Rebuilt engine makes a two-tone whining / whistling noise at idle

ctag

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Howdy :ghey:

It's been a minute, but this summer I rebuilt my first D-series engine for a '99 civic my friend gave me.
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It's back in the car now, and running great! But after reaching temperature for the first time I heard this noise begin, and now it's pretty constant at idle.

Video of it, but the sound is pretty quiet:
https://video.berocs.com/w/sgeE4cPX3AuuQCouG1FNvd

Doesn't go away with clutch, so not a pilot bearing or anything. Also isn't affected by mucking with the air filter and butterfly valve, so likely not whistling at the throttle body. I removed all of the accessory belts (power steering, AC, alternator) and the sound is still there.

Eventually I read that having the timing belt too tight can cause a whine. Bingo, I even recall ignoring the service manual and pressing a little on the idler pulley to tighten the timing belt more when installing it. I must have overtightened. So I went out and ripped the darn engine bay back apart to get a ratchet down next to the idler and loosen it. This time I followed directions: Set TDC, loosened 180 degrees, rotated crank to pull cam 3 teeth past TDC, and tightened to about 30 ft lbs.

Buttoned the engine back up, but the whine is still there. My current thought is that the sound is either damaged water pump pulley or damaged cam journals, but I have no idea.
 

ctag

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This is driving me nuts. I can't tell if its a whine or whistle, its inconsistent sometimes even goes away while idling, the sound level fluctuates, and I can't pin down where it eminates from.

My friend helped me take a pipe and hunt around the engine bay listening to the vibrations. Nothing.

A better video of the sound:
https://video.berocs.com/w/i3yS9ATdV9gtfVKfeEfNzc
 

nd4sped

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I am going to assume you put a new timing belt on when you rebuilt it. I had a similar noise and turns out I installed the timing belt washer/disc (whatever ths f**k its called) that sites directly between the crank gear and engine block. Its a ring that keeps the belt aligned on the crank gear.


This disc is slightly concave and if installed backwards will make a whining/grinding noise as it chews up your timing belt.
 


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ctag

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I am going to assume you put a new timing belt on when you rebuilt it. I had a similar noise and turns out I installed the timing belt washer/disc (whatever ths f**k its called) that sites directly between the crank gear and engine block. Its a ring that keeps the belt aligned on the crank gear.


This disc is slightly concave and if installed backwards will make a whining/grinding noise as it chews up your timing belt.
I appreciate the heck out of your suggestion. As soon as I read it I knew I had to double check :rolf:

Took the upper dust cover off and peered down into the timing area, that washer is correctly installed, with the rim bending away from the timing belt :x Oh well, the search continues!

Edit: No, I didn't replace those parts because I'm a dummy. This donor engine came with a newish timing belt, tensioner, and water pump, so I left all three alone and put them back on. No idea what kind of quality/brand/condition they're in besides looking clean.
 

ctag

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My new hypothesis is that the new crank/rod bearings themselves are making the humming noise... Idk if that's even a thing.
 

nd4sped

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My new hypothesis is that the new crank/rod bearings themselves are making the humming noise... Idk if that's even a thing.
If it was a rod bearing you would hear an unmistakable rod knock. Crank journal bearings, I have spun then a few times and have yet to hear a noticeable noise.
Also make sure you do not overtighten the timing covers as that can cause the cover to rub against the belt. Been there, done that.
 

nd4sped

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Also try removing the ALt, PS and AC belts. If that negates the noise, then replace one belt at a time to see if the noise comes back and you will have isolated your problem to either the belt or one of the connected components. Especially the AC idler pulley. That thing is reliable but after 20 years they tend to fail.
 

ctag

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Thanks for the suggestions.

I wasn't thinking rod knock, but maybe that the new bearings were too big (too small of an oil clearance) and humming or something.

I've done the accessory belts already, no dice there. Just went outside and pressed around on the plastic timing cover while it was idling, no change in the sound.
 

nd4sped

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You can always drop the oil pan, if you see shavings then you know you are on to something.
 

ctag

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I can see some pooled oil when I pull the valve cover off, it looks OK. Just changed the oil after doing the 500 miles-post-rebuild too.

OK, I've now replaced the water pump and timing belt + tension pulley. It wasn't either of those. I was so sure... Now I'm at a loss.

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nd4sped

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.....did you drop the pan?
 

ctag

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.....did you drop the pan?
Got around to it. Everything looks fine to me. Thrust bearings are installed the right direction (grooves facing outwards) and the bearings are wearing in. No sign (to me) that the bearings spun, and I read online that the rod/main bearings could hum, but not the connecting rod ones..

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Also took a look at the valvetrain.

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ctag

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Better pictures. The connecting rod bearings have a little burn near the alignment notch.

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nd4sped

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As long as a finger nail doesn't catch anything slap it back together. As far as someone saying it was normal for bearings to hum, that is an absolute first for me in nearly 20 years.
 

ctag

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As long as a finger nail doesn't catch anything slap it back together. As far as someone saying it was normal for bearings to hum, that is an absolute first for me in nearly 20 years.
Just goes to show that enough Googling will get you any answer haha. OK, thanks for the advice, I put the engine back together. Once it warmed up the noise came right back.

I got some directions from a reddit thread, and so once the engine was running I took the plastic air filter housing off and started poking around on the intake. All of the intake manifold bolts are snug, and starter fluid didn't find any gaps. I disconnected the IACV and the noise was still there. Then I held a folded paper towel over the IACV port. No change. I pulled the PCV valve, no change. Then I disconnected the brake booster and plugged the intake port, no change there either.

At this point I would suspect the valves making the noise against the valve guide... Except there's no change in volume when I open the oil fill cap, which I would expect if they were whining.

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ctag

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Took the throttle body apart and cleaned it. Tried swapping out the IACV but the ebay special I put in was broken (or something, it would rev bounce at idle and thew a CEL), so I put the original back in. Tried a new throttle body gasket, but it didn't seal... Because cheap I guess. Wound up putting the old gasket back on and then replacing the intake manifold to engine gasket. Noise is still there but I'm done for today and the car runs.

The not-fitting new gasket:
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The old gasket went back on. There's a puddle of oil inside the manifold (from PCV?)
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OK, now I'm out of ideas.
 

nd4sped

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I hate to say but seems like you are throwing parts at the problem.

If it was a vacuum issue, you would be able to tell by spraying a mixture of soap water around areas that you would expect vacuum leaks. (All around the manifold or any vacuum lines)

You state that it happens when the engine warms back up. So if you raise the throttle to say 2000 rpm, does the hum get worse or does it go away?

Starting to think perhaps the oil pump but I would imagine that would get worse with increased RPM and I would also expect that hum to present at start up.

What weight oil are you using? Perhaps a heavier weight? Im really starting to go out on a limb now. Not seeing and hearing this in person is difficult.
 

nd4sped

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As for oil in the intake manifold, this is typcial of a stuck PCV. Pull the PCV and shake it, if it rattles its good. If it does not rattle then replace the $4 part.
 

ctag

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I hate to say but seems like you are throwing parts at the problem.
Yep. I get bad about that.

If I raise the RPM to 2000 the whining starts to disappear into the sound of the exhaust. I don't know if it goes away or just gets covered up.

Back when I suspected the rod bearings I mixed some 20w50 oil into the 5w30 to thicken it. The Hum seemed to quiet just a bit, but that could have been the idle speed being different. The oil pump is new-ish, and came off the previous engine.

I'll check the PCV, thanks!

I appreciate the heck out of your help troubleshooting this. It's looking like a family friend could use the car, and I plan to give it to them, so soon it won't be my problem anymore anyway.
 


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