Evaluating a Diesel Van To Buy

When I saw the ad for a 1998 Ford Econoline E-350 Super Duty Extended Cargo Type II Ambulance Conversion Package 7.3L Turbo Diesel v8 I knew I wanted to check it out but I also knew that I knew nothing about what to look for. I work 7 days a week so I didn’t really have time either to locate a mechanic an hour north to check it out for me. So, I turned to the internet.

What follows here was mostly a word-vomit to myself, but these were all of the notes I took about things I needed to look for to evaluate the van.

See if you can get the VIN ahead of time and pull a vehicle history report online. There are a few sites you can see basics for free and many more that you can pay for more information.

I figured I didn’t know what all these repairs would cost, but by speaking a loud at what I found, I could use issues as a negotiator on talking down the price. (Un?)fortunately for me, I found almost nothing wrong so I paid almost his entire asking price.

Why Choose Diesel?

Well, really? Diesel chose me. I wouldn’t have normally leaned towards diesel because they require specific mechanics and special fuel that’s more expensive than gasoline… but, it just makes sense. As “Buying a Used Diesel Truck. Everything You Need to Know” on Driving Line states, “No other vehicle affords you the ability to lug 20,000 pounds through the mountains, carry the equivalent of a compact sedan in the bed, glean 20 mpg out of 4 tons of rolling mass or beat up on the local pony cars at the track without changing a thing.”



Before you start the van touch the exhaust pipe and make sure it’s not all rusty or brittle. If you wait until after strarting the van it might be too hot to touch!


Pushed down on each corner of the van. You want it to bounce once then return to normal. You don’t want it to not bounce at all and you don’t want it to bounce a zillion times. Jump on the back bumper and make sure the van doesn’t bottom-out.

Look at them and check the rods for rust, especiallay around the axles. You’re probably going to have some rust and that’s normal, but make sure they aren’t horrible.

A test drive will also help you evaluate the shocks.


Make sure the tires have tread, aren’t dry rotted (tiny cracks all around the side wall and tread), and overall are in good shape. If they aren’t, do a quick search online for replacement costs and keep that in mind.

Ball Joints

A ball joint is what keeps the tires straight up and down. Make sure the ball joints look completely straight. This isn’t a perfect method, but push or kick them and make sure they don’t wobble.


Get under the vehicle. Check bottom of engine for fluids. Look underneath engine area at the oil drip pan and bottom of the engine. Make sure there is no oil or fluids leaking or a dark colored sticky looking oil pan. Grease is probably fine. Oil, not so much. “Put your finger on the oil bolt and feel around. You should also look for oil leaks. If the pan is leaking that requires pulling the engine to reseal, a quick $3k right there.”

Park it on concrete if possible and also check for fuel, coolant or transmission fluid leaks. Note that if you used the AC on the drive then a water drip is totally normal. The internet can tell you how to determine what fluid is the one leaking.


Unfortunately, where I live in Ohio through parts of Pennsylvania are called the “rust belt” for a reason. The humidity here is a killer for metal. Really, to find a rust-free van I should be looking south and west. AKA I need to head down to Tennessee and visit Sue or James or to Florida to my grandparents and shop for vehicles down in their turfs. Same source as above: “Some surface rust underneath is OK (and is likely unavoidable when dealing with 10 to 15-year-old trucks), just make sure you’re not buying a vehicle with structural components that’ve passed the point of repair (i.e. bubbling fenders, brittle leaf spring shackles or hangers, dilapidated radiator core supports, etc.).”

I stole this image from them too

Be wary if the undercarriage looks freshly painted – sketchy sellers might paint over rust in order to cover up extensive damage.

Fuse Panel

If getting an ambulance make sure to inspect the fuse and other electrical panels. Dee if you can get inside the traces. In some cases, these have been trashed to make the ambulance road-worthy. All my lights still worked so I skipped this step myself.


If possible, witness a cold start.

Belts and Hoses

Loot for any wear or tear on the belts and hoses. Look for any dry rot / cracks / places where bubblegum has been used to hold things together. Look at the wiring and see if the harnesses look chaffed or otherwise showing undue wear.

Look for any damage or temporary repairs to hoses.


The battery terminals should be clean and free of rust/gunk. See if you can find a label on the battery to determine its age; they need to be replaced every so many years.

Glow Plugs

Diesel vans struggle to start below 40F. Make sure to test the glow plug system and the plug-in system.

Fluid Reservoirs

Pull the radiator overflow bottle cap off; if it smells of diesel you may need to replace the injector cups and that’s expensive.

Check for white residue on the coolant overflow reservoir/degas bottle (indicative of a blown head gasket). Make sure the coolantand overflow bottle level is full. heck the color; clear means it’s water (a big no-no that will rust out the engine). Appropriate coolant colors vary. IE Chrysler: orange or purple, GM: usually orange, BMW:blue. Search online for this real quick because a radiator replacement will run $750+.

