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The radiator on my 2001 Volvo v40 blew on the highway last week and the engine overheated.

I had it towed to my shop, and let them know the situation, and expressed concern of engine damage because it was running rough.

I was told it was just the radiator and it would be fine. After a week of back and forth with the shop and $3100 for almost an entirely new cooling system, they tell me that a valve in the engine is burnt and the engine needs to be replaced.

They're claiming they couldn't have diagnosed the burnt valve before the radiator repair. Is this true? I really don't want to be on the hook for $3100 and stuck with a car I can't use.

Edit: I guess the real question is, could you perform a compression test on the engine while the cooling system was disconnected/broken?

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    They should of done a relative compression test at the very least before doing any repairs. – Ben Jun 2 '18 at 1:01
  • Has it been running rough for a while? – Solar Mike Jun 2 '18 at 6:03
  • No, it only started running rough after it overheated. – Cooliemcawesome Jun 2 '18 at 15:45
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I guess the real question is, could you perform a compression test on the engine while the cooling system was disconnected/broken?

Absolutely.

The coolant line passages that flow coolant through the cylinder head and engine block are meant to be physically isolated from the combustion chamber(s). On a properly-functioning engine, a disconnected/damaged/open cooling system should have no bearing on the compression level that each cylinder is capable of.

A compression test should be able to pick up a burnt valve regardless of what the cooling system's condition is; the inability of the valve to seal in and retain air-fuel-exhaust within the combustion chamber will give rise to lower-than-expected compression readings.

In the case of a damaged head gasket or warped cylinder head, you might obtain different compression test results depending on the quantity (and subsequently pressure) of coolant in the cooling lines.

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the head can be warped and need to be machined ,i dont think replacing the engine would be needed unless you have no oil pressure or the engine is using or burning oil ,i have machined many heads for overheating and they all have worked fine without incident as long as there wasn't to much warpage on ohc engines which may require line boring or honing for cam journals ...im an automotive machinest

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