
Under the car's front bumper/fender there will probably be a polypropylene plastic undertray, which is designed to keep dirt/water/debris out of the engine bay. The undertray is fairly flexible (it wouldn't last very long if it was brittle...) but it could be that the branch has still managed to crack it, or more likely shear off some of the mounting screws.
If the screws have been ripped out, the tray will bang against the bumper and/or the engine and/or the suspension subframe etc. so you'll hear a knocking. Get on your hands and knees in front of the car and have a peer underneath. You'll be able to see whether you have an undertray and/or what's loose down there.
If you don't have an undertray fitted (they tend to fall off, as above, or not get re-fitted when the mechanics service the car) .. or even if you do, then the branch may have damaged the exhaust mounts. The exhaust is bolted to the engine but then is suspended on rubber donuts. You may have pulled one of the exhaust hooks out of its donut, or the donut might have been ripped off the car.
In this case, the exhaust can flop about and strike the car body underside, so get a new donut, or replace the hook into its donut if it's still there, otherwise the exhaust might fracture, without proper support. Get a burly neighbour to crawl under there and have a look.
I really doubt the impact forced the motor out of position so much that the mounts got damaged. Normally debris stikes the sump, which being alloy tends to crack.. so unlikely that this is something that serious.
Ralf S.