I just pulled my bumper last weekend to seal my lights better and to test out some led's. When I was putting it back together one of the headlights wasn't lined up very good and needed adjustment, but I had already put the bumper back and had some of the fasteners on, so I wondered the same thing, could I get to the bottom headlight bolt to loosen it enough without removing the bumper again?
Answer: NO Impossible unless your arm is very skinny and has six elbows. If you could remove your grille from the front with out removing the bumper it might work, but the bottom headlight bolts are long, like 2.5 inches and I don't know how much clearance you would have to back them out.
I even thought about not using those bottom bolts and just letting the headlight hang from the top two but it was flimsy when I tried it, felt like the top tabs wouldn't last long
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Headlight Removal - 
