Help: 2001 Tacoma 3.4L V6 Knocking/Tapping Sound

Hello everyone,

So I started hearing a knocking noise and so I checked the oil and it was full. I have done the following maintenance for other reasons:

- oil change with 5W-30 (mileage currently at 175K mi)
- replaced all 6 spark plugs (w/NGK)
- replaced all 3 timing belts (w/Toyota)
- replaced fan clutch (wasn’t engaging)
- replaced a/c compressor (was bad)
- replaced alternator (was bad)

I am aware some of these things wouldn’t cause knocking noises, I am just giving more information rather than less.

Does anyone have an idea of where to look next? Maybe a pulley is rattling?

Also, the noise doesn’t happen when starting my engine cold. Although, after it warms up and drops below 1k rpm the noise starts. I can only hear it when the car is at a stop either neutral/park or drive with foot on the break.

Hope to hear some feed back soon, thanks.

 

Video would definitely be more helpful, so everyone has more of a general idea what it sounds like. There are so many things that can knock/tap. My guess though is probably a cracked flex plate, take off the little cover on the bottom front of the transmission bell housing behind the oil pan, and you can look up around the flex plate to see if its cracked, you would have to take off the transmission skid plate though. There are other things that it could be, water pump, valve clearances, loud injector, etc.

 

Thanks for the reply, Jacob! See link for video: https://youtube.com/shorts/op5-JHogv_U?feature=share. Thanks again!

 

No problem, id definitely say check that flex plate, at least that's what it sounds like to me. If it is cracked, only replace with OEM flex plate and new bolts for it. Might as well do the rear main seal while you have the transmission out, so you dont have to worry about it in the future! The job in my opinion isnt too hard given you have the correct tools and time. Just wait for others to pitch in their ideas too, as it could be something else until you verify it isn't the flex plate. Keep us updated!

 

Sure does sound similar...

https://youtu.be/nwPhEMmDFEg

https://youtu.be/E5h7kCs8sKU

@bigizzy, pull the inspection plate and see if you can confirm any cracking. If you end up pulling the transmission (not a difficult job, just time consuming) to replace the flexplate/rear main seal, be sure to start with the black bolt when mating the torque converter to the flexplate. A transmission jack is a must-have for this job. Also, second the OEM recommendation.

https://static.nhtsa.gov/odi/tsbs/2014/MC-10109404-9999.pdf

https://youtu.be/P0n8ZsWhlL8

 

Thank you Jacob and Mike!! I’ll definitely go look into these suggestions. You guys are awesome, I’ll let you know what I find out.

 

If you aren't already familiar with it - Remove the inspection plate by removing 4 bolts holding it in place. For what you are doing, not necessary to remove the bolts securing the torque converter. Just slowly turn the crankshaft so the torque converter/flexplate turn so you can visually look for any cracks. If you don't see anything, it'll be time to make the decision whether to pull the transmission as cracking may not yet be visible in that inspection area.





Red circles are the 4 bolts holding the plate/cover in place. The yellow area does not have a bolt.

As you turn the crankshaft, you're looking in the blue circled area of the flex plate for any cracks. If you find any at all, its time to pull the transmission and replace the flexplate with an OEM plate.

Good luck.

(stole the pic from another thread thx charry323)