There's no question Ford had a winner with the Super Duty 7.3L diesel, made from 1999-2003. Here are a few tips to think about when looking for a used one. Take it from someone who's owned one for many years!
Automatic Transmission-The earlier models had transmission problems. The transmission would run hot and burn up. Ford had a pro-active service bulletin and would fix the problem for free. The 1999 and some 2000 models did not have transmission cooling lines to the radiator, so Ford replaced the radiator, added cooling lines, plus a ton of other small parts. If you find an older model that has not had this change, it will set you back several hundred dollars to do so.
Water Pump-Coolant puddles under the vehicle after being parked. The seals go bad in the water pump and coolant leaks out of the water pump weep hole. It is a pretty big job to replace the water pump if you've never done it before and will cost $200-300, since you'll probably want to replace the hoses, coolant sensor, serpentine belt, etc. Plan on spending a lot more if you have a repair shop do it.
Fuel Drain Petcock-Fuel will leak from the fuel filter housing. The "O" rings in the fuel petcock located on the back of the fuel filter housing will need replacing. The repair will only cost a few cents and about an hour of your time to fix.
Rear Brake Calipers-The rear brake calipers stick and the rear pads will wear out prematurely. If you don't catch this in time the disc brake rotors will need replacing also. In 120,000 miles I had replaced the rear calipers and pads twice. If you do it yourself and use discount parts it will run you about $130-150. If you have a repair shop do the repairs prepare to pay 2 or 3 times that.
Starter Motor-At about 100,000 miles I thought my batteries needed replacing. The starter got progressively more sluggish as time when on. Eventually nothing happened when I turned the key. Turns out the brushes in the starter had completely worn out. I took the starter to a shop and had it rebuilt for half the cost of a new starter ($85), and still got a lifetime warranty.
Camshaft Sensor-These go bad at about 100,000 miles. When it does you'll know it. You'll go from running nice & smooth at 70 mph to not running at all. The replacement camshaft sensor is about $30. Get one from the Ford dealer. My truck was out of warranty and Ford still replaced it for free. The ones from the discount auto parts stores are a couple dollars cheaper, but they are not as good. Before I went to the dealer, I tried a 2 different sensors from the discount places. One made the truck hard to start, the other would start okay but it ran rough. Just get one from Ford and save yourself the trouble.
Speed Sensor-If you happen to test drive a model with non-working cruise control, the overdrive light flashing, and a non-working speedometer below 40 mph, don't let that be a deal breaker. The culprit is a $30 speed sensor, located on the rear axle. Takes about 15 minutes to replace.
Tires-A set of good tires for a dually will set you back $1200, about $800 for a standard model. If you find a nice example with good rubber you will be several hundred dollars ahead.
Fuel Mileage-These trucks are known for their excellent fuel mileage. Mine gets 23-24 mpg on the highway.
Modifications-A lot of these trucks have been modified over the years. Exhaust systems, turbos, computer chips, lift kits. Unless you know a reputable shop has made these modification, beware of these vehicles.
