Hey guys
Been lurking for a while, but finally have given up the search.
2007 Cooper S
Timing chain replaced at 70k
Everything was good. 10k after timing chain, driving highway speed super knock sensor comes in. Car does not knock when at idle, only under load. Change knock sensor, no change. Took it back to shop that did timing chain. He says timing chain is good, but it now has low compression on 1 and 2.
Was thinking head gasket? But no water in the oil, car doesn't really smoke.
Any ideas?

 

Find out where the compression is going --- leak-down test? Maybe intake valves aren't seating, needs walnut blasting.

 

Thanks for the reply.
The knocking is in the timing chain area. From timing chain tensioner area or lower. Would valves cause this? Revving up the engine in park it doesn't do it, have to put it in gear and rev it with foot on the brake.

 

"Knocking" is very subjective, could be lotsa different things --- rod bearings, valve lifters / guides, piston slap, something on the accessory belt system. How sure are you the sound originates in the chain area? Can you capture the knock in a video and post it here?

I suggested a leak-down test to find out why you have "low compression", which is also subjective. What are the actual numbers, and was the engine hot or cold when tested?

80K miles on an '07 is pretty low. I've got 103K on mine, but it's been on jack-stands for a couple years, for mods and repairs. What's the reason for your low miles?

 

Pretty sure it's from timing chain area (75%). Way louder on that end of the motor, used a stethoscope type listening device. Sounds like something hitting, metal to metal contact.
Shop did the compression test. Supposedly 60 pounds on 1 and 2, put oil in cylinder and pressure was normal. Not sure if hot or cold. Didn't really miss or idle rough before this problem, or since.
Had low miles on it when I bought it a couple years ago. Car is in good shape, except for this issue.

 

Wet compression test with normal results implies rings are shot. Metallic noise in area of low compression implies piece of metal crashing around in chamber, possibly a chipped piston dome. Can you beg / borrow / steal a borescope to look inside the two chambers? Leak-down test might not be req'd if wet compression test is OK, but sure sounds like the head needs to be pulled off to fix it. Not likely to be a bad head gasket. Did you ever lose part of a spark plug in cyl 1 or 2?