As far as the engine you might ask about the turbo, injectors, injection pump, glow plugs, harmonic balancer, and starter.

Make sure its cold when you start it, like sat over night atleast, glow plugs light should come on for 5-8sec. Crank it up with the hood open and check the upper Radiator hose, if you can't squeeze your fingers together and pinch it then it has a bad head or head gasket. Also check for a smoke cloud when you fire it up and make sure it doesn't puff smoke out the exhaust from a low hole (can also check that through the oil fill as blow by)

If it passes that then take it for a 15-20 min drive to get up to temp, should get up to 190 (if not then T stat is stuck), pull the oil fill cap and check for blow by (you dont want it to look like a freight train).

Check for leaks and general nit picking over condition next.

All of you um.. fine people.. crying about cracked mains and headgasket problems know the block was redesigned midway through production that took care of those issues right? Headgaskets only go when you overheat them, its the owners responsibility to keep an eye on the temp gauge. Any engine can be shelled with abuse, any. Injector life of 100k is not a design flaw that was intended and are supposed to be changed every 100k as MAINTENANCE not when they fail after 190k miles. 6.5s are a great engine if you take care of them and they shared a injection pump with 7.3L powered fords, you dont hear cries of junk pumps from that crowd do you? 6.5's being a bad engine is a bandwagon topic, everyone knows someone that grenaded one or dumped way to much money into one to fix simple issues not knowing any better. :humm:

Comparing a mid 90's indirect injected diesel to a 00's direct injected diesel is apples to oranges and a waste of bandwith. No idi diesel will ever compete with a new di diesel power wise. just not possiable. Want a good cheap workhorse? buy a idi diesel. want to race your honda buddies on the weekends to? buy a di diesel and get your checkbook ready.

humvee's run 6.5's, isnt it funny that an engine good enough for our military to send troops into battle everyday isnt good enough for forum warriors?

I love mine Just took a 700 mile round trip and got 21.26 MPG, and I have gas burner that don't get half that.

Erm..... they are good enough, if the price is good enough..

A 2wd manual can get good milage.... apparently a 4x4 auto cannot, because our regular cab gets 13 mpg. As far as reliability, ours is low milage (145k) but other than the PMD we haven't had any issues at all. You hear all of the horror stories, but short of catastrophic failures these motors are one of the most dependable daily drivers there is. They also start excellently in cold weather. They won't win many (or any) races, but they will pull anything you put behind them. We grenaded the rearend in a straight truck a couple of years ago, and (with the rearend completely locked up) pulled it 3 miles with our 6.5. The truck weighs in at about 43 thousand pounds, so that was no small feat.

TL;DR Good all around engines that don't really excel in any one area. Low milage and maintenance are EVERYTHING.

They change the 6.5 block many times over the years but never fixed it until navistar bought the rights in 01 and gm stopped using the 6.5.

IMO anything over 200k miles on the stock head bolts is asking for a head gasket problem but that said I've ran 2 over 300k with no issues and blew a gasket on a 3rd at 230k.

Injector rebuilds are cheap, change the glow plugs with ac delco 60g's or Bosch duratherms while you're in there.

94 and newer needs the pmd relocated.

My 95 k1500 z71 regularly got 19mpg and better on highway with 3.73 gears. My 94 K3500 single cab srw got 16 easily before I swapped the turbo and 18 highway after with 4.10's. My 93 K3500 service truck weighing in at 12.5k gets 13-14mpg highway. Trick is finding your trucks sweet spot to cruise in, might not be 75mph.

Looking at a 99' GMC 3500HD dump with 56,000 :humm: miles on it. Going to use your recommendations on what to look for before even thinking about this one..... I do like the "affordable" repair levels on this engine though. Any suggestions on what to look for on a low mileage vehicle like this?

By definition a good engine is one I would gladly install in a one engine air plane.

I would NEVER get in a plane that was powered by a 6.5L Turbo Diesel. NEVER

your definition maybe, but i would argue that our military rides to war on the backs of 6.5s every day and so does a large chunk of our fishing fleet. it is a very popular maritime engine and those people dont take dependability lightly. What idiot would think about putting a low rpm large block diesel in a plane? Kind of like saying i wouldnt run a 6.5 cause it wouldnt be good in a f1 car. :td:

Whoa with name calling their bub. It was a loose analogy, equating the well-known reliability issues of the 6.5 to a situation where all one really needs is reliability.

Stinks in here, to many folks

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