Friday Cold Morning Start.mp3I took a six hour trip over the weekend and my 2007 Fit Sport has been making a fairly loud knocking sound especially on cold starts. It fades once warmed up but is still there.

I did a valve adjustment about 6 months ago on it. Plugs are about 4 months old and I double checked they were tight based on another thread here.

Attached is what it sounds like from a cold start. What do you guys think?

 

Doesn't really strike me as an internal noise.....

Put a stethoscope on the compressor body and listen. It may be losing the pulley bearing. Sometimes I've been able to see the pulley wobble sideways in conjunction with the noise.

If it's not loud when you place the stethoscope there, probe around to find wherever the noise is loudest. Alternator, idler pulley, etc.



Remove drive belt and run the engine (BRIEFLY) and see if noise is gone, that would confirm it's a belt driven item making the noise.

BRIEFLY because the water pump won't be turning and it won't take long to do serious damage to the engine.



Spin the compressor pulley by hand, listen for roughness and rumble noise. See if the pulley has a lot of side to side play.
Spin the alternator and water pump pulleys too.

 

Other things to check:
exhaust system (joint between the header and catalytic converter pipe), shield mounting bolts
motor mount attachment to the timing chain cover

 

Earlier this week I pulled the serpentine belt off and I mistook my classic valve clatter for the noise (the noise wasn't as loud earlier in the week). Since you pointed me back to it I removed it again and sure enough the noise went away.

For those interested:
This morning cold start with belt on:
https://photos.app.goo.gl/FbufEm9t8yhZRz2X8

This morning cold start without belt
https://photos.app.goo.gl/XyzqQ7tWMwVPRxP76

This cold start with belt back on
https://photos.app.goo.gl/AfeUCnJdgSTd83Af9

Close up of AC
https://photos.app.goo.gl/fe8h5XqRpBQsatbs7

I checked pulleys for looseness and noise while off and other than a little ringing in the AC I didn't find anything. I'll doublecheck when I get a stethoscope but I'll probably order a new ac pulley bearing or assembly today.

Thanks for your help!

 

Sure sounds noisy at the compressor pulley

 

So I got a new NSK 35BD219DUM bearing from ebay for $7 and got to work.

I made a video for all the people with that weird clattering clunking noise and/or bad AC bearing.

Thanks for your help!!

 

Nice work on the video man, thanks for making the effort for other people who run into the same issue!

 

Excellent!

 

Great diagnosis as well as video tutorial!