Well effectively the only things likely to cause low compression readings are basically:

Inlet valves not sealing
Exhaust valves not sealing
Head gasket blown
Pistons melted
Rings broken up (just worn out wont do that)
Block cracked
Head cracked



Given the fact its two adajacent cylinders and they are dropping to the same value, that makes it seem likely they are ending up connected together, so either head gasket or block or head.

Of the 3, the one that sounds most likely to be effected so much by heat is the block, but this really is guesswork without more info.


First thing I would do is a leakdown test, if you do it with the cams removed it will mean that you can see if the air from cylinder 2 is coming out the plug hole on cylinder 3 when you do it, this would confirm its one of those 3 options in terms of connecting them together with a crack or block gasket.