With any luck, I'll be picking up a truck this Friday. I've only seen pictures of it and it does have a small spot of thinning/peeling paint a few inches above the drip rail in the center of the truck. The owner tells me there is a very small spot of surface rust there. What should I look for to tell if this really is just surface rust from the thinning paint or the dreaded 'inside out' rust?

If it turns out to be the worst kind, would you turn down an otherwise very nice/clean low mileage truck that I can get for $7000? Its a '93 W250 regular cab auto. Exactly what I've been looking for for quite a while and it's even a good color combo with gray interior - bonus!

 

Surface rust will be just that, the inside out rust should start to bubble down by the drip rail.

 

You can remove the sun visor from the inside roof then look inside the mounting hole. A flexible borescope would be nice for this inspection if you have access
to one.

 

The truck doesn't have a visor, is that usually the culprit for the rust? When I searched the forum last night to learn about roof rust, visors were mentioned several times.

EDIT:
Uhhhhh...Never mind...it's early for me, brain's not working yet...SUN visor on inside of cab yeah, it probably has a couple of those

 

One way to know for certain is to remove the windshield. When I had the cab roof and hood on my truck repainted last year, my body shop man nearly had a heart attack when he discovered rust top center on my cab after removing the windshield, hidden by the rubber seal. From what I have read, condensation develops between the two sheet metal layers in the cab roof causing the rust to develop. Go figure, the underside of my cab is almost clean enough to eat off of, but my cab is rusting out at the very location furthest from road debri. Every once in awhile I shoot some WD40 in there as insurance.

John