timing chain questions

[munkee]

squint Dangit, the noise I had previously from a bad timing chain tensioner is back. What causes the tensioner to go bad? Could slack in the chain be making all that noise? It sounds a lot like the chain on a bike when you backpedal. The old tensioner was fully extended and wouldn't compress until I took it out and worked with it for a couple of seconds. I didn't replace the chain when I did it. The noise usually stays consistent with the rpm's and it will usually quit after a minute at idle or if you shut the car off and start it again in a couple of minutes. On startup it will make the noise for a second and then go away. Could it be an oiling problem? What would cause the tensioner to stay fully extended? I couldn't even get the old tensioner to compress by turning the exhaust cam with a wrench but it would quite easily after I changed it. Am I maybe looking in the wrong area? What else could cause that kind of noise. I just replaced the rod bearings and I am pretty sure I did them right. What is the torque for the rods again? If I forgot to tighten down the oil pickup tube (and I am pretty sure I didn't forget) what kind of problems would that cause? No codes and no dash lights. Hopefully I can get this figured out before it causes any damage. Thanks.

 

[Yamaha V6]

If the tensioner went bad, the chain has slack, which a) causes the clack as it slaps against the chain guide, and b) causes a jerking on the chain every time the cam lobe gets beyond perpendicular & the valve spring is free to rebound. Over time the chain stretches if the tensioner is not replaced.

If you replaced the tensioner and the chain has slack, it may still slap. Usually you can verify the chain tension before you button it back up again, and change the chain if necessary. Chains cost about $50 ea, IIRC.

 

[DavidT]

the noise is back?
This does NOT encourage me... why do I like these cars??? headbang
Hopefully tomorrow night I can get under my valve covers (for my very first time eek! )
How did your cam lobes look?

 

[munkee]

David, I hope it goes well for you. My cam lobes looked pretty good but that made me think of something else. Before I put the engine in the car, I did the full 60k valve shims etc.. I didn't even think to check the clearances on the replacement head. How loud can a shim or two out of spec get?

 

[DavidT]

munkee,
Got any updates???
I am still crossing my fingers with auto-rx (I am in the middle of my 2nd treatment) Some days the noise will disappear, and I think, "WOW!, I didn't WASTE $50 on this Auto-RX", but then the nasty noise lets me know that I am wishful thinking...