After ~87 IDI's came equipped with the more desirable solid state glow plug controller. Earlier years sucked because when they'd fail the GP's would stay on and it would burn them out. I'm still not a fan of the controllers regardless so I converted mine to a manual push button for simplicity.
Any of the turbo kits are good imo. Factory kits made by ATS were an option from 93-94 and they were good other than they had the less desirable 2.5" outlet. ATS no longer sells the 3" conversion but I think R&D offers one now. Its been said the turbocharger in the Banks Sidewinder does have a few pieces that are hard--some say impossible--to find. I don't think I'd turn down a truck with a Sidewinder kit but it would make me a little nervous.
Leaks. I'd plan on resealing the oil cooler relatively soon. It's a messy job for sure, but it's not terribly difficult and it costs about $45. You'll want to change some o-rings in the fuel system soon after buying as a preventative measure. Its not hard and it's dirt cheap to do. I can talk you through that one.
There are no exotic, weird, outrageously expensive or unobtanium parts that I'm aware of. If the motor blows yes that will cost a lot---$4k or more for a Pro-mar. However all the normal wear and tear components are very affordable, plentiful and usually pretty easy to change/replace. Fwiw the injection system is especially affordable compared to modern diesel engines.
As I said before most of the stock gauges are worthless. As in worse than dummy lights. Not a huge deal just kind of annoying. You'll want to add an aftermarket temp gauge for sure and hopefully the fuel gauge/sensors work or you might have some work cut out for you.
You may want to budget for a new aluminum radiator. There are a couple options ranging from $200 on up. The old brass units usually up there in miles and the parts store brass radiators suck big time on these trucks.
Check the rear drums for wetness. The hubs seals on these are sorta interesting.. I don't think I'd call them unreliable but they're about $50 a piece and you'll need a special hub socket (have one if you need to borrow it) to change them. Not a deal breaker just a messy job.
Red flags for me are:
-Autolite or Champion glow plugs. I've had serious headaches with these in the past on other vehicles. They will swell up on the ends and it can be extremely difficult/nerve racking pulling them from the heads. Not a deal breaker just be warned if you buy a truck with them in it cross your fingers and get them out asap.
-Excessive smoke in any color. White and/or black puffs are normal during startup, black is normal under heavy acceleration or load but you should never see excessive black, blue or white smoke while cruising with a warm engine.
-The dual mass flywheels will explode if pushed beyond their wear limit. At this point in time most have been replaced with single mass because they're cheaper and more reliable but you never know. It's normal to hear the ZF5 rattle and groan but if it sounds like a jar of quarters being shaken under there chances are it's time for a clutch.
-Earlier model IDI's. 83-85ish could have the weird (short/wide) radiator size. They're kinda hard to find. Early blocks have been know to crack near the block heater. Those issues were resolved later on.
-I have no experience with them so look into this a bit further, but I've 'heard' the A4OD overdrive automatics are troublesome and expensive to 'fix'. Theres a million of them out there so it could be just hearsay.
Anyway you can't go to a stock auction or farm yard without seeing at least one IDI. Most have been overworked and neglected their entire life. Has to mean something right?
EDIT: Constenoga diesel and R&D IDI performance are the go to places for upgrades, parts and performance. Oil burners.net has a wealth of information. The tech articles there are outstanding.
