Smooth running after 5 minute warm up. Clean tranny fluid, red not brown, no burnt smell. Check for underbody rust. Check that you can shift t-case into 4x4 while coasting (make sure that front hubs are manually locked first). Check for fuel leaks near the filter (passenger side firewall, rectangular box thing). Check the voltage meter. There is a small "tic mark" in the green area. That is where the needle should point. Get the current owner to leave it alone for a few days, then go start it yourself. If it starts easy, it's good. If you have trouble, might need fuel lines, glow plugs, Injector Pump, etc, etc. Let it warm up for 5 minutes. Shut it off, wait a few minutes, try to start it again. Should be easy - if harder than the first start, you have glow plug card problem. Drop your price a bit, but it's not hard to fix. Check around where the cylinder heads meet the block. Look for coolant leaks. After warm up, if it's warm out, there should not be smoke out the exhaust. Go smell exhaust. If it smells like coolent, think head gaskets. (common problem on these). Look at the harmonic damper from underneath. (lowest pulley, the one on front of crankshaft). It has an inner metal hub and an outer metal ring with 1/8" of rubber in between. Check the rubber for cracks and bulges. Grab the outer ring, see if you can turn it separately from the hub (you shouldn't be able too). If you have one, bring a metal marker. Mark a line across the outer ring to the hub. Take a test drive. The marker line should line up after you shut it off. If the outer ring has shifted, the damper is shot. It's not the hardest thing to replace, but if it's shot it puts extra stress on the crankshaft. These engines are known for breaking crankshafts. Check the "lift pump" (low pressure fuel pump) (low on front of engine, passenger side) look for leaks. Look in the cylinder valley with a flashlight. (remove air cleaner to see). Diesel in the valley is a sign that the pump seals are going on the Injector Pump. Look where the brake booster would be. You'll find a hydraboost unit. It is a hydraulic booster powered by power steering pump. Check it for leaks. Check all fluids. Check under truck. Look at axels, frame, bumpstops (rubber triangles that the diffs run into if you bottom out). If it looks like it's been abused, you might not want it. Test driving should show good breaks, easy steering that isn't super sloppy. Listen for bearing noises. Tranny should shift firm but not slam. Check coolant - should be fairly clean. These engines don't take overheating well. There are oil and tranny cooler lines on the drivers side fender / frame rail. Check them for leaks. Check the batteries. Should be clean, full of fluid, not corroded. You need good batteries. All I can think of for now. Good luck!
The next one is going to be a 5 ton, but this is a good start.
