Strange noise Tacoma Prerunner

First off I would like to say hi! I recently(3 months ago) purchased a 2001 Tacoma PreRunner after wanting one for so long for a daily driver. Well all has been well I changed the oil for the first time (used Mobil 1 and Mobil 1 filter) then changed fuel filter, trans fluid and rear end fluid then spark plugs. Pretty much changed everything so I knew everything was fresh. Well here recently I've been noticing on warm start up after sitting for 10-15 mins the truck seems to knock not a loud knock but you can hear it from under neath the truck. I'm really not too sure what it is or where to start. It doesn't make this sound on cold start up and if you rev the truck after warm start up while its making this sound the sound goes away. Then comes back as the idle drops back down and then goes away around 60 seconds of the truck running. Its a 2.7l and only has 120k on it. Any ideas or thoughts? I have googled this and can't find anyone with this problem.

 

So ... it did NOT make the sound BEFORE you changed fluids?

 

No it did not. I even changed the oil back to what the other owner had in it. However I did not know what kind.
Of filter it had on it before so that's why I put the Mobil 1 on it

 

Are you using full synthetic oil?

 

Next, I would try an OEM oil filter from the dealer. I believe they have an anti-drainback valve that many aftermarket filters do not.

I never use anything but OEM oil filters on my Toyotas.

 

Yes I'm using Mobil 1 full synthetic is that bad? And Rick thank you I did not know that I will go first thing in the morning to Toyota and get a oil filter and switch them out. The filter could cause this slight knock on warm start up?

 

I switched to Toyota oil filter and it still makes the sound upon warm start up

 

It coul be the synthetic oil could be to thin might wana try regular oil

 

Is there an oil that you reccomend?

 

Try non synthetic or a little bit thicker viscosity synthetic oil.
Hopefully some else with a 2.7 might now

 

I went to Walmart changed the oil to regular Castro GTX conventional oil and the sound is completely gone on warm start up. I guess the synthetic was breaking down when warm. Thank you!

 

After driving the truck to work and letting it sit for 15 mins I went out and started it again to make sure the noise is gone. Well its back now same knocking noise as before I have no clue what it could be

 

Do u know exactly where the knockn noise is coming frm? is towards the rear engine,

 

Somewhat, as much as I hate to say it it almost sounds like its coming from the oil pan

 

Did u buy from a dealer or private party? What did the old oil look like when you first changed it? The knock could have been there previously but the previous owner could have covered it up by using gear oil mixed with regular motor oil, or any other form of masking a small engine knock. Sometimes just using ad additive like Lucas can cover up a knocking sound.

 

I bought from a private party. The guy always took the truck to this place to get the oil changed beside his work. He even had all the reciepts for it. Pennzoil oil was always used. It was.changed maybe 1500 miles before I bought the truck and the oil looked brand new when I drained it

 

Well that's a good sign then!

 

What's the popcorn for? Lol

 

Haha I'm just interested in what the out come of this is.