What size allan wrench or tool do I need to adjust the truss rod in a Fender MIM P bass? Still cleaning the dirt out, see below, so I can’t really tell what this needs. I’ve stuck a few wrenches in but nothing seems to fit.

Here’s the story. I bought this bass at an auction for $45.00. It looks like it fell out of the back of a truck. Both volume and tone knobs are sheered off at the nuts. Body has an assortment of dings and scratches. Not the kind you’d get from normal wear and tare. The truss rod entry was packed full of dirt. Bridge is rusted and no longer adjusts. E string tuner is missing it’s bushing. Clear coat is pealing off the headstock. Back of the neck is scratched and marred. But nothing that would impede playing. Fretboard and frets look brand new. Like it’s never been played.

The tuners, bridge and all the electronics need to be replaced. The pickups might work. But with the shape everything else is in I don’t want to plug it in to find out. This thing looks like it hit a gravel road and then was stored in a barn. If I can get the slight bow out of the neck it’ll play beautifully.

It's 3/16".

Pickups almost never just quit working. It's possible that the joints where the leads meet the coil are corroded beyond repair (common only with old hofner pickups for some reason) but as long as the coil itself is intact, repairing it is relatively easy, but very delicate work.

Also, plugging a knackered old guitar into an amp won't hurt anything. It will either work or it won't.
Last edited by Invader Jim at Dec 14, 2014,
Thanks Invader Jim! As soon as I get all this dirt out of the way I'll get right to it.

Not sure if these pickups would work or not. Very rusty. There was a 120 watt 2x12 Ampeg amp that sold at the auction as well. Really bad looking. Missing a lot of knobs. The back was almost solid rust. Swear I could have put my fingers threw the power transformer. Really looks like both the amp and bass were stored in an old shed or barn. Honestly think they guy who bought the amp paid $5.00 for scrap wood.
Just like to post an update. Again Thanks Invader Jim. I kept trying to use metric instead of standard wrenches. The 3/16 fit like a glove. Took a bit of work to get all the crammed in dirt out of that little hole. Right now the base is in pieces. Took everything apart. A lot of rust inside and out. Good to I know I'll be able to fix the neck. Now to get quality parts for it. Put it back together and bang away!

Thanks again for the help!