>>15237874
almost any engine can be rebuilt/repaired. the question is is it worth rebuilding. if it cost more than someone wants to pay for the parts/service than it is a dead engine.

I'm not too sure about the engine, but I'd argue that something like a car's frame (I'm using a BoF as an example) is one of those that can suffer irreparable damage. That is, you must be doing some serious driving to twist/bend the frame in such a way that no matter how much money and time you put into fixing it, you've permanently compromised the integrity of it.

I'm curious to hear about the engine aspect from another anon.

>>15237874
Heat and friction.
And yes, ALL metal on metal contact points will wear away until we find a frictionless surface.
Bearings will always wear due to the heat they're subjected to, and the fact that it's just lubricated metal rolling across lubricated metal. The same thing happens with piston rings, except that's chromium on whatever metal is on the cylinder sleeve. Chromium is used because it has a metallurgy which allows it to expand and keep tension on the wall, preventing much oil / gas mix, but it will still wear away with regular use.
If you keep an engine up through regular service to 400,000 Mi, it will still be less powerful due to wear (lower compression and cam wear mainly) than the same engine at 15,000 Mi.

>>15237886
true as never really considered the fact that people might just want to toss it and upgrade if the car's already worn

>>15237894
Additionally, you get into the ship of Thesis paradox once you have to start replacing the block when you can't bore / re-sleeve the cylinder walls any further.
Up until then, money is the only issue.

>>15237894
But aren't the moving parts all replaceable? wont the non-moving parts last well and truly longer than 400,000 miles

>>15237903
*Theseus

>>15237904
Yeah, but when you have to start replacing the stationary parts is when you have replaced the ENTIRE engine.

>>15237907
Yeah i can get replacing the entire block being fairly pointless


well this entire thread has been surprisingly enlightening and useful, thanks

>>15237908
that's not sarcasm i just read that back to myself and it sounded extremely sarcastic

>>15237908
Sure. /o/ is a pretty nice place when the kids spewing about drivetrain configuraitons and sports cars they can't afford aren't around.

>>15237916
I'm a poverty stricken university student who just bought a new car and want it to at least last until i'm allowed to start working full time, i've done basic car repairs before but only like one rebuild ever

>>15237925
New new, or new to you?
If it's that TJ in the thread pic, it shouldn't be an issue. the 4.0 is pretty damn bulletproof.

>>15237925
car pic related? if it is then you should be fine. those jeeps are tough as shit.

>>15237929
That's a picture of a dog being hit by a Frisbee with the dog removed and is the only one with a car in it so i figured it might get more attention than lecture notes 8))

I own a corolla with 160k/kms from 1991

>>15237934
You should be fine. I think the only thing that might happen is a bit of oil consumption.

>>15237874
>Is there really such thing as irreparable damage from general use?
Yes, it's called Chrysler

>>15237874
rip doggo

>>15237874

connecting rod and other bearing clearances wear too much, oil pump clearances get too much, piston rings get worn, etc. eventually one day the engine starts knocking or whatever and its not worth tearing the entire engine apart usually

when a valve lets go and gets crushed by the piston or you blow a hole in the side of the block (seen that before, piston straight out of the block) its almost always time for a used one

if a connecting rod fails, it's often due to a seized bearing or broken rod bolts, but do rods ever break from metal fatigue?

You can fully rebuild and machine an engine about 4 times before it's past the limits for which you can buy standard bearings that will fit and before the bore walls gets too thin.

So a normal car engine can go about a million miles even if you machined it every rebuild, which isn't always necessary, so over a million.

>>15240307
ferrous engine parts should never break from fatigue if properly designed for longevity

>>15240327

you can always get oversized bearings and put sleeves in the piston bores though, some cars will go past without a rebuild. my uncle had a old F150 that passed 1,000,000km without a rebuild and a guy from Fiji i talked to has a Toyota Crown diesel taxi with 2,000,000km

>>15240279
I think ayy lmao got him.
>>15237933
You must be new

>>15240307
On an infinite timeline all materials will fatigue to the point of failure.
How long it lasts depends on it's design parameters. RPM and cylinder pressure in comparison to it's cross sectional area (weight) and type of metal (cost).

An OEM rod under OEM conditions will probably outlast the bores.

Rods can break from pressure, like from detonation, or boost. Heat, will weaken it, higher rpm will weaken it and can break it just like pressure, etc. all of the above can also break the caps/bolts.

>>15240341
but crank bearings only go to .40 under typically.

Then you can grind the crank to spec a bearing from a different crank. and reweld and machine the bores or sleeve them. but I was not including that to make it simple.

>>15237891
Or just irreparable rust damage from living in a rust belt state. When I worked at a dealership and old guy came in to get his timing belt changed on his second gen Jetta and the rust had eaten holes in the frame in a couple spots, and was considered too dangerous to drive. He was really sad about that, he had bought it new in 1990 and kept it running since then.

>>15240628
So no one informed him that it could be cut away and patched? Probably being stronger than it was originally.

>>15240642
I'm not familiar with frame cut and patch work, but how would it affect the surrounding areas of the frame? Wouldn't those areas need to be reinforced to have the same strength as the fixed area?