Fresh Rebuild Knocking from back of Right Cylinder Head

[DevenReilly]

https://www.youtube.com/shorts/gaUeBxouF2g

Just rebuilt the whole motor. Lifter tick, timing chain, or something else?

[ShelbyM3]

Is this initial startup or have you put miles on it yet?

It could be a chain tensioner needing to establish a solid pressure. I know when I fired up my 2.7 build there was a tick from the valve train, which is pretty normal, but after some heat and revs it smoothed out.


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[DevenReilly]

Its on jack stands right now. Has idled for about an hour at this point. Noise seems to get worse when its warm.

[ShelbyM3]

Engine sounds good to me, I almost wonder if you’ve got an exhaust leak on Bank One at the manifold to downpipe, right back there. As it warms up the leak may get a little more pronounced.

Did you replace all the gaskets and torque them to twenty five Nm?


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[Rol-co]

The tapping sounds like the intake manifold flapper, the tensioner sounds faster like mine did.

https://youtube.com/shorts/9fq3c3y2w...UpMn4jR6pXLR1U

Faulty new tensioner


Edit:
Did you operate the lever by hand already?

[DevenReilly]

After the install I forgot to install the coolant pump driveshaft. The engine never overheated and I quickly diagnosed the issue, installed the shaft, and started it back up. There were terrible popping noises from the back of the engine as the after-run pump kicked on after engine shutdown (Not the same as the video). I am wondering if I overheated a head due to lack of coolant circulation and those noises were coolant rapidly quenching an air pocket, cracking the head, and introducing the noise in the video. There is a not-insignificant mount of smoke from the exhaust but it has been cold here in NY for the past couple weeks, it dissipates quickly and doesn't smell like coolant but it is enough to make me concerned. It smells like the engine is running very rich. There's no milkshake on the dipstick but it hasn't been running for long enough to create that condition. I'm going to run a leak-down and compression test on each cylinder and report back.

[DevenReilly]

The tapping sounds like the intake manifold flapper, the tensioner sounds faster like mine did.

https://youtube.com/shorts/9fq3c3y2w...UpMn4jR6pXLR1U

Faulty new tensioner


Edit:
Did you operate the lever by hand already?

I did operate the flapper manifold by hand, it was making a different noise that would go away when it was manually actuated. This knocking noise is persistent and different.

[Rol-co]

I did operate the flapper manifold by hand, it was making a different noise that would go away when it was manually actuated. This knocking noise is persistent and different.

Okay,
And did you tested the tensioners before mount, I personally never put one in without testing, just pop out the piston and spring, put the piston back in and air test it.
Don't thing the heat has done something but you never know without flow and just filled up.

[DevenReilly]

I did not test any of the tensioners before install, just slapped them in.

[emilio]

pick up an engine stethoscope for a fairly easy and inexpensive way to locate the sound, or at least eliminate possibilities. they're $15-30 and come with a thin probe you press against suspected areas.



from the top of the engine you should be able to sound out the cams & lifters, cam adjusters, and cam chain tensioners. depending on the probe length, crawling under the car might give you access to the DPs and the sides of the timing cover just above the transmission's bell housing (might need to remove the axle shields, can't exactly remember how they go). listening to the left and right sides of the timing cover should isolate the timing adjusters from the cams.

[DevenReilly]

I pulled the engine. Ran a cold leakdown test (really should have done this with the engine in so it could be up to temp). All cylinders have perfect leakdown results. There are no visible issues with the head. Cylinder bore scope shows what appears to be dew on top of some of the pistons. The tensioner on the back of the right head can be compressed easily by hand, whereas the one on the back of the left head where there was no noise, takes significantly more force to compress.

[87vr6]

Welp, sounds like you found the noise, chain slap due to a bad tensioner

[DevenReilly]

Welp, sounds like you found the noise, chain slap due to a bad tensioner

Is there a recommended way to test them besides just finger-fucking them?

[DevenReilly]

https://youtube.com/shorts/Xth3gh03ydQ?feature=share

[Rol-co]

Like this

https://youtube.com/shorts/GtLbJeb0z...mcPkSBORhQME8V

My (defect)new one
https://youtube.com/shorts/bhsQHUOvq...dpOLew0aLfqGVr

[DevenReilly]

Like this

https://youtube.com/shorts/GtLbJeb0z...mcPkSBORhQME8V

My (defect)new one
https://youtube.com/shorts/bhsQHUOvq...dpOLew0aLfqGVr

How many PSI are you testing these with?

[DevenReilly]

Pulled the right head off. No deflection on the head or the block - tested with a straight edge. My smallest feeler gauge couldn't even fit under. Haven't ruled out a cracked head yet, bringing them down to be pressure tested tomorrow.

[Rol-co]

How many PSI are you testing these with?

The one who was not working at 87 psi
The one who was leaving me at not even 20 psi

The oil hole was blocked, no air coming trough.

[q_dubz]

go drive the car, put it under actual load. then report back.

[DevenReilly]

The one who was not working at 87 psi
The one who was leaving me at not even 20 psi

The oil hole was blocked, no air coming trough.

Interesting. Where'd you get that failed tensioner? Was it OE? I bought mine from ECS Tuning by a brand called Bremmen. I am replacing it with an OE one.

[Rol-co]

Interesting. Where'd you get that failed tensioner? Was it OE? I bought mine from ECS Tuning by a brand called Bremmen. I am replacing it with an OE one.

Audi dealership, oem part, had to buy a new one, audi warranty is: "bring in the car and we'll look if it's properly mounted"
Impossible to do without suspension.


Be aware for china versions, whole set of chains tensioners and guides not even 300 usd, that can't be good.

[DevenReilly]

Spoke with Alex from AMTuned. His opinion was that it could be the hydraulic tappets. They were all seized. Pulled all 40 of them, freed them up in the vice at his recommendation, soaked in gasoline overnight then in motor oil for another couple hours then reinstalled. I also ordered OEM tensioners, I do not trust the off brand ones that were on there. At least these have an Audi logo on them. Reinstalled the heads yesterday, working on the cam timing today.

[DevenReilly]

Reinstalled the engine with the freed up tappets and OEM tensioners, runs like a dream. No more noises.

[Rol-co]

Reinstalled the engine with the freed up tappets and OEM tensioners, runs like a dream. No more noises.

Glad it worked out for you! I personally think it was one off the tensioners, if there is a tappet stuck the valve didn't close, if its broken the tapped don't start to work after freeing up.

[q_dubz]

good to hear!