Timing Chain Brand?

Do you have any indication that the timing chain is in need of replacement? It is not a routine maintenance item as a timing belt would be.

It would also be quite challenging to replace in the cramped underhood of a Gen 1 Prius. Out of curiosity, I once tried to position a hex bit in the timing chain tensioner access plug just to see if I could do it, and I could, but there was blood on my hand. Reinstalling the timing chain cover would require precise application of the form-in-place gasket, and proper placement and tightening of the cover, all in that cramped space, with no bumping or contaminating the bead, within a small number of minutes. It would be a much easier job with the engine removed from the car.

If it were mine, unless there is a known problem with the chain, I would spend 15 minutes replacing the serpentine belt, and call it a day.

 

I’m with Chap. I have one over 300,000 miles and two pushing 300,000 and aside from the fact that I have not heard any noise indicating a need to change the timing chain, I’ve never heard of it happening on one.

 

My old Gen 1 started doing that too, around 198,000 miles.

Never did figure out why. Had a close encounter with an eastbound Dodge Dakota 36,000 miles later, which made the mystery moot for me.

Timing chain was one of the possibilities a mechanic had suggested to me, and valve clearance was another that I looked into. Because of the way the 1NZ engine is built, dropping in a replacement engine would have been less fuss than either.

 

Try changing the plugs first and look for signs of a leaky injector. My sons was doing some rattling, in the beginning it was just at start-up. If you see signs of fuel leakage around then you’ll need to chasing out the rubber seals.

 

The details can be followed in the thread I linked above. I did not find anything that stood out as a smoking gun.

On the 1NZ engine, valve clearances are easily enough checked. It's only if you see a reason to adjust them that engine replacement becomes the simpler prospect.