I'm new, so i'm sure this has been brought up before, but what is the "REAL DEAL" about the knocking sound that develops in the 2.7L engines when you first start them up (Cold Start).

My 98 Tacoma started doing it last year. Only about 6-12 knocks on cold mornings, but not every morning. It is very intermitant.

Or basically, what is it?
Is it a crank bearing, rod bearing, "piston slap" (whatever that is), Something in the valve train, Squirrels??????????

I've heard that this is a "fairly" common problem with the 2.7L 3RZFE engines.

Can anyone help!

 

What am I, the lone ranger here!

I see sites on the web where folks talk about it, apparently Toyota knows about, but NOBODY here on this site has ever heard of it?

Interesting

 

it is rod knock. slowly developing. its time for a rebuild.

 

which is your rod bearing

 

I noticed the same thing last fall/winter, and again the last couple weeks as it's cooled down overnight. When the weather starts to turn cold, my 2.7 will make a light tapping noise in the engine compartment, which increases in rapidity with acceleration. It only makes the noise when I'm starting the cold engine in the morning, and it goes away by the time the engine's warmed up a little, about a quarter mile down the street.

You guys agree with loki2043, above?

 

In my truck .....And mine alone i know for a fact it isnt rod knock , its either injector or valve related . I figure that most of 3rz ticks are similar to mine so im guessing yours isnt rod knock either . 80 percent of the research i have read on this issue appears that it is just a minor inconvenience ( im hoping yours and mine falls into this category hehe ) and the other 20 percent say its valves that aren't properly adjusted . In my case i know for certain my valve lash IS adjusted to spec sooo im hoping its injectors going out rather than lifters or some other head issue . Anyway yep i feel your pain man , so in short , go buy some Lucas injector cleaner/upper cylinder lubricant and put about 4 oz in your gas each fill up and this will mask the problem , or at least it did for me . Good luck man )

Brutal
Ps check my thread out , hopefully we'll get this issue figured out soon .https://www.yotatech.com/forums/f123...solved-223791/
Pps You will know if its rod knock , there is no mistaking it , if the sound is coming from the top end ( and it sounds like a light ticking or pecking sound .)then its probably the common 3rz ticking issue i have . =)


( edit ) wow i just noticed how old this thread was hehe dang i must need sleep )

 

IMO, it's just dry valves. This is especially apparent in many other engines. Mostnotably, my motorcycle. The first couple seconds, you hear dry valves, then the oil reaches them and shuts them up. Same stuff with the Tacoma. I also notice an increase in RPMs as my oil starts to make it through. I know the difference between a rod knocking and a valve tapping. That's undoubtedly not a knock... at least, in my case.

The other thing is, if it's a rod knocking, the sound's not going to just go away when oil hits it.

 

That was also my hypothesis, Ricky, but I wanted to hear it from you smarter guys.

 

Old thread but.....

My 1999 4Runner (2.7L 4x4 5spd) started making noise a month or so ago that I though for sure was a bad pulley. I recently had a pulley go out on my '85 4Runner and so I know what they sound like.
So being as it would only make noise for a few seconds or up to 3 minuets after start up and then it would go away until the next morning I went ahead and replaced the two tensioner pulleys (PS & AC) as
I was unsure of the miles on them. Well the next morning still had noise so I did a ton of reading online and hearing different hypothesis of what it was from. It was comforting to hear that lots of others seam to
be plagued by this but the fact that it did not always go after 30 seconds bothered me also i don't like the noise

So I threw some marvel mystery oil (found at walmart or other autoparts stores in a purple/red container) in the engine and in the gas tank around 6-8 oz each.
the last two days have been cold 16*-19* and no noise!

I thought I would share as I'm sure other 3rz owners could benefit from this

3rz 4Runner
282K+ miles (frame trans axles body)
100K miles on engine
5W30 Full Synthetic

Noise started at some point this winter (currently in Wyoming)

I will update if the noise comes back

 

My 2 cents its piston slap. My hondas do it too when cold. Im in ontario and the colder it is, the longer the sound lasts. Cold for me is -20 to -30C, thats like 235F?..??

 

++++Update++++

This morning it was -20*C and no noise
At startup my ultra gauge said the engine temp was 6*F (-14.5*C)

Yesterday evening I had the noise after work it was -9*C engine temp not noted at startup.
Noise continued after idling for a min or two of idling and then continued for a block or two as I went to the local Napa.
I shut the truck off and when I returned to the vehicle a few min later it made the racket for 3-4 more blocks.

Seems inconsistent but if I add a little Marvell Mystery Oil the day before it doesn't seam to make the noise the next day.

 

The reason it only works for a limited time is due to the solvent (white spirits) boiling off

mmo just dilutes your oil (it's roughly equivalent to a 3-5w, 3 when it goes in, and 5 once the solvent boils off) why not just use a 0wXX and let the engine warm up properly!

​​​​​​​The other option is a single weight, but it will be more harsh on the engine at startup and you'll want to preprime the system every time you fire up (disable ignition and fuel, crank crank crank, then you can fire it up)

 

It is very common for Hydraulic Lifters to tick, there may be updated lifters for your motor, ATF would also bandaid fix the issue like mystery oil, or you may have a weak oil pump(easy to test). If it is the lifters there is no damage occurring that will harm your engine its just going to be loud for the first little bit until you replace the lifters or run an oil that will provide better flow, carefull with the lifter replacement as you need to prime and bleed them properly or engine damage can result. I know my 1992 4G63T Eclipse needed updated lifters with larger oiling holes, problem solved nice and quiet now. I wouldn't guess piston slap unless it was raced or over revved, and that can only be determined by a complete tear down..