Rod knock in my motor? Need any advice I can get!

[SHOBrad]

OK, so don't flame me but the car is question is a 2016 Veloster n/a that supposedly just had a burnt valve. I let my 16yr-old son talk me into buying and fixing it because I thought it'd be a good opportunity to spend time with him getting our hands dirty and maybe passing on some knowledge. In a past life I used to build and drag race small block Fords. I've been on a 4.0 Jeep kick lately.

So first off we pulled the head, replaced the bad valve and cleaned up all the rest. New timing chain, tensioner, guides, valve seals, and gaskets then put it back together. Checked lash on all and found the new one to be too tight. Bought a new, thinner spec bucket (this is how you adjust Hyundai engines) for the new valve and all seems right.

Car then had a very specific tick or knock that is exactly 1/2 the rate of the RPM. Took it Hyundai and they said bad rod bearings and it had too many miles to warranty.

Pulled the motor and replaced the rod bearings with Clevite, standard size. No improvement.

Took a chance and bought a lower mileage (1/2 the mileage of ours) core that supposedly only had a bad valve itself. Pulled it and no bad valve but a spun bearing. Cam journals were rough too. (ugh) Pulled it apart anyway and the cylinders looked great and the piston movement in the bore was much less than mine. Maybe ours had piston rock? Pressed the newer engines pistons onto my old rods, used the new block with my old crank (and yes I kept EVERYTHING in order and the right direction) and reassembled. Plasti-gaged the mains and rods and all came in within Hyundai tolerances.

So now... No better. Exactly the freaking same knocking sound.

Next we pressure-cleaned the injectors off of the other motor and swapped them onto ours. While we had them off we pulled the plugs and slow-mo video'd the intake valves to see if maybe one was sticking and the piston as tapping it back up but no dice. I wish we could do this to the exhaust since the one we swapped and re-lashed was back there. Regardless no improvement.

Next we tried the trick where you use a long extension on the piston, rotate the engine just past TDC on each cylinder, push down on the extension and listen for a noise. Absolutely nothing. Ugh.

I have watched several videos of cars with rod knock and there knock temp seems to match RPM. Mine is DISTINCTLY ½ of RPM... cam speed. WTF!!!

I am completely at a loss. Again here are the symptoms:
Knock is EXACLY 1/2 the rate of the RPM. Idle is ~660 RPM and tick is 330 BPM (using a beat measure app on his phone)
Extremely pronounced and noticeable at idle.
Knock follows RPM up when you push the gas but quiets as RPM's drop then comes back as it settles back to idle.
My mechanics stethoscope has it the loudest in the middle of the block. Not the valve cover, fuel pump or accessories. Not the oil pan area.

Being that its 1/2 the rate of the RPM these are my thoughts on where it could be coming from:
Valve-train related.
Between the exhaust/intake stroke where the rod bearing goes from compression to tension
Between the intake/compression stroke where the rod bearing goes from tension to compression.
WFT?!?!??!?

Please, any advice would be appreciated!! Also, if this is the wrong forum please let me know. Getting crickets from the Veloster or Hyundai-specific forums.

Thanks in advance!
Brad

[mt-engines]

Get a stethoscope.

It could be something as easy as a cracked exhaust manifold.

Could also be a sloppy tensioner.

Verify oil pressure..

Could be anything, but its impossible to diagnose over a text based forum

[leahymtsps]

Get a stethoscope.
(My mechanics stethoscope has it the loudest in the middle of the block. Not the valve cover, fuel pump or accessories. Not the oil pan area)

It could be something as easy as a cracked exhaust manifold.


Could also be a sloppy tensioner.
(New timing chain, tensioner, guides, valve seals,)

Verify oil pressure..

Could be anything, but its impossible to diagnose over a text based forum

[BillK]

When you replaced the timing chain did your replace all of the sprockets and the cam phasers ? I do a bunch of heads for the local Kia dealer (same engines) and the phasers are almost always worn badly. Also I know of two shops that got burned by using the cheap "white box" timing chain sets. I would use either oem or Cloyes.

The only other thing I can think of is a piston pin making noise. They can sound like a rod bearing.

[SHOBrad]

Thanks guys, I did use a stethoscope and the sound was coming from mid block, about where I would expect a rod knock to occur. I would say it was slightly louder toward the tranny too.

I'm ashamed to say I bought a timing chain kit off of Amazon. It was a "NewYall" brand. I'll keep that in mind.

I did not replace the cam phasers but I tried both sets off my motor and the motor I bought. No change at all. I thought about wiring the phaser valves to power individually while it was idling to advance the phasers and guarantee that the slop was out out. It would cause the engine to run bad but if the tick stopped it might be a lead. May not be enough oil pressure at idle to do this but maybe I could cheat with compressed air... at least on the exhaust cam.

When I replaced the block and pistons I pressed the bad rods off and my rods on. The pins all felt good. Like I mentioned there was a little piston slop with this block/pistons but not as bad as the original. Regardless no change in sound at all from one to the other.

Keep it coming guys, this is the kind-of thought I need!!! THANKS!!

[BillK]

When I replaced the block and pistons I pressed the bad rods off and my rods on.

Do you have a fixture to do that without distorting the pistons ??? Did you press the pistons back on or use a rod heater so there would be no stress on the piston ? 99% of modern engines have pistons that are virtually impossible to press apart without hurting the piston. I will almost bet that if you measure the pistons they will be distorted and there is a good chance that is your noise

[Dan Timberlake]

Once upon a time a buddy got his passenger Chevy V8 rod and pistons assembled by a highly respected machine shop.

He took the engine down at least twice looking for slight knock.

Turned out the shop did not understand the factory piston forward /back marking notches, and put 4 of the pistons on backwards.

He was hearing piston slap from the reversed piston offset on 4 pistons.

[Racer71]

Doing a 2.4 Kia engine now, common spun #3. Other three rods checked ok, crank was cracked. Interestingly, Kia doesn’t recommend heating the rods, just cold press, which was surprising. We heated anyhow. Have you rechecked lash on all the valves?

[1980RS]

Here is something I'll toss out that I saw on a YouTube video. There is a little roller lifter under the mechanical boost a pump that the lifter fails and sounds like a rod knock. Worth taking a look at, just do a search for it. Guy was working on a 2011 Sonata but yours might be the same.

[Racer71]

Yes, high pressure fuel pump follower, similar to the 2.0 Vw ones, would be worth a check. I have a 16 sorento core on the floor at shop that was just starting to get noisy, replaced with a used one. I’m currently assembling a 13 sportage one that got new crank etc. if you need any parts from the 16 engine if they’ll interchange let me know.