I recently swapped my old 3.4l for a new JDM one because it was supposedly knocking. I recently put a screwdriver to the oilpan to make sure anything was sound and found that the same-ish knocking was still there. Not loud at all but same symptoms. ( only knocks when car is in gear or under load at idle). I replaced the harmonic balancer along with all the belts in hopes of quelling the noise- and for a few days it did. After this the noise came back. I swapped over all of my old accessories ( water pump- oil pump ect.) So I'm thinking one of the pulleys is making the noise. Does anyone have any experience with this issue. It's driving me absolutely insane

 

Welcome, the copy and paste makes it really hard to read.

manual or auto? Flywheel/flexplate bolts loose? Can you get a video of the sound?

 

auto. And no I can't :/ The noise is way too quiet to pick up well on a phone. Could be in the trans area but it goes away whenever I switch in new belts. I'm guessing the new belts make for more tension on the pulleys- which in turn makes whatever is loose stop smacking against the block. The only issue with that theory is that it only happens in drive- reverse or when the AC is on. Is there anything pulley/ pump related that is only activated under those conditions? I got someone to switch out the harmonic balancer but I'm not really sure if they switched out the bolt too so that might be the culprit. I read some threads where people said they've gone 500000-something miles with a similar issue but who knows anymore lol.

 

im not sure if anyones reading this thread but I took it to a mechanic and he said it's definitely not a knock. We did oil tests and the oil was clean- didn't cut open the filter though. At the time id driven around 500 miles on the engine so far so I'd assume if it were knocking the oil would have shavings in it. I also just checked the oil (500 miles later) by pumping some out of the crankcase and there weren't any shavings whatsoever. The mechanic also said it was one of the pulleys making the noise so it might seize up and lose timing. Should I be worried about further catastrophe or should I just drive it till she breaks?

 

I guess another, greater question of mine would also be: is it possible for a wobbly camshaft/ piston clearance/ any lower-end issue(that makes noise) to be fixed temporarily by the tension of a new timing belt/ drive belt?. I'd assume not but I'd rather hear it from a seasoned toyota person before I completely cross the possibility of bottom-end issues off of my list of anxieties.

 

The fan and alternator belts are different than the timing belt. But no, the exterior belts should not be making anything on the inside make noise.

I would take the belts off one at a time and run the engine for a short time to see if the noise goes away. Sounds like your mechanic narrowed it down to something in the front of the engine.. I would start taking it apart till I found the noise rather than risk being stranded somewhere.

the 3.4 is a non interference motor, so even if the belt snaps, the engine should be ok.

 

Have you got rid of the sound?
Edit: seems no.