Rust Free???

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mbrew2

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Oct 30, 2016
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My Car
1973 mustang convertible
This may be one of those "Don't look a gift horse in the mouth" questions but I have to ask. How plausible is it to have a 1973 convertible that spent 35 years in the eastern Maryland/Washington, DC area and then another 10 years in coastal Florida/Gulf of Mexico area to be "rust free"?

When I bought this car in 2016, I went over it thoroughly with a paint thickness gauge and could find no evidence of body filler anywhere except for a probable accident repair about midway up the driver side door. While having repairs made (transmission and front suspension) the mechanics volunteered as to how clean and solid the car was underneath. Being a little surprised and having expected the worst, while it was on a lift having the front suspension replaced I asked to borrow a hammer from the shop owner. I then, with a bad attitude, proceeded to beat the crap out of every piece of metal that was exposed - trunk drop-offs, frame rails, rockers,  floorpan and as much of firewall as I could reach. My intention was that if there were any soft areas, I was going to go ahead and knock a hole in it so that I would know what repairs were needed. Other than some light surface rust - nothing - solid as a rock. I did find a small rusty area at the bottom of the driver front fender near the door/cowl area but nothing that needed immediate attention. That was 3 years ago.

 I recently discovered 3 small pin-holes in the driver rear quarter behind the wheel. Can't see these from the outside because they are in the black accent paint just below the accent moulding but can see light coming through when looking into the trunk drop-of. Front fender rust spot has gotten worse and will soon need repair. 

When i bought the car it came with a notebook full of detailed mechanical repair records covering 20 years but there was nothing mentioning bodywork. I know that the car had been in a minor wreck and had been repainted sometime after 2008 but none of that is in the records.

I guess my question is : If its not reasonable for the car to survive this long with no metal repair, how do I tell if floorpans, trunk, body panels have been replaced ?

 
This may be one of those "Don't look a gift horse in the mouth" questions but I have to ask. How plausible is it to have a 1973 convertible that spent 35 years in the eastern Maryland/Washington, DC area and then another 10 years in coastal Florida/Gulf of Mexico area to be "rust free"?

When I bought this car in 2016, I went over it thoroughly with a paint thickness gauge and could find no evidence of body filler anywhere except for a probable accident repair about midway up the driver side door. While having repairs made (transmission and front suspension) the mechanics volunteered as to how clean and solid the car was underneath. Being a little surprised and having expected the worst, while it was on a lift having the front suspension replaced I asked to borrow a hammer from the shop owner. I then, with a bad attitude, proceeded to beat the crap out of every piece of metal that was exposed - trunk drop-offs, frame rails, rockers,  floorpan and as much of firewall as I could reach. My intention was that if there were any soft areas, I was going to go ahead and knock a hole in it so that I would know what repairs were needed. Other than some light surface rust - nothing - solid as a rock. I did find a small rusty area at the bottom of the driver front fender near the door/cowl area but nothing that needed immediate attention. That was 3 years ago.

 I recently discovered 3 small pin-holes in the driver rear quarter behind the wheel. Can't see these from the outside because they are in the black accent paint just below the accent moulding but can see light coming through when looking into the trunk drop-of. Front fender rust spot has gotten worse and will soon need repair. 

When i bought the car it came with a notebook full of detailed mechanical repair records covering 20 years but there was nothing mentioning bodywork. I know that the car had been in a minor wreck and had been repainted sometime after 2008 but none of that is in the records.

I guess my question is : If its not reasonable for the car to survive this long with no metal repair, how do I tell if floorpans, trunk, body panels have been replaced ?
It's entirely plausible, it all depends on in what kind of weather the car was driven and how it was stored. If it was a fair weather driver and stored in a dry garage, it could easily have next to no rust, even up here in the rust belt. Given the documentation you have, I'd assume that's exactly how it was treated.

 
First things first. You have to remember that rust is caused by exposure to moisture and air. If the surface has never been exposed than yes it could be rust free after 46 years. Most rust on older cars occur from the inside out. By this I mean that it occurs on the inside of panels where there is little or no type of treatment and rust through to the outside. We first notice it as a bubble under the paint with rust stains. Paint chips and scratches of course expose the surface and allow rust.

As far as telling what sheet metal has been replaced is not that easy. The floor area was a stamped out solid piece with no seems. If the floor pans have been replaced you should be able to see signs of this from underneath. The quarter panels, rockers, and roof can be a little harder to detect. Most of the time welds are only grounded on the finish surface side. I would look at all expose areas to see if you can see a weld seam where there shouldn't be one.

Depending on where the weld was made, you might not be able to tell without pulling interior panels. Others you might not be able to tell at all - patches on rockers or in the trunk above the gas tank. When is comes to under the hood most of the time full apron and firewall panels are replaced.

The cowl could have a patched inside by the air intake. This is one area that is rust prone. If the job was done right it will be hard to tell. you can pull the cowl vent screens and try to see if there is a patch on either side. You would have to get under the dash to tell. Also would need to pull the heater box to check out passenger side.. You could to try to see if the top of the cowl has been removed by the spots welds looking different or out of place.

It might be time for a full strip to bare metal. This will allow you to find all the rusted and bondo areas and make any needed repairs. If you plan on keeping the car it would pay for itself in the long run.

 
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Cars can be looked after in many different ways -- mine only has a tell tale layer of aged oxide underneath with no rot or rust to be found anywhere...yet is 48 years old .... my XK8 2002 model has more issues. It is astonishing how these can last. 

All the sills are original with factory weld spots 





 
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