The number one rust issue,...
The number one rust issue, by a long shot, is floor pan perforation. The Mustang’s floors rust from several factors, including leaking cowl vents, tire splash, lack of exterior protection in harsh climates, leaking windshield gaskets, and even leaking convertible tops.
The Mustang’s cowl vents (shown...
The Mustang’s cowl vents (shown here after removing the top of the cowl for repairs) are themselves a rust issue. However, once they have began to rust and allow water into the interior the rust continues due to wet carpets and trapped water, rusting the firewall, toe boards, inner rockers, floor supports, and the floor itself.
A jewel like this early fastback...
A jewel like this early fastback might be considered by some a great project at a low entry price for getting into the hobby, but you’ll spend thousands of dollars in sheetmetal and labor just getting the car back to a solid foundation to build from. If you have the skills and tools to do so that’ll save you some money, but don’t expect any car of this condition to be a cheap build that you’ll have on the road in just a few months (try a few years!).
1: Structural/Sheetmetal Rust
This comes as no surprise to anyone that has ever worked on a vintage Mustang that rust issues are the number one Mustang problem. From damage due to daily driving in the “rust belt” to improper accident repair damage, rust is the arch nemesis of vintage Mustangs. But don't think it is a vintage only problem; not by a long shot. We've seen many a Fox Mustang and even some SN95 Mustangs with rust issues due to winter driving, salt air from the ocean, or bare metal left from repair work. Repairing this rust damage can be a long, drawn out process, as you will often find that as you cut away the rust damage you'll find more rust damage behind/underneath. If your quarter panel has some rot to it you'll rarely get away with just a quarter skin replacement. The typical repair includes the trunk drop-off panel and the outer wheel house (at a minimum).
Besides rust repair being such a large project it is also an expensive one, causing lightened wallets across the hobby. Sheetmetal is not cheap, and often you'll find small brackets/braces that are not reproduced and hard-to-repair areas that you simply have to create custom patches for. The job is a messy one that requires plenty of room for tear down, support of the structure for proper repairs, lots of cutting and grinding, and of course welding the new metal/patches in. It's a dirty job Mike Rowe would be proud of and also takes a fair amount of skill and knowledge to understand how the Mustang's unibody is connected to prevent causing more damage with a poor repair.
We've said this before in various buyer's guides but it pays to state it again—buy the cleanest, rust free Mustang you can. Short of a family heirloom you'll often spend more than the cost of the car just in metal repairs and prepping the body for paint. Frankly, rust repair is the one major project we see most where people give up and abandon their dream project. Know what you're getting into before you buy and for those lucky enough to already have a Mustang in their garage you need to be vigilant about keeping the car clean. Ensure the body and door drains are clear to allow water to escape. Keep the car out of the weather as much as possible with garage storage.
A Word of Thanks!
While we've been in the hobby long enough to see all of these problems ourselves, we spoke to several others to ensure that we were on the right track. By trading emails, phone calls, and horror stories, this article came together with the help of the following industry friends, and for that, we thank them!
John Clor, Ford Performance Group (and Mustang II fanatic!)
Donald Farr, Editor, Mustang Monthly
Scott Halseth, Ford Product Manager, NPD
Merv Rego, Classic Creations of Central Florida
Rick Schmidt, President, NPD
Jim Smart, Mustang journalist and historian
Dave Stribling, Dave Stribling Restorations
Steve Turner, Editor, 5.0 Mustang & Super Fords