Idi longevity

[Flylikeanidi]

My question simply is, with variance (rough riding, driving like a grandpa) no crank issues. the average lifespan of an idi engine with no mods, maybe a simple fuelling screw and cold air intake. Post with reasonable evidence.

[vanbcguy]

Many hundreds of thousands of miles is quite common. Overheating and / or timing belt issues are the usual causes of death. Neither should happen if you are maintaining your vehicle and using quality parts.

Low compression is the main sign of a worn out engine, eventually it will get low enough that you have trouble starting. Oil and air filter changes are largely responsible for maintaining compression - if you don't take care of the engine it'll wear faster than one that gets everything it needs, just like any engine.

[Dakotakid]

In asking a question like this, you apparently are assuming that all these engines are the same. They are not.

I honestly do not think the vast majority of true rebuilds will run as long as the oem short blocks. Why? Because the factory tolerances on the piston-to-cylinder bore were much more stringently held than that which most machinists will provide in the rebuilder-world.

I think the factory truly practiced the 0.0012 clearance on the pistons/cylinder wall. It is VERY hard to find a run-of-the-mill machinist who will follow suit. If you are not literally standing there breathing down their necks, they will routinely bore to almost 0.002 in. clearance............and, the wear limit is supposed to be 0.003 inch. They "throw-away" tens of thousands if not hundreds of thousands of miles of motoring wear with their cutters. Your mileage factor is sitting there on the mill or nearby floor in the form of little chips.

My longest-lasting engine was in a '82 Jetta. It made it to 435,000 miles before it refused to start from cold. However, it consumed oil (to a rather great degree) since 52,000 miles and I think that was due to the very hard moly rings Kolbenschmidt provided on their oem pistons.

Longevity is also contingent on your driving style: do you truly wait until the entire engine is up to running temp (not just the anti-freeze) before you throw full-throttle at it? Ever taken one of these apart and seen the scuffed pistons and stuck rings from early full-throttle application?

[wolf_walker]

What they said.

Also, you have to define longevity, a VW diesel, as is part of it's charm, can continue to be a useful tool long after it's pretty well "worn out".
Keep dumping oil in it, keep managing to get it started if it gets cold where you live, keep timing belts intact, and it'll run for ages.
Eventually they will have a "runaway" but even that can be mitigated to a degree with a few methods.

A better question might be how long do they last till they are annoying and/or embarrassing to live with on a daily bases.
To that I'd say, a very loose average given proper maintenance and habit from new, 350K give or take 50K.
With a headgasket somewhere in there and every other sort of maintenance procedure you can think of a time or two.

I also am strongly suspect of "rebuilt" motors, and completely due to the tolerances of the machine work and quality of the replacement parts,
not the builders ability so much.  A virgin motor in good order to me is something to be cherished and cared for still, or even more so, than in the past.

[RunninWild]

This question is impossible to answer. Doing proper maintenance and taking care of your engine, while respecting it will make it last a long time. How long is impossible to tell. Wear is going to happen even under the most ideal circumstances. Temperatures and regular oil changes are going to play the biggest factor in this. Metals fatigue, clearances widen and gunk forms as well as microscopic faults from manufacturing that can cause problems over time are going to effect its lifetime. There are too many variables to make a proper guess but its not uncommon to see 250-500k. In a lab under controlled variables in optimal condicitons I wouldnt be surprised to see over 1000k.

A better question to ask is there any design flaws in the idi platform that lead to premature failure. Other then the crank wobble and cranks forming in the head between the valve and in the pre-cups I think these engines are pretty well designed and can be counted on for reliable usage.