v0lume4

Hello fine folks,

I have a '98 4Runner Limited with the 3.4L V6. It has low mileage -- just 63,000 miles. I've noticed a ticking/knocking/rattling sound that corresponds directly with the engine RPMs. I am not sure if the sound is coming from the engine (say, valve lash or something) or from something else entirely. I took a video of the issue and have it linked at the bottom of this post that way I can better show you what I'm asking about.

The sound is most noticeable right at the catalytic converter -- I am not sure if the noise is coming FROM the cat, or if the noise is the most prevalent in that area since it isn't far back on the exhaust. I don't hear the sound much while standing at the front of the car. Perhaps it's because of all the other engine noise (fans, etc.). I hear the noise if I stick my head into the engine bay near the back of the engine, though it is most noticeable on the passenger side (again, I'd be closer to the cat at that position). I can hear the sound inside the engine cabin, and it sounds as if the tapping is coming from in front of me (the engine bay), however I cannot confirm that is where it's coming from.

Can you guys and gals help me out? I'm not familiar with these Toyota engines. Have you heard this sound before? Is this the standard noise expected with these 3.4L engines, or do I have something to be concerned about?


Thank you very much for your help. I really appreciate it.



Side note:
I have had some recent maintenance done on the vehicle -- I have not had the truck more than three weeks, so I cannot say whether or not the sound existed prior to that maintenance. I simply don't know. That said, I had the timing belt, water pump, radiator, valve cover gaskets, and spark plugs/wires replaced. I can confirm that the sound existed prior to the spark plug and valve cover gasket repairs.

Malcolm99

Sounds normal to me, but I have seen aftermarket cat's break the internals causing rattling under load or certain revs, also the heat shields on OEM cats tend to loosen there grip on the cat after 20 years causing unnecessary noise..

Co_94_PU

iTrader: (-1)

You are going to have to get on there with a stethoscope, a long handled screwdriver or wooden dowel serves the same purpose when pressed against various surfaces and your ear (put your thumb on the near side and then against your ear) to isolate sources.

​​​Audio of a vehicle is not going to tell "us' much from here to much background stuff happening saturates the audio, add in the compression/conversions and its clear as mud unless there is a serious loud and abnormal sound.

Sounds pretty normal, there is the tickking/clatter you described but we won't be able to isolate it to a part without being able to touch it. Could be just about anything and anywhere (definitely louder on the side you indicated..)

v0lume4

Thanks very much. I have the OEM exhaust, so I will look into the heat shield very soon.

Fair enough. I appreciate your help.

Per your recommendation, I used the screwdriver-as-a-stethoscope trick this morning to try and further narrow down the source of the noise. I can hear the clatter quite loudly at the cat. In addition, I can also clearly hear it on the exhaust pipe feeding into the cat. It is difficult to know whether the sound is coming from the cat, or further up. After some further research, I ponder if the issue could be an exhaust leak.

Would you answer something for me? Are there any particular things I should be looking for while visually inspecting my exhaust system? Just cracks?

Co_94_PU

iTrader: (-1)

Listen to something farther up the exhaust, like the crossover and exhaust manifold. The basic idea is to find the loudest spot, so if it gets quieter when you move forward its likely going to be something on, in or near the catalytic converter. Try along the floor, transmission also.

Yeah cracks or rust, but also loose bits (shake it, tap on it). Watch for discoloration on or around the pipe and joints, they can indicate leaks. Also steam/vapors if it is chilly enough.

v0lume4

Noted. Will check soon -- maybe tonight if it isn't too cold. Thank you.

Kolton5543

Seems like maybe an exhaust leak at the cat.If its some thing in the cat rattling you can tell by smacking it a few times with the engine off. If its coming apart and rattling youll here it.

v0lume4

Will do that as soon as I can take the heat shield off. I tried banging the cat with the heat shield on but didn't hear anything. Seeing that the heat shield takes the impact, I'm not convinced quite yet.

Funny story -- when I was banging around the bottom of the car yesterday, it set off the car alarm and scared the crap out of me. That horn is LOUD from underneath!

75w90mantraN

How much you pay for that low-mi 4runner? Nice catch

I used to have rattling noises under by the cat heat shield. For me, it happened whenever starting to roll and mostly in 2nd gear rpms. Doesn't sound like but yeah, who knows. Sounds fine to me if nothing else going on.

v0lume4

Thanks very much! I paid $8.5k for it. A lot of the 4Runners with 100k+ in my area were running about $6k, so I didn't find it too far overpriced. Besides, there were so many other people asking the seller about the car that I knew I had to scoop it up while I had the chance. I will totally pay $8.5k for a car if it'll last me five years or more with minimal issues. Heck yes.

I'm really just trying to be preventative, that's all. Perhaps to a fault. Local mechanic says that he doesn't think the sound is anything to worry about. I just want this car to be in it for the long haul. Will definitely check this weekend and see if I can pinpoint the noise. As long as it isn't an issue with the engine, I'll be at ease. People say that these engines are a little clattery to begin with.