Is there a easy way to tell which parts are repairable?

[MagpieOAO]

Seems Red is junk, Orange can be repaired, but some things you can't and some you can it seems. Trying to recall but things like push rods I couldn't repair while I could repair drum brake pads somehow.

[Smoke79]

Going to the repair bench is the easiest way after you remove a part from a vehicle, if you see it listed you can repair it, basically belts, bushings, rollers, pulleys, cam gears. fuel filter, CPU's, fuses, wires, coils, spark plugs, windows, seats, steering wheels,[headlights,taillights (some)] are not repairable

[rog55]

try this guide its 95% complete just last few dlcs not added
https://steamcommunity.com/sharedfiles/filedetails/?id=2599847138

[astrofelix59]

As above, if it's electrical, springy or has a lot of movement, probably can't be fixed.
Anything below 15% not repairable, except batteries, they can be charged from 1%, EV batteries can be repaired (+15%) but don't need charging.
No real rhyme nor reason for the exceptions to the rules, but there's not that many.
Head and tail lights, mods yes, Vanilla no.
Pistons, rings and rockers also no. Shock absorbers/parts no, except air shocks they can be.
Most camshafts can be, except a couple of the V8's like CGM, OHV C (1 or 2 others). Likewise most fuel rails can except a couple of V12's.
Being able to repair drum pads, was likely just to "balance" the fact the lathe wouldn't do the drums. (cheaper than adding new animation)
Another fun exception is the right rear window on the Pagani, only bit of glass to be repaired, chalk than one to a crunch time dev not checking that box, probably. (may have been fixed by now)

Good things to collect from junkyard (if you're into that kind of thing) are; oil pans, driveshafts, ABS P/M, engine heads/blocks, brake servo, wheel hubs/knuckles, swing arms, crossmembers and axles. The parts most often missing from junkyard cars. Most of the value of expensive cars is in the panels so big savings can be made there.
Gearbox, blocks and other high ticket items are best for repair and sell, little profit in parts worth less than 1k new in shop. Best value for the cheaper parts to be used in a build.

[Hans Blitz]

Inspect them, they show a colour, red needs replacing.