The dealers usually and often will want you to agree that they’ll bill you for up to 5 hours diagnostic time(refundable if they accept the claim under the warranty).
Here is how you can do it in 30minutes or less.
Remove ignition coils and spark plugs.
Use horoscope (Inspection camera)
Stick it in every cylinder and check the valves
Use 24mm socket to slowly rotate the engine, often you can feel that engine rotates too easy (it’s a bad sign-no compression). Using borescope, check if the valves move while you turning the crankshaft – you will see the pistons going up or down. Bring the piston up to or as close to TDC as possible (if you feel the strong resistance while turning, stop rotating) and see whether the valves are closing or not. If the valves are fully/almost open and making contact with piston(s), the valves are bent and the cylinder head has to come off for repairs before you can replace the timing chain tensioner, chain, chain guides and the sprockets too.
Whole inspection took me 30 minutes with plenty of picture taking,
As you can see from the video, all the inlet valves were open, even when pistons were moved up while rotating the crankshaft.
Of course you can do compression test if the engine rotate freely (to confirm the engine is mechanically sound). If not, don’t force it, you don’t want to cause more damage to the engine
The bottom line is,
no one should ask you to pay for 5 hours time when the diagnosing fault takes 30 minutes.
You only need to know that there is 1 valve bent and the rest of the repair process is the same, since it’s cheaper to fit a brand new cylinder head than replace the valves, guides and the rest that’s broken. ...and as for the pistons and the cylinder bores? The borescope gives very good insight what conditions pistons and cylinders are.
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