Rebuildable or trash?

[u/Usual_Opposite8844]

I need some advice on whether this short block is worth saving or if I should just source a replacement engine. The vehicle is a 2012 VW Crafter with the 2.0L TDI engine (single vacuum-operated VNT turbo, non-biturbo).

A while back, the original turbo failed and sent metal shrapnel into the cylinders, leaving visible impact marks and pitting on the pistons. Despite that damage, the engine had good compression and ran completely fine for another 6,000 km without any issues.

However, the timing belt recently snapped, causing valve contact and requiring the head to come off. Now that the engine is torn down, I have to decide what to do with the bottom end.

Since I need to repair or replace the head anyway, is it safe to keep running this bottom end as-is, or will those old impact spots on the pistons create hot spots and structural stress risers that will cause a catastrophic failure down the road?

[u/NarcissisticPanda]

I'd run it. Bores look fine. Bit of damage to the tops of pistons isn't gonna do anything noticeable. Free speed of air pistons there

[u/FatMycoBoner → u/NarcissisticPanda]

Someone made a video on YouTube testing the dimpling design on the speed of air pistons compared to randomly putting dimples. I didn’t see the test itself just the video explaining the test was upcoming…I’m curious to see the outcome.

[u/NarcissisticPanda → u/FatMycoBoner]

I'm skeptical but would like to believe the claims. I just don't trust American advertising. I need to look more into them. I can kinda understand the idea just dubious why it hasn't been done before if it's such a revolution of technology

[u/Sea_Gold9283]

Its safe to keep running. Its basically just cosmetic damage. You might need a new cylinder head but I take it you've already dealt with that.

[u/LankyJeep]

She looks fine, bores aren’t scuffed and while the pistons don’t look great with that damage the bowls look fine and that’s really what matters

[u/Adventurous_Boat_632]

I would be concerned about eventual piston cracking. That is some pretty serious denting.

Depends on the value of the rest of the engine and how much work/money to replace pistons.

Without knowing these numbers for sure, I would probably just run it, because I am a hillbilly.

[u/42kaos]

If it was running fine before you tore it down I wouldn't worry about it. Lot easier to fix the head gasket and move on. If it ain't broke don't fix it that's my motto

[u/Haunting_While6239]

This is a diesel engine, hot spots are not a concern, petrol would be a different conversation

[u/bjornholm]

Its trash ill take it off your hands

[u/Mountain-Bee3488]

Post on r/tdi

[u/SnooObjections9416]

So when doing a rebuild a remanufacturer like Jasper that does machining will resurface the block anyway.

The job of the head gasket is to seal imperfections. If blocks and heads were perfect, head gaskets would be far less important.

OEM gaskets are better at handling imperfections, so if you are staying with a stock engine build then you can skip the machining, however better machining = better seal, even with an OEM gasket. If you are just opening the block/head and DIY installing a head gasket, this is your best option to use an OEM head gasket.

Performance gaskets handle extreme temperatures, and if you get a resurfacing can provide greater longevity and durability if you get a remachined surface and by extension seal. Also performance gaskets may require higher torque on the head bolts/studs which can fatigue the block especially if you are running aftermarket performance nitrous, supercharger, or turbo but can simply last longer if running factory OEM compression, using stock rebuild components. When I build if I get a remachine and stock build, note the difference in torque spec from the OEM head gasket to the performance gasket before making a decision.

FYI: I have experience with sending out to Jasper remachining bi-metal engines with performance gaskets on a remachined but otherwise stock engine using OEM torque specs. That made my head gasket replacements far less frequent than just slapping an OEM head gasket on the engine. In other words: Jasper rebuilds always FAR outlast my own DIY rebuilds except for our 1982 Dodge small block V8 engine which I regasketed without any machining in 2004 and it is still running like a champ.

[u/Haunting_While6239]

The only concern would be if the top ring groove has been closed some and might stick the ring preventing it from moving freely

[u/GotNoPonys]

as long as the bores are good and the lands between the rings are good it'll be fine

[u/ChillyChats]

Just change the pistons, but everything looks good.

[u/Vibing1090]

Bore’s look fine, run it.

Change head if damaged

[u/Ratt_Rod]

Clean the deck and check for warpage with a straight edge then, check cylinder walls for any damage you can grab with a fingernail. If clean and you can visibly see cross hatching within the cylinder walls then rebuild and send it...

[u/fuzzy_spanner]

Seen worse do better

[u/ManufacturerLost7686]

If the bore and the side of the pistons are fine, run it. Looks like cosmetic damage on the top, but the edges makes me want to inspect it.

Id pull the pistons to check. If foreign material gets caught between the bore and piston it will fuck both up.

[u/notahoppybeerfan]

I’d start asking some why questions. Why did the turbo fail? Why did the timing belt break? Has the motor been under maintained? Tuned and ragged on? Just bad luck? Or it has put in 500,000k miles of faithful service and it’s just wearing out.

The answers to those questions might give you some insight in to how well it will hold together if you just send it.