Help! Cold Start Loud Rattling engine sound
 

Did nothing to the car, engine rebuilt around 2000km ago, any clue what could make such noise? Only cold start, noises will gradually disappear as the engine warms up.

Please help me! Here's a video, pardon me speaking in my language.

If it's only happening on cold starts can you pin point the sound to your air pump? If so try unplugging it and cold starting to see if it eliminates the problem. Not a typical sound I'd expect from a worn out air pump but worth a shot.

Does it vary with RPM? You could have a spark plug wire loose. Try to localize it using a piece of wood, one end to your ear, the other end to various engine components. When you find the one making the sound, you'll hear it clearly through the stick.

ok i'll check asap and post a better/clearer vid from start.

been bothering me for quite awhile now.

yes the sound vary with rpm, the more i rev the more rattling sound it makes, until the engine gets abit warm (like 1/4 temp gauge), the sound goes away.

running on bhr and fresh plugs, 1000 kilometers usage (freakin' new).

Here's a better video :

Turns out even when the engine is quite warm, if i rev it up to 5-6k, the rattling sound is can be heard mildy. im quite worried. please helpppp..

The fact that it is increasing with RPM I'd definitely start by figuring out if it is just the belt, as the belt warms up it would explain why the sound goes away. If you can eliminate that the belt is not the problem than as you stated in your video, it is most likely one of the pulleys. Id start with the alternator pulley as it is obviously the easiest to access, if you can't pin-point the sound to be for sure from there then I'd say maybe the A/C compressor pulley (maybe something to do with the A/C clutch).

That's my internet 2 cent diagnosis!

Also, since the engine was just rebuilt, can you not contact the builder, or whoever put the engine in?

negative. let's just say that's not an option( alot of conflicts).

any inputs though?

Listening to it on a computer doesn't convey where the sound is coming from, so did you try that wooden stick trick? You need to localize it. I don't *think* the timing is right for it to be a pulley, they turn faster. It could be a ticking injector, which isn't bad in itself but obviously not great.

It kinda doings like the belt, but I can't be sure.

How tight are the belts? You can grab one of those belt tension gauges to test them.

Update guys, so i consulted many people, and they say it's the belt's doing ( the car had a full body paintjob recently and spraypaint might stick to the belt and make it dry or something). to test the theory, i splash water to the belt and poof, the sound goes away. FFS, i thought i need another rebuild dang. phew. gonna get the belt changed and look in the pulleys too.

Thank u guys for the help!

That was a good test - adding water. Smart thinking.

really? haha.. i hope i didnt damage anything else by doing so. we often use grease to lubricate belts here in my country due to the ever ending summer, though alot of people say it'll mess up the timing and all. well, whatever works right? hahaa

Good thing there is no timing to mess up, in this case ;)

grease up baby!

that came out wrong.

that also sounded wrong.

Is it me or does this sound a bit sarcastic?

One thing I don't miss on my V6 Accord is the timing belt. Always have that paranoia that it's gonna snap on me one day.

https://pics.me.me/looks-like-its-ti...p-10217844.png

LOL. exactly, that really sounded sarcastic to me too LOL.

dat meme tho, i cant unsee. X_X

FINAL UPDATE.

Problem fixed.

Car went into a full body paint job, apparently the paintshop took off the hood and paint it, thus some of the paint dust stick to the belt making it dry. dab alittle grease to the belts now i cant tell if the engine is idling or dead. it's so dang smooth.

Thank u all for the time and help.

God bless!