2000 S40 Low Compression Cyl 2 No Compression Cyl 3

[Chef Rhody]

Hello
Car started acting up a couple weeks ago. Rough when it's idleing and the CEL is lit and blinking, but when I get on it it seems to be much better. Acceleration is good and it rides fine under load. When I back off on it the CEL comes back on and starts blinking then as I accelerate it goes away and the car runs great. Misfire codes led to the obvious cheap fixes. Coil packs, plugs, No better. Compression check readings point to more and localized information
Cylinder 1 - 175
Cylinder 2 - 125
Cylinder 3 - 0
Cylinder 4 - 180

So there is the problem. No and low compression. in 3 and 2.
Possible culprits are a head gasket leak between 2 and 3, Burnt, chipped, stuck exhaust valve or a blown valve seal. Anything I am overlooking?
Wondering how and what symptoms I should look for in a leak down test. I am trying to diagnose and pinpoint the problem between a valve intake/exhaust issue (burnt, stuck, seal) bad rings or a possible hole in the piston. What should i look for in pinpointing this problem.

Your expertise is valued and appreciated,
Thank you
Chef Rhody

[alschnertz]

My guess would be a blown head gasket. I'd say a blown valve seal is unlikely.
How many miles?
I guess you could try a combustion gas analyzer to see if combustion gasses are getting into the cooling system.
Looks like you'd be pulling the head regardless of it being a head gasket or valve issue.

[Livens]

Not sure if it would be worth it at this point, but you should be able to find a mechanic that has a borescope. They can visually inspect the top of the piston and the valves for any obvious damage. Have you looked into the timing belt? Any chance that it slipped?

Honestly, unless you get really lucky, on a 2000 i think you are going to end up spending alot more than the car is worth to fix it. And unless you are going to pull the head and fix it yourself the labor involved would make swapping the engine for a donor the cheaper alternative in most cases.