Hello,

I have found a few threads relating to the 3rz engine having a rattle when idling hot. None of these threads seem to lead to any conclusions. Has anyone any follow up regarding this?

I have a 96 3rz with 140,000 Km. 5spd. Valves recently inspected, all well in spec.

Trouble is: When idling hot, 6-700 rpm. a vague rattling/tapping noise can be heard from the engine. Seems to be passenger side, seems to be low down in the engine. Stethescope could not pinpoint anything specific. This is not the injectors or valves. Seems to be getting worse over the last 10,000 km. Sounds great at any rpm higher than idle, runs very well. No noise at all 'til hot enough to slow to the hot idle of 6-700 rpm. Blip the throttle and noise disappears.

There are several threads here and on some of the other forums but they fail to lead anywhere.

Any info to share? Thank you.

if I had to guess maybe oil pump? the oil pumps in the 3rz can get clogged up and when you increase the rpm more pressure builds and more oil gets through to it.

possibly balancing shaft

Balance Shaft Removal Kit - 3RZ

Thank you for the replies.

With regards to the oil pump clogging. Do you mean the sump screen or do you mean the pump itself? And what would cause it to clog up on a moderate mileage engine? It has had synthetics since new and currently Amsoil signature.

Thanks again. Going to try to buy a pressure test gauge tomorrow.

Well, that took a long while to get to.

Finally got an oil pressure tester and a new oil pressure switch as the old one dripped.

Found my pressure to be good. 14 psi at hot idle RPM and 70 psi at 3,000 RPM. These may not be exact as I bought a cheap gauge but close enough.

I think oil pressure is not my problem. I will update if I ever find the source of my rattle.

I may have the same issue. I'd like to get to the bottom of it as well.

Did you ever get to the bottom of this?

I have a very light ticking sound which comes from the right hand side of the vehicle. Cannot pinpoint the noise. Valves all good and engine runs perfectly.

When I rebuilt my engine I replaced both balance shafts and had newbearings pressed in. Never any swarf or yellow metal in the oil. The noise sounds too light to be deep in the rotating bowels of the engine. Could it be a slow exhaust manifold crack?

Thanks

EO

No, never did. What are we, 6 years later and about 60,000km later and no progress on this front. The noise is still there and it hasn't really changed much. The 4runner works great still.

As I mentioned, it only happens when it is warm out, when the engine is full hot and sitting at idle. In normal day to day daily driving you never really even notice it. Certainly doesn't seem to be an issue. I'm pretty obsessive about maintenance and noises, I don't think the average joe would even hear it.

Back when I first posted this in 2014 I took it to a Toyota specialist shop who have some experience with the 3rz and balance shaft deletes in particular. They listened for a bit and didn't think it was anything unusual. They said they would listen for it on the next 3rz they worked on and let me know but they never did.

I spent a fair bit of time under it with a stethescope that first year. I seem to think it comes from low down and toward the rear of the engine, maybe even bell housing. I have sort of been thinking it might be something in the clutch rattling a bit. Really hard to be sure where it originates.

Things I tried: Changing oil brands, no difference. Changed to the Tacoma mini header, no change. Valves have been checked when I first bought it and fairly recently adjusted,also no affect. I have only checked oil pressure that one time but it was great then so I have no reason to think it is any different now. The only thing that has had any affect was cleaning the AIC valve and TB. This raised the idle rpm up maybe 50 rpm and the noise is a little less pronounced. Any rpm above idle and it is gone.

I have also spent a bit of time snooping beside others with 4 cylinder tacomas and they have a pretty noisy idle too. I'm not sure mine is an isolated case, I think I am just listening for it now while others have never noticed.

In short, I am not sure it is an issue at all. Just going to keep driving it. Please let us know if you happen to find anything.

I've had 5 3RZ's, one with the balance shafts deleted. They've all been noisy at a low RPM idle, I've never been too worried about it and it's never presented any issue.

Sent from my JSN-L23 using Tapatalk

Thank you very much for your reply. Great to hear that your 3RZ is going strong.

I've looked through a number of threads on the 2RZ and 3RZ (I googled '3RZ hot idle tapping') and it seems that the issue is common, though nobody ever gets to the bottom of it.

Piston slap, wrist pin noise and balance shaft noise often come up, but only balance shaft noise would be every second turn of the crankshaft. Also, because I rebuilt my engine using only genuine parts, and had a very goodmachine shop do the rebore, I'm pretty certain that these things cannot be the cause. I have put about 50,000 km on the engine since the rebuild - so it's in that sweet spot where anything majorly wrong would have become obvious by now, whereas the new components are still (hopefully) long away from becoming worn.

The things which I did not replace that come to mind are:

-valve lifters - the valve claearances are still spot-on after 50,000 km but the lifters themselves might be worn. That said, neither myself nor a couple of experienced mechanic friends can really see how a bit of wear on a plain bucket lifter would cause a tap. What did interest me was this review on Amazon for a new lifter. Seems at least that guy cured his problem. At the weekend I plan to run the engine with the valve cover off and see if I can find the noise.

-timing chains and tensioners / guides. Maybe i should have replaced all this, but the chains were still well within tolerance so I saw no need to replace them. I really don't see how a timing chain would make a low frequency tap. From my research, a noisy timing chain makes the engine sound like a diesel when it revs down.

-exhaust manifold - I'll take a hose to my ear and have a listen for cracks - mine is still on the original 1996 manifold - and at the joins with the downpipe. My cat is quite rusty so I'll check there too, but I never smell exhaust fumes near the engine.

-camshafts - again, given the clearances are good, I don't see a reason for a tap.

That's about it. Overall, I think I can sleep easy with this noise. If I do find it and fixit, all the better.

Thanks

EO

Yes, it's definitely a noisy engine at idle, sounds almost like a diesel!

Are you talking about a smooth, even valve clatter, or something a-rhythmical such as the OP and myself are experiencing?