cnmrosko

Hi,

Maybe someone here has had a similar problem and can shed some insight here.

I've got a 4runner Limited V6 3.4L, with 218,000 mi. I started noticing a knocking sound about a week ago that seems to be coming form the passenger side of the engine and seems to be in the middle or lower portion of the engine. The knock is noticeable at operating temp at idle and less noticeable at higher rpm and when under way. (This may partially be due to increased road noise.) The knock is not noticeable when engine is cold. The knock seems a little louder when at operating temp and in neutral or when the engine is NOT under load. If I put it into drive and step on the gas and the break at the same time to create a load the knock is less loud but still there. I've had the 4runner since 125,000 mi. and always run it with mobile1 change oil 2 times a year.

Thanks,
Chris

tns1

I saw that someone else was able to record high quality audio of his engine knocking to a file which he then posted. If you have a laptop with a mic, or a camera, or a fancy cell phone, maybe you could do the same. Is the knock random at all or very steady? High pitch or low? Sharp or dull? Does the rate follow engine RPM or is it somewhat unrelated? Can you hear it better from underneath?

My own 98 ltd, 200k mi, has a random knocking which seems to be in the tranny. I only pinpointed this by getting under the car. Not saying yours is the same, as there are many things that can cause knocking - basically anything that rotates.

Montana_Tom

I had a similar issue, sounded like a knock from the engine, but my local dealer told me that it was from the transmission as well and that it was fairly common. I have a 96 T100 with the 3.4L automatic 4x4.

Evilmunkey

I agree more w/ Trans knock, due to the motor will knock more while cold than in operating temp, especially once under operating temp is when most people notice sounds that occur w/ their Trans. .

Montana_Tom

Interesting find... I had to put a new automatic transmission / transfer case in my pickup, picked it up today from the shop, and wah lah... no more noises!

ntoracn

I'm currently dealing with the same exact problem. Looki at my posts under my sig for more details. The root cause of my problem was 2 hurt pistons when the previous owner overheated the motor. They had a Toyota dealer install 2 new heads but didn't know the bottom end was hurt. They decided to sell the vehicle since they had already invested $2,500 in the new heads and now the dealer was telling them they needed to spend another $4,000 to solve the problem. Now your problem probably is something else, there are known noises from the fuel evap system and valve lash that can cause excessive engine noise. Did yours ever overheat?

ntoracn

I think is a link to the video of my you tube video of my engine noise. Good luck.

http://www.youtube.com/v/mVQtguJvbsQ...dded&version=3

Texas_Ace

That is not a good sound.

First thing i would do is get a mechanics stethoscope and then try to figure out where it is coming from.

When you pulled the oil pan did you pull and rod/map caps? Ideally you would pull them all to see if any have signs of wear, just do it one at a time and put them back the same way they came off with a torque wrench and you would be fine if there is nothing wrong.

Usually you won't feel a loose rod unless you full on spin a bearing.

ntoracn

Thanks for the reply. I ended up pulling the motor back in Janurary, 5 days before my serious motorcycle accident and found two scuffed pistons causing the noise. The thing that kept throwing me off was the noise going away under ANY load. The previous owner had overheated the engine and had the heads and gaskets replaced not knowing that the pistons were scuffed during the overheat. The motor ran smooth without any smoke or missfires, compression was at the low end of spec, but even across all cylinders, power was good.

Texas_Ace

So some of the pistons were replaced? Was the engine bored out when this was done? Were clearances checked? It could be piston slap, that can act like this.

ntoracn

As I understand it, the previous owner overheathed the original engine and the Toyota dealer wanted to replace the whole engine for $5K and get a 1 year warranty or replace the heads only for $2.5K but no warranty on the bottom end. The customer picked to do the heads only and it bit them in the butt. Since I bought the rig, I've only taken the motor apart. I will probably just install a good used engine to get it back on the road and keep the new heads as spares and junk the rest. So no new pistons or boring

Texas_Ace

That is the best idea, i usually just replace or do a full rebuild in situation like this.

Reilep

I have a 97 t100 with 270k. That sounds, sound the same as mine and it was a cracked flex plate. It is what connects your crank to your torque converter. It is not heard at first but when it warms up it sounds more peodominent. Have to pull the trans to get to it. I did mine and it is running goid but i do for sure have valve noise. Hard to know what to do. Good luck.

Firebugs73

I have a 1996 Tacoma 3.4L v6 that in 2013 cracked both heads with about 300k miles on it. Swaped heads and has ran great till now. Now 2017, it wouldnt turn over the other day, batt was good so I pulled plugs and found #6 full of coolent. With plugs out, spun it to blow them all out and it ran fine and sounded great. Then CEL lite up, had it checked to learn #6 misfiring. Took Lt head off and had it checked/ pass all test with no cracks. Put new gaskets on going back up, new water pump, timing belt, tention and all was replaced. when I got it together and fired it up, if sounded very bad but it runs great. Knocking fast and up with more idel. Tore apart many times to recheck everything and marks on cams are all lined up. TDC, cam marks at 12 even. Still sound the same. I am at the end of my rope. I have heard its jumped timing but how would it run great if so and how it jump if all marks still line up as they should?? Any one able to point me in right direction for help please?? Thanks Trying to add vid so your able to hear it also.

Firebugs73

aowRS

^ That's bizarre. At idle it sounds like a Cummins 4BT...




Andreas

Firebugs73

Maybe I can sell it as a Toyota diesel, just minus the power of a diesel lol. Even after a head and cam swap it sounds the same. So if it is in the lower block, I just as well swap motors since yea gotta pull motor to even check lower part due to 4x4. Unless someone has or knows something I am missing??

Lele1990

So I bought a 96 4runner in March from my little uncle, lol who is a great mechanic. and rebuilt the motor in the 4runner about 2yrs ago, he says. Well last Tuesday I'm driving down the hwy.. a loud knocking noise comes from my engine, outta nowhere. Oil light came on & went right BK off. So I pulled off on to the exit got oil, a guy at the pump checked it for me, I was good on oil. It wasn't running hot, or anything. Well I proceed to my 20 miles drive home. The knocking fading in and out or getting louder at times, I think! Well about five minutes before I get home it shuts off, I turn the key over crank it back up and drive home. Where it's been parked since. A few ppl Sid different things it coul, be. I have no clue. Just really hoping not the motor.

ME63

What was the cause? Mine is doing the same.