tell your friend to save his money and buy a REAL car? save yourself time later down the track trying to sell your car for a ridiculous value people wouldnt think twice about paying? i.e mid-high...
sounds like rear gearbox mount or mounts ! check all your mounts for wear and tear.
usually rear engine mounts are the culprit for knocking off and on throttle.
what are you basing your assumptions on ?
i.e. the fan is not working because its overheated and the fan still hasnt turned on ? or the fan is not working because it doesnt turn on after i let it...
best way is to check part no's. matching ones usually mean same piping, size etc...
and your probably posting int he wrong thread. has nothing to do with all motor.
as above mentioned ^ Jack up fronts , rad cap off, heater on full blast to encourage flow, let car idle until ur fan turns on about twice. sitting it flat will definitely not release all the air...
i've never heard of reconditioning engine mounts nor do i think its worth it, they dont even cost that much 2nd hand, and sometimes they give you warranty on them(wreckers).
FYI you dont replace...
depends on your preference my man. check out the shore hardness on their website. standard rubber mounts are around 40 you should probably go harder like 50-60.