Cold start engine knock 4.7

[Tundrarodney]

I've noticed a pronounced engine knock whenever I fire up the engine on my 2000 4.7 limited AC. This only happens in temperatures below 25 to 30 degrees and lasts for about a minute. Sounds like a rod bearing or wrist pin slap, don't like the sound at all !! I've got 130,000 miles on the odometer and have always run on 5w-30 full synthetic. The oil pressure is great and the engine doesn't loose a drop between 5000 mile changes. Anybody out there experience the same problem, and, should I worry about it ??
Thanks in advance for any feed back.
Rod.

[DeebsTundra]

I don't know if anybody else feels the same way, but almost every Toyota I've ever heard fire-up in the cold sounds that way.

My Yamaha does it too.

Does it continue loudly even after warming up or does it smooth out as it warms up?

[rando]

What you are hearing is most likely rocking of the piston skirts. As the crank goes over top center the piston rocks from one side of the cylinder to the other due to the change in direction of the force from the connecting rod.

At cold temperatures, the pistons are small and skirt clearance is higher. Being aluminum, they shrink more than the cylinder bore when they get cold. As they warm up, they grow fit the cylinder and the noise goes away. My Honda VTR1000 had a similar noise on cold startups.

Pretty typical.

[H2O_MAN]

Yeah, it's typical in the cold.
Once the engine warms up the knock is replaced by the ticking injectors - it's all music to my ears

[craneman]

It was -18C this morning when I started up and no different noises from my engine. The starter had to grunt a little harder but that's about it.

[Barren]

When I haven't started my Tundra for a few days and its cold(like this morning) it makes funny noises when I start it. Only last for about 1-3 seconds then its gone.

[devo]

I have ~87k on my Tundra now and have been noticing the sound too.
I'm almost positive it is the valves. Sound goes away once oil pumps up. I imagine you are hearing the same thing if it goes away quickly (within a minute). If that is the case, I wouldnt worry about it. If the noise gets louder and is a clear "knock" that is another story....very doubtful that is the case on this engine.

[Gunter]

Everytime I seem to start it, the revs are at about 1.4-1.6k, it makes a high-pitched whining sound, then goes away after about a minute, and about 4-5 minutes later the engine will drop to about 800rpm.

Other than that, nothing odd on mine.

4.7L 2WD Auto DC '05 w/ ~6400mi