2.4 Low compression, knock in head

**anticon** · 04-07-2013, 07:50 PM

Hey All,

A few months back, my friend broke her timing belt while driving he '02 2.4. She had bent a couple valves, so I found a real nice used head for cheap and cleaned it up and installed it.
Anyway, she's recently had some cooling system problems, and it likely ran too hot for too long. Now there's a terrible knock or clank kind of sound (much louder and more aggressive than lifter tick) which seems to be coming from the top end (cyl. 4 side) only under load (never while idling or even revving, though I've been able to replicate it under hood by rapidly hitting the throttle). The only code it throws is for a misfire in cylinder 4. Just to be sure, I ruled out any ignition issues by swapping components. I pulled the rocker arms from the intake side and couldn't find anything out of order (bent components, worn lobes, etc.).
I guess that's all kind of irrelevant - I did a compression test and got around 130 psi in cylinders 1 and 2, and only 60 psi in cylinders. I'm thinking the heat may have burnt up a couple piston rings.
Just wanted to see if anyone has any suggestions before I have to tear this thing down again...
Thanks in advance for any replies!

**kylecanthurdle** · 04-07-2013, 08:34 PM

usually when a car overheats itll take out the head gasket......could also be a cracked head and/or block. while its running pull the reservoir cap off but keep the hose in the coolant. if bubbles come out then that means the exhaust gasses are getting into the coolant somehow. give that a try and see how it goes.

**anticon** · 04-18-2013, 01:20 PM

Thanks for the reply. I ended up finally getting around to tearing it down. I had considered a blown head gasket, but it just didn't seem right to me - but the proof is in the pudding: