If timing chain stretches, doesn’t the chain tensioner expand?

The timing chain does not actually "stretch" much at all. The metal components that makes up the chain is not vert ductile and will not actually deform much. It it the lack of proper lubrication and/or abrasive particles or detritus that wears the space between the components that causes the timing chain to lengthen.

The tensioner applies pressure to maintain a degree of pressure to keep the chain in contact with the timing gears but does not reposition the space between the gears. So, the only way to resolve your issue is to replace all of the timing components including the chan, the gears and the guides.

More frequent oil and filter changes would have delayed the onset of your particular situation.

 

how many miles on her?

 

Intergeneration 3 I wouldn't be banking on this. How many miles are on this vehicle let's start somewhere that we need to start In most Toyota's that I've owned over the last 47 years The timing components generally outlasted the car very few Toyota engines I've had to replace timing components on very few and I'm talking about things seriously out of spec making noises and ticks and all of that.

 

i wonder if the knocking sounds might be egr or head gasket

 

Bingo

 

Wear ("stretch") lengthening of the chain with mileage gradually throws off the angular relationship between crank and cam sprockets. Up to a point, the tensioner's job is to take up the resulting increase in slack on the slack side of the chain. How loose is your chain?

 

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This is a case of dual threads on the same subject. In his other thread he shows the chain which does appear loose. Op should avoid doing this so continuity is maintained. Probably a good idea to change the timing related parts. The tensioner could be the issue as well as chain wear.

 

A good moderator would have fixed that.

 

A good member has the option of clicking Report and considerately asking the moderator to do that.

 

Once two threads get going it becomes nigh impossible to merge, coherently?

 

The moderator has to be coherent and make necessary edits.

 

It's like the old gag about the two hikers and the bear.

The merged thread only needs to achieve more coherence than the original hodge-podge of separate ones.