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Engine Knock

I am driving a 2001 Toyota Tacoma. When I have a cold start, I get knocking like metal on metal in the engine. It doesn’t happen all the time, maybe thee out of five cold starts. After about 30 seconds of driving time, it goes away. This also only happens in the winter. Any ideas?

Are you using the proper winter-weight oil per the manual?

Could be piston slap, but that would likely happen all the time, not just in warm weather. Is you Tacoma equipped with the V6? Some Toyota V6’s had a sludge buildup problem, but if yours has lasted this long it’s probably not effected.

How many miles does the truck have on it?
Has it sustained any overheating events?
Any low oil pressure events?
How’s the maintenance been?
Which engine?
Have you checked anything so far?
Are you the original owner?

The first thing’s I’d suspect are possible bearing knock or a collapsing hydraulic lifter, the second being possibly a result of sludging. My questions are to try to suggest which is more likely.

I’m unaware of any Toyota engines with a piston slap problem, so I’d be inclined to consider that a low possibility. GM has had that problem.

Truck has 77,000
No overheating…runs great after warming up.
Still getting 20-21 mpg
No low oil
I change oil every 4 months (only drive about 6,000 miles per year)
Four cylinder engine (big one for the prerunner)
Haven’t had anything checked yet.
Bought the truck in 04 with 45,000

Some one else had suggested piston slap, but I was unable to find any info on that topic with Toyota.

yes 5w-30 as per the manual. Driving in tidewater VA, so it is not too cold

Sounds like hydraulic lifters that are taking just a short time to pump up and do their job…this may just be one bad lifter, but if it stops fairly quickly, it is not worth determining which and replacing…No cam wear is likely unless you are really hearing a loud noise that is continuous…I remember when cars had solid lifters and start up noise was normal until heat expanded parts etc…worry about something else…

Also agree with hydraulic lifter as the source of noise. Usually this more of a “tapping” sound and not a knock. A knock to me is louder and deeper in the engine, so if it is really a knock you may have a bearing going out.

To keep things from getting any worse keep changing the oil. You are not driving a lot of miles. This means frequent short trips that do not allow your oil to warm up and burn off water that condenses into the oil on these frequent short trips. A synthetic oil is a better choice for you. It lubes better and sticks to the metal better reducing friction on wear upon start up.

In some cases I have seen additives actually work for this type of problem…try using a can or two of CD2 Detergent additive or equivalent other brand…make sure it is a detergent additive. If they work it will usually be within 1000 miles or so. Again this is mostly an irritant, but going to sythetic and occasionally getting this motor and parts well lubricated is a good set of ideas too.

Change out your oil filter, making sure you use the right one. Check back and tell us how it worked and tell us if you last had your oil change done by a quick change place.

There are quite a lot of discussions regarding Toyota engine piston slap on the net. Google it, see if those discussions help.

piston slap usually starts on an engine that is fairly hot and not just as start up. While similar in sound the conditions of origin are vastly different.

Could be. The Toyota write ups I’ve seen all relate to it as a cold start issue that goes away with warm-up. Just a possibility.

had similar problems with my Avalon that I bought new during first model year. They had problems with wrist pins and the short skirt pistons used in this engine. Piston slap (at least the little bit of ticking isn’t hurting anything, but I expected a quieter vehicle)