Ok i have a 1989 f250 4x4. I've had this truck for about 3 years now and the truck hasn't ran for 2 of the 3 years. Now i've got some extra money to replace the motor, brakes, ect. but i'm alittle worried about the frame. Around the engine cross member and the in the rear wheel wells the frame has a lot of surface rust and seems to flaking off. It doens't appear to be rusted through anywhere but i'm wondering if there is a any way to tell if its to thin, how can i check it, or if i shouldn't worry about it.

Thanks

Lr

 

Of all the rust you could have, surface rust is the easiest to rectify, especially on an F250 or F350 where the frame is rather thick/stout to begin with. I just went through this myself, actually, on my F350 crewcab.

Essentially I took the bed off, dropped the tanks, removed fuel lines and such, did a reasonably quick driveway sandblasting job to remove all the loose rust. There was a couple of spots that wouldn't sandblast off, so I picked at them with a screwdriver, then continued to sandblast. I left surface rust that wasn't flaky, and rather tight, as per the instructions on the sealant/primer that I utilized - a product called "Ospho". What ospho does is convert iron oxide (rust) to iron phosphate, chemically, which once dry you can paint over directly, as iron phosphate is considered a primer. OR you can do what I did and just slather on three coats of ospho to seal it up. I didn't bother painting the frame since I never see it

POR15 is another good product to use for this... it's thicker but because it's thicker, you can't "dribble" it between rivited crossmembers and frame rails - POR15 will seal the edges, which is fine until your frame flexes, which they all do. This is why I like the "Ospho" product. It's cheap too, $10 a quart. $20 was all I needed to coat the frame end to end, the outside of both gas tanks, the bumper supports in the back, and the bottom of the bed, and I still have some left over. Goes on with a paintbrush.

If you have holes, that requires a different type of repair usually involved welding patches over things once the frame is cleaned down to the bare metal (with a real sandblaster), or replacement of sections depending if they are still available.

According to my local Ford dealer, the frame and crossmembers of the 87-96 pickups are no longer available - these parts were discontinued last year.

 

thanks for the advice on how to stop/slow down the rust but any ideas on how to tell if the frame is to thin.