4m40t knocking top end

[Pickles77]

Hi all,

As title says, 4m40t knocking throughout all rev range. The noise appears (after lots of investigation) to be coming from the top end. Not as violent as rod knock, and there was no play when the motor was apart.

So far:
-Pulled head to check for any piston on valve action, there was no sign of any odd wear
-new head gasket (correct one)
-cleaned and reassembled
-Re-shimmed valves (some intakes were 0 or negative)
-Rebuilt injectors
-No loose valve train items visible
-Timing cannot be even one tooth off or valves hit pistons, which I checked
-Isolating cylinders by cracking injectors doesn't affect knocking (plus all cylinders firing with good compression)

One thing I noticed last night, was that when the tensioner was losing oil and not holding pressure, the knock went away. So today, I will replace the tensioner and come back with further info. The only thing that looks like it may contribute is the guide that the tensioner actuates, if the tensioner is failing, it may be hitting the case. Tensioner looked fine all the times I had it out, however it did not hold much tension when I had to reset for reinstall. Will compare to new one shortly

New tensioner felt a lot different and held tension better, knock was gone on first start after this but shortly re-appeared. Next step is the guides and chain, whilst checking all gears for damage. Without oil pressure into the tensioner, the noise is absent? Any ideas?

Any more ideas will be greatly appreciated. I have scoured the internet and cannot find anything the same as what I am experiencing.
The noise sounds very similar to the start of this video; https://youtu.be/s1bL2McGa0Q

[Pickles77]

Went for a drive, car drives great apart from the knocking.
Heat in the engine made zero difference to the noise presence or amplitude.

Not sure if related, but she is currently rolling absolute coal. Anti-tamper locks are in place and appear to be so. Thinking issues related someway.

[Pickles77]

Hi all,

No updates yet, have uploaded a clip to YouTube to hopefully help find a diagnosis.

https://www.youtube.com/watch?v=uRJJN4drIhc

Kyle

[TimTams]

• cracked injectors to rule out wrong timing of injector pump
• valve clearances OK
• engine timing / chain / tensioner checked

How were the bores looking when you had the head off?

Not much left to do but check the bottom end. Could also be a gudgeon pin

[starjunk]

Can you further isolate location by using a large screwdriver as a stethoscope? (blade against different parts of the engine, handle pressed to your ear)
Comments on your Youtube vid seem to indicate that the knock speed is half that of the engine revs. Can you confirm this?
Another thought - injectors can get noisy, and this you could pinpoint with the above stethoscope idea.
Finally, the tensioner comment interests me.... If I misread your post on Youtube, and the knock sound is once per revolution, then it is theoretically possible that the timing chain itself has a defect that causes the sound every time it comes around to the tensioner.....
keep us updated.

[Pickles77]

Hi guys,

Thanks so much for the replies.
From past experience I am under the impression gudgeons would be double tapping, faster than half engine speed? I am fine to stand corrected as I just want an answer to this. This noise really doesn't sound like any bottom end noise I have ever heard. Cylinder bores looking perfect for 180kms.

Screwdriver seems to sound like its coming from head definitely, and towards the front either around first cyl or timing chain area. All the chain, guides and tensioner are new, so I don't believe it is this.
Injectors are all new, cracking injectors doesn't get rid of the nosei completely, but it does seem to be slightly quieter with first cyl cracked. May be not as clear as the motor is noisier running on three cylinders. I have an actual mechanics stethoscope coming in the mail, so hopefully it can shed some light.

Definitely half engine speed, the knocking is hard to capture on video as it is only audible in person in certain positions the to motor. From some angles the motor sounds awesome.
I think the tensioner oil pressure issue may have been a fluke as I cannot replicate this again unfortunately.

Has anyone had/heard of any of the valve train failing that may cause this issue. 1st cylinder seems to have at least twice the carbon buildup to the other ports, will clear this out in the hope carbon buildup is lining the valve seats.

[TimTams]

Just to clarify, what does this mean?

she is currently rolling absolute coal. Anti-tamper locks are in place and appear to be so. Thinking issues related someway.

At this point the issue sounds serious enough to warrant taking the head off and having a look.

[Pickles77]

Under heavy load a lot of black smoke, the anti-tamper cover on the fuel adjust is still in place.

The head has just been off with no signs of damage anywhere lol

[TimTams]

Under heavy load a lot of black smoke, the anti-tamper cover on the fuel adjust is still in place.

The head has just been off with no signs of damage anywhere lol

Ah you did say the head was off. Tough one, im out of ideas... I keep coming back to things youve checked. Precombustion chambers looked OK? Couldn't be a broken piston ring or youd see that on the bores... Could be something up with a cam bearing maybe, might be worth taking the caps off one at a time to inspect but i cant really see that producing a knock

[Pickles77]

I just got my endoscope, so I'll check out the inside of the pre-combustion chambers when I have a free few hours. The bottom side of the chambers were all good, no cracks or damage.

Will report with findings from borescope and some photos as well if anything interesting.

[TimTams]

Not sure if related, but she is currently rolling absolute coal

Haha just discovered this is an actual phrase



Love it

[Pickles77]

Hahahaha yeah it's a funny one lol.

Alright no information gained from endoscope. I am sure the issue is fuel related, I have been driving the car around to try and make something break so I can fix it. lol.
Lower RPM [1500-2500] and under heavy load, the car is overfuelling a lot and increases the rattling/knocking whilst spitting a LOT of smoke. Now I need to work out what and how is causing this.

Workshop manual is of no help here.
Looking from the rear of the fuel pump my lines are connected as:
1 2
3 4
This is the right firing order but everywhere else I can find any information regarding this has them all moved a position clockwise. Can anyone confirm this order. I have assumed this is correct but now I am doubting it. Would explain why knocking doesn't go away whilst cracking injectors, because it's more than one cyl.
I have spoken to A1 injection and he isn't aware of an common problems here. I am planning on taking the car down there for him to take a look this week.

Is there a error code logging system on these vehicles? My scanner will not recognize the car and there is no CEL to ground the plug out like I have done with the 6g72.

[Pickles77]

Overfuelling gone, blocked EGR completely and bypassed coolant through fuel pump.
Valves little gunky from EGR blasted some water and solvent through intake but no difference to knock.
Strong oil flush and valve noise additive, no change.
Confirmed cylinder 1 is the culprit. Loudest point that I can hear knock with stethoscope is on the intake manifold above first cylinder. Noise is barely heard around block and rest of engine.

Currently have two hypothesis.
- Worn gudgeon pin, doesn't sound like like this from experience but I'm at a loss.
- Uneven valve seat, hearing either valve rattling or spring hat being pushed into bottom of cam.

Currently driving car until it breaks something, then I have something to fix.

[Pickles77]

Hi all,

It was a slapping piston. Spewing that I missed it when first pulled motor.
All fixed and sounds and runs great, piston was rooted, somehow did 0 damage to bore. Still had cross-hatching the whole way down which is probably why I ruled it out in the first place.

Kyle