Knocking in engine... loose timing chain??

If you want to see those marks aligned, keep rotating things until you do. On this engine, the orange chain links will align with their original marks every ninth time you see them go by (which is the same as saying every 70 full turns of the crankshaft).

So if you keep turning things until you've seen those painted links eight more times, and one of those times they were aligned on the marks, that's the way it should be.

If you've seen them go by nine times and never on the marks, something may be off.

Nine times or 70 crank revolutions are not the magic numbers for every engine, just this one. You can see this post and the one it links to for more on how to work the math out for any engine.

 

A broken timing chain guide is possible

 

To be honest, that sounds like a piston hitting the head, generally caused by worn bearings or the top coming off a piston. If you can get hold of one of those inspection cameras on a flexible stick that you can put down the spark plug hole, look for a mark on the top on a piston that is the reverse shape of the combustion chamber.

Just to rule out anything else, get a length of garden hose and with one end in your ear, listed to where the noise is loudest, an exhaust leak can be very deceiving sometimes.

Another method of tracking a mechanical noise, a length of steel rod, put one end on different parts of the engine and your ear close to the other end, or even touching behind your ear, the mechanical noise will transfer up the steel rod allowing you to pin point just where the noise is .....

T1 Terry

 

Is it loudest at the valve cover? I remember one member had a loose part on the valve train.

 

I was going to point out that the crank damper timing marks you photographed above arent really the same as the crank timing chain marks, but I see that you've now taken the whole timing cover off, which does let you easily see the marked chain link and the crank timing dot. It is also (just barely) possible to check those by only taking off the crankshaft damper:



You can see how the timing dot on the shaft is clearly visible, and the edge of the chain link you can barely see peeking out next to it is the one with the colored paint.

That said, I think if you have the crank damper at the 0° mark and the two camshafts are at exactly their specified positions, you can safely conclude the valve train is in time without worrying about the painted marks.

Wondering why on earth the oil pump needs to be timed has been kind of a running gag around here for a while. As far as I can tell, nobody knows. As with the valve timing chain, you could count the oil chain links and sprocket teeth and do the math to work out how many times you might have to keep turning the crank until the marks are back where they started.



"There's yer problem, buddy ... the oil timing was off!"

 

Is it throwing a misfire code? These engines make a crazy loud racket when a cop fails but that would throw a misfire code instantly. But yours sounds really loud and focused so maybe not.

Sure does sound like the top end or maybe like Terry said piston or maybe connecting rod slap. Sounds bad. I would do like terry says an get a borescope and look in the chambers. Could be the chain jumped and your out of timing and the piston is slapping the valves as this is an interfering engine.
And the chain may be slacky when there is no oil pressure.

 

Sounds more like a big end bearing excessively worn allowing the piston to touch the head, they run very tight tolerances to get the 13:1 compression so it doesn't take much to cause a piston to head contact. It must only be a touch because there doesn't appear to be any engine shudder and it would only occur on the change over stroke, the compression would hold it down far enough to not hit on the point of firing.

Possibly ran low on oil at some stage and that was enough to pick up a bearing shell momentarily and it's been chewing the white metal off the shell ever since ......

T1 Terry

 

The deciding factor which you may not know is has that engine ever ran out of oil so bad that the engine light came on to report zero oil pressure.
This happens alot on a Prius as its a pretty reliable car and and owners get complacent about checking its oil level. The zero oil pressure on a G2 for instance sometimes results in a blown piston wrist pin bearing t thing from the oil sump. In a G2 for instance this results in a rod thrown through the block usually piston #2 for some reason. But they make the same racket you are seeing before the rod takes flight.

The main reason people sell there Prius is it eat's alot of oil or the hybrid battery has reached retirement.

The sad fact is these little Toyota engines seem very difficult to rebuild. There's some magic happening at the assembly factory which is hard to replicate. Best bet is a used engine.