Not the Typical Topic- Need Advice on Engine Noise

[Horder]

I value all the knowledge and experience on this forum when it comes to my Classic cars so I was hoping to get some help opinions on a driver.

2006 Acura TL 3.2 V6
110000 kms (Canada) 70000 miles

About a year and a half ago this engine starting making noise. It is perfectly quiet upon start up. When in summer it might only stay quiet for 15 seconds. In our cold winter it might stay quiet for over a minute. Then it starts to click. Sounds like once per revolution. Frequency increases with revs. But....if I put my foot on the brake and put the engine under load it goes away.
I would say the noise might be getting a bit worse over this period of time. My mechanic thought it needed a valve adjustment so he set the lash. No better. He said with #5 coil pack off the noise was less. Took it to a well known Acura mechanic... he said it’s piston slap and drive it. He said it will be fine for a long time. I thought piston slap was worse at cold and got better as the engine heated up. Can’t imagine why the noise would diminish under load?

I thought the temperature and load changes to the noise might be significant to diagnosis.

I was thinking rod bearing but could it go this long? Wrist pin?

I’d appreciate any advice..

[fordified]

Could be piston slap but that would assume significant bore wear at 70,000 miles. Unlikely in my view. I would think timing chain. See if you have a timing chain adjuster on the head and or block. I don’t know anything about Acura’s but many OHC engines have them. Most are spring loaded that can get weak over time.

Just a thought.

[chimpvalet]

If it's just a fairly light tick I'd relax. I drive an '05 Nissan which produces what sounds like piston slap after start-up, usually in the summer months oddly enough. Hasn't crossed my mind since last summer though I drive it frequently, and there has been no ticking. 210k km's and well maintained, drive it hard only on blue moons.

[hoodeng]

Piston slap and some bearing noises can be played by varying load on the engine. Valve train noise is not under the same influence, so noises will stay pretty much as they are regardless of load, be it constant, variable, rpm related, cold only, hot only etc.

[mag2555]

This may sound nuts, but I think you need to try this to further narrow down what’s going on.
the part of your comment where you mention that under a load with the brakes on is a big clue and odd also.

Set this test up .
Find a way to put the motor under load. But without the brakes being applied.

Maybe be means of a tow rope or chain restrainting the car from the rear bumper.
If in making a test like this the noise is gone then maybe it’s related to the brakes being on and might be caused by something like very worn PCV ball rattling around with vacuum fluctuations.

[Racer71]

There was an updated valve adjustment clearance on those J series engines as well. It’s supposed purpose was to help with spark plug oil fouling, it’s been few years since I’ve done one, it was for the exhaust valves only iirc.

[allencr267]

Exhaust leak. Some close up when hot.
Use a stethoscope, coupla feet of your neighbor's garden hose, locate where it's coming from, don't get tangled in the belt/s.
Good luck.

[dannobee]

Are you sure it's not a timing belt tensioner? Put a stethoscope down by the rear bank on the exposed part of the tensioner and see if it's loudest there.

[mitch]

It could also have a cracked flywheel

[rebelrouser]

It could also have a cracked flywheel

Never seen an import crack a flywheel, but yes it will make a noise as described, also torque converter nuts loose, which I have seen on import cars will make a noise as well. Seen several engines pulled because of cracked flywheels, though they had bearing or piston problems.