What would cause the two middle cylinders on my v6 to have no compression and the other four cylinders do?

Question

Mazda 6 3.0 V6. Cylinders 2 and 4 have no compression and the other four do. What would cause this?

Answer 1

This could be caused by any number of problems. The most common are probably:

1. Stuck or burned valves
2. Blown head gasket
3. Burned piston
4. Damaged piston rings and/or cylinder wall

Is there any other history of this vehicle that might give some more clues?

But before you do anything else, please double-check your compression tests. I find it odd that there are two cylinders with ZERO compression.