Look around the oil cap and on the dipstick for any milky-white substance. If found, you could have a head gasket issue.

Wipe the engine oil dipstick on a white paper towel; it should be a light brown. Dark brown indicates it may due for a service soon but note that with a diesel engine the oil is probably going to be darker than you’re used to even if they just had an oil change. Black is bad as this means the oil has gone bad and probably means the previous owner didn’t keep up on maintenance. Running a vehicle on bad oil could cost you the entire engine ($3,000+). Don’t ask me how I know.

Look for silver-ish streaks or sparkley metal glitter in the oil as this indicates an internal bearing failure. How’s the oil level? Too high could indicate a vehicle burning too much oil and too low could indicate neglect.


I was a little skeptical when someone messaged me in a Ford Econoline group to ask me about my blowby. This is 100% not a term I’m used to. But, he said it’s a pretty simple test and that if the vehicle fails it I’m looking at $7-10k in repair bills. So. I’m totally going to do it.

“Let that 7.3 warm up all the way and take the oil fill cap off. Lay it back upside down over the fill hole if it will rest there and see if there’s enough air pressure blowing out to knock it off. If so there’s too much compression blowby. If it rests there and doesn’t blow off then it’s a good engine inside. It will probably steam or smoke when you pull the oil fill cap off but that’s not to worry.”


Inspect how dirty (or clean) the air filter is.

Don’t worry about the fuel filter because you need to replace that every 15k miles anyways so you’re going to replace that your first oil change right after you buy the van.

Test Drive

Engine Idle Time is Important

Diesels like to be left running. It’s often recommended in diesel forums to leave your van running when you are doing quick errands like a restroom stop. That being said, many, especially those that were once ambulances, have a high “engine time.”

One hour of engine idle time is equal to approximately 25 miles driven on the odometer. So in theory, if the vehicle was left running for 4 hours a day, it “ran” for 100 miles even though the odometer didn’t increase. For a vehicle like an ambulance turned tailgating vehicle, it probably has a high idle time. Per the same article referenced last paragraph, “a truck that has spent most of its life idling could have the equivalent of 400,000 miles on the engine but only show 100,000 miles on the odometer.”

I couldn’t find an engine ideal monitor in my old van, but check yours!

Check Engine Lights

Don’t accept any answer for why a Check Engine Light (CEL) is illuminated unless you can read the code yourself.

Most autoparts stores (AutoZone, Advanced Auto, etc) will run the code for you for free. Note, however, that mostof these places can’t run transmission codes.

Idle / Gear Selections

“Listen for any type of lope or miss at idle and when dropped into gear (could be the sign of an injector issue). If you hear any noises that bother you, consider it a worst case scenario and walk away.

“Pay attention to how long it takes for an automatic transmission to engage after making your gear selection.”

Make sure it shifts smoothly but note that per many of the forums I’ve read about 7.3L engines state that they “learn” your driving style about every 5,000 miles so it might smooth out eventually.

Does Everything Work?

Check all the windows for cracks.

Make sure all the doors lock and unlock.

Make sure all the windows roll up and down.

Make sure the front and rear wiper blades are working.

Check the heat system.

Check the AC vents.

Check all of the lights are working, high beams, low beams, fog lights, turn signals, brake and reverse lights. You might need a friend for this, but if you don’t have one with you, ask the seller to sit in and turn them all on while you walk around and check.

Questions to ASk

  • Have all the recalls been taken care of? (Get the VIN and you can double-check this yourself)
  • For a 7.3L Specifically
    • Has the camshaft position sensor ever been replaced? (failure can leave the 7.3L dead in the water)
    • Has it ever had its oil cooler, EGR cooler, EGR valve, injectors or turbo replaced? (all are prone to premature failure)
    • Has it ever been treated to new head gaskets (and hopefully head studs)?
  • Ask for service records
  • When did you buy the van and who did you get it from?
  • What did you use the van for? Heavy loads wear out brakes, transmissions, engines and the suspension but daily short driving on a diesel engine without ever pulling a heavy load can be tedious too.
  • Have you done any work or maintenance to the van?
  • Did you get any problems at all with the van?
  • How are the brakes, have you gotten them worked on?
  • Have you had any engine, transmission or other work done?
  • Have you had any starter, radiator, alternator problems?
  • I’m thinking more like ($500-1000 under blue book). Would you take that price in cash?

Sources and More Information

Everything above I stole from these two sites plus a YouTube video or two. 10/10 highly recommend reading both of these articles in additional to my notes!

The Sweaty Startup Cargo Van Buying Guide – this has additional tests that I didn’t write about above. Definitely also take this list with you!!!

Driving Line Buying a Used Diesel Truck: Everything You Need to Know – goes into more detail about the tests above and why they’re important and is generally just a great resource.

(post image source)

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