I don't know if later-generation Fords have this issue, but yesterday I discovered why mine has a big rust spot in the rocker panel, just forward of the driver's side door, on both sides of the truck.

I decided to replace the heater core yesterday, since it's getting cooler and mine was bypassed by the previous owner. After spending the day doing that job, I can see why he decided not to do it himself.

Replacing the heater core on a truck without air conditioning is a major pain in the neck. About five hours of work. But I won't go into that; there's good information around on how to do that job, thankfully.

While I had everything apart, I discovered that the previous owner had parked the truck under a long-needle pine tree, probably for quite some time. There are vents in the driver's and passenger's kick panels, and I had to take the passenger one off to get at a bolt to remove the heater core shroud.

The duct was full of dirt and pine needles and evidence of a packrat ...

Water has been getting down in there and just sitting in the mess of dirt/pine needles/whatnot for years and years. Not drying out, just slowly rusting the rocker panel from the inside out.

It's not difficult to clean it out with a shop vac. I did so (and on the driver's side, too, even though that duct panel is much harder to remove since the emergency brake pedal interferes).

There was an amazing amount of stuff in there. I'd say several pounds.

Take the time some weekend to get in there and clean it out, especially if it looks like you're starting to get rust there. It's too late for my truck -- I'm going to have to replace both those body panels eventually -- but it may not be for yours!

 

All these trucks are susceptible to the calamities you describe. I have experienced some myself. The damage accumulates exponentialy and costs time and money to repair.

Annual or semi annual routine cleaning of these trouble spots is well worth the effort.

Maybe we can come up with a check list of preventive maintenance here that will help new and old owners alike.

In addition to the kick panel ducts described above and the cowl area at the bottom of the windshield I would suggest keeping an eye on the area where the radiator support mounts to the frame.

Water and dirt get trapped there and it is pretty much out of normal maintenance sight. I was surprised how compromised the mount was, mostly on the drivers side. Some patch and weld work saved over $300 for the replacement. Regular cleaning of the area and the occasional rust convertor and chassis black will go a long way.

Same thing with the coil spring upper mounts in the rear. GLR clued me into this one and he is right.

Reps flanin.

 

for those of us who keep those at least halfway clean, driving on the highway with those vents open will often blow out the little bit of material that has accumulated there and prevent large buildups.

i've dealt with related problems on dodge caravans, except that on those the gunk accumulates in a plastic piece, clogs the drain, and flows out into the heater ducts. many owners install window screen on/under the grating to slow down the entry of leaves and needles. it might be productive to try the same thing on a ford

 

Most heater fires are caused by that same buildup of debris and "stuff" you are describing. Removing the Heater Fan, and the Blower motor resistor and cleaning behind them is also good practice to keep.

The 1987-1996 trucks had their cowl panels redesigned to help eliminate stuff getting into the cowl, and heating system. Good news is they will work on our 1980-1986s if you have concerns of accumulation.

 

I had a very similar issue with my truck Flainn. I ended up changing my cowl panel out for a newer one from an '87 model. it has the same body lines, except instead of slots it has holes. So far, I have found that it keeps most all of the leaves, and a great many of the needles out. It's not perfect, but it is a great improvement.