Should I change the whole engine for a damaged piston?

A Subaru '09 with 60.000 miles has a damaged piston. The mechanic first said that I need to get a new engine for 5 grand. Now he is looking for other options
This car can be sold -in good condition- for about 12.000 but without the engine is worth 4-5.000 should I put a new engine to a 4 year old car? Why can’t I change the piston and fix whatever other damage it might have?

Before anything can be determined which route to go, the engine needs to be disassembled to determined what caused the piston to fai,l and what other components were damaged.


How is the piston damaged?

Are there any pieces of metal that have scored the cylinder wall?
Or if the piston has a hole blown through it, are there any metal fragments that found their way to the bottom end?

Pistons don’t just break, they take lots of other parts with them, usually, like cylinder walls and bearings. And like the other said, ask WHY it broke - it is very important to know.

I had a 1990 Ford Aerostar. The vehicle was under warranty, fortunately. At any rate, one cylinder head had a hairline crack. The entire block was replaced as well as one cylinder head. I thought the service department might just hone the cylinder wall and install a new piston, but the service manager said that Ford’s policy was to replace the whole block if there was damage. I agreed with Ford on this one. In your case, I think I would go with the replacement engine.

Since everything else has been covered, I might wonder if this particular Subaru was a turbocharged model running on low octane and in the boost quite a bit…

A damaged piston is moving inside the cylinder block and can gouge a groove in the cylinder wall. That means replacing the piston is only part of the repair. You also have to smooth out and round out the cylinder wall. This can be tricky and requires well calibrated equipment. If the motor has to be pulled out the car, then you might as well get a rebuilt short block (restored cylinders, and matched with new pistons and rings) which will cost less in the end.

Your mechanic and I have similar opinions. You don’t want either one of us to rebuild your engine. Yes, I would prefer to tear it down and look around but that costs money too, and if I “forget” to follow the instructions, you’re walking and I’m losing time and money.

Whatever the choice, it has to be fixed because it’s worth a lot more that way.

Others will disagree, but as a consumer and not a mechanic, I never let anyone open up an engine anymore. Only question would be why and short block or long block.

I share Bing’s concern about never letting anyone open up an engine of mine anymore.

There are too many subtle things to worry about when rebuilding an engine which were “common knowledge” years ago when more engines were rebuilt. Mechanics with good engine rebuilding skills are growing harder to find.