yo,
Besides the usual visual, driveability and leak checks, look for:
- oil pan rust -
radiator plastic side seam leaks esp. during engine cool-down period/overnight
auto tranny and transfer case operation - electric push button motor/connector is a prob. area
auto hub operation (get it in sand or mud and try the 4x4 system)
rust in inner rear fender lips and bottom of tailgate (our's was rusting due to beach sand wearing the paint)
radius arm bushing deterioration
cracked exhaust manifold/y etc.

 

I've done that EVERY single time I've washed under there, like I said the inner wheel wells are fine, not even surface rust appears. I'm talking about between those inner wheel wells and the outside fender.


I do think that under coating would help in this situation, BUT I have heard of people clogging up drainage holes and causing water and other crud to stick and cause rust, which would be worse, in my opinion that never washing it because it is trapped.

 

Just don't block the drains. It's easy to cut out undercoating after it dries.

 

Steve, would it be worth while to do on older vehicles? Like in my case, I've got very minor rust, would under coating help to stop more rust from happening?

Would drilling more holes on that side of the fender well help for salt and corrosion to drain quicker.

 

Check out this paint from hirschauto.com called Miracle paint. Use that with their rust prep spray and you'll be good for years.

 

Mustang, have you used any of this yet? we used some POR-15 on one at work, it stopped the bleeding rust, but didn't help at all with rust through, .

 

my 91 250 has NO rust an im in a VERY wintery climit

 

It would slow it down, but rust comes from Oxygen; not water. Water just helps hold Oxygen against the metal, and it also dissolves the rust, forming a mild acid. The undercoating isn't 100% waterproof or anywhere close to Oxygen-proof, so it won't STOP the rust.

It's still a good thing to do - the insides of my doors & tailgate are heavily coated.