Rust

[daverobev]

So. My 'beater' from a few years back is rusting. All the wheel arches show some signs, front driver wing/fender is bad. Bottoms of doors are starting to rust.

More worryingly, and I only really noticed this week, is that the bit along the bottom of the car, as it curves from the side to the bottom, which is hidden under a black plastic runner - to the "pinch weld" I think it's called - is actually rusting through. I found a hole in front of the rear wheel.

I don't think it's coming through into the cabin. Car is a Crown Vic, so body on frame. Car runs just fine. Mechanically it's good, AFAIK. Has ~260k km so plenty of life on that front.

My general question is... how do you know when a car stops being *safe to drive*? The door rust I am confident is not "structural" - the doors will still protect the occupant. Will I see actual holes in the floor of the vehicle before/as it becomes unsafe? Do I need to worry about what I guess are the equivalent of "cab corners" on a truck? Or at least.. under them.

I did get the car rustproofed last winter but it doesn't seem to have done any good. Or perhaps they just rustproofed the frame and not the edge of the car.

So it's the stuff under the door sill, not the door sill but if you go down/under from there, the stuff that is horizontal to the pinch weld. Danger/sad/don't worry?

If I can get a couple of years more out of the car it'd be great.

[Retired To Win]

In your shoes, I would get that vehicle mucho pronto over to a pro/mechanic/expert and get that person's take on where you stand and what your options might be.

Good luck.

[Thegoblinchief]

Get underneath the car and inspect the frame. Knock on it: does it sound solid or hollow? If you start detecting hollow spots, then you can worry quite a bit.

[HipGnosis]

Everything you describe is 'cosmetic', not structural. 

I think you wasted your money to rust proof it. It's rust proof, not rust stop.  You can't prevent what's already happening.

Crown Vics run forever.

[Melf]

As others have said, I wouldn't worry too much about the body rust issues if you can stand to look at them.  I would just be concerned about the condition of the frame underneath and all of the connection points from it to various parts of the suspension, drive train, steering, etc.  As long as all of that is still reasonably sound then I wouldn't be too worried about getting a couple more years of service out of the vehicle.

[Gone Fishing]

In addition to the structural integrity of the car, if you start smelling exhaust, it may be time for some repairs to prevent from being poisoned by the gasses.  Some sheet metal, rivets and sealing caulk would probably be enough for a cheap satisfactory repair.

[skunkfunk]

There are several holes in my car. Big ones. Huge. Worry not.

Mine is not body on frame, it is unibody, but there are no holes in the floor pans, rockers are a bit rusty, etc. Fenders, quarters, tail panel are a lost cause. Frame is rock solid.

I suspect yours is decades away from a dangerous amount of rusting. If there are holes in the trunk or floors, you can use fiberglass-ish stuff called Por 15 to patch it up somewhat permanently.

[acroy]

Everything you describe is 'cosmetic', not structural. 

I think you wasted your money to rust proof it. It's rust proof, not rust stop.  You can't prevent what's already happening.

Crown Vics run forever.

^^ this - Crown Vics are body-on-frame and that frame will take eons to rust the the point of being a safety hazard. Don't worry about it too much, just drive it and get full value from it.
FYI a proper rust treatment CAN stop further rust; as it seals off the metal from air. No oxygen = no oxidation = no rust. But it cannot turn back time.

[daverobev]

Ok thanks guys. Pretty sure the frame is fine. No holes in the floor or anything.

What holds the bottom of the car (not the frame) to the side of the car, then? If the bits from beneath the door where the body turns horizontal are rusting. I guess there are pillars and whatnot, plus all the metal at the front and back.

[HipGnosis]

There are several holes in my car. Big ones. Huge. Worry not.

Mine is not body on frame, it is unibody, but there are no holes in the floor pans, rockers are a bit rusty, etc. Fenders, quarters, tail panel are a lost cause. Frame is rock solid.

I suspect yours is decades away from a dangerous amount of rusting. If there are holes in the trunk or floors, you can use fiberglass-ish stuff called Por 15 to patch it up somewhat permanently.

Por 15 (and the many similar products) is not for patching rust holes.  It's for halting the spread of existing rust.   It might be a good idea for the OP to put some on his floor pan(s) and trunk floor.

[HipGnosis]

Ok thanks guys. Pretty sure the frame is fine. No holes in the floor or anything.

What holds the bottom of the car (not the frame) to the side of the car, then? If the bits from beneath the door where the body turns horizontal are rusting. I guess there are pillars and whatnot, plus all the metal at the front and back.

There are some relatively heavy pieces of metal going from the frame to the door hinges and latches - and on up to the roof.  They are between the passenger compartment surfaces and the outer bodywork of the car - only body shops ever see them.  They are part of the 'safety cage' (not sure if that's an official term) of the car.
If you don't have to lift your door to latch it, your cage is most probably sound.

[skunkfunk]

There are several holes in my car. Big ones. Huge. Worry not.

Mine is not body on frame, it is unibody, but there are no holes in the floor pans, rockers are a bit rusty, etc. Fenders, quarters, tail panel are a lost cause. Frame is rock solid.

I suspect yours is decades away from a dangerous amount of rusting. If there are holes in the trunk or floors, you can use fiberglass-ish stuff called Por 15 to patch it up somewhat permanently.

Por 15 (and the many similar products) is not for patching rust holes.  It's for halting the spread of existing rust.   It might be a good idea for the OP to put some on his floor pan(s) and trunk floor.

From their website:

"Among its many products, the latest from POR-15 is a complete floorpan restoration kit offering a combination of the classic POR 15 chemicals along with a sizeable offering of the two-part epoxy putty and fiberglass mat material. The fiberglass mat is used to span small rust holes that are too large for the putty but don't necessarily need welding. The hole is covered with the fiberglass mat, which is then soaked in POR 15 paint and allowed to dry. This transforms the flexible fiberglass into a rock-solid chunk of rust-proof flooring. This is a permanent repair, though it's not advisable to consider this a fix for those Fred Flintstone floorpans where there's more open air than sheetmetal; those are more often lost causes."

I used that on my trunk ten years ago. It is still holding, and that's after spilling a whole load of battery acid on it a few years ago that I didn't notice for two weeks before cleaning it up.