Engine "knock" sound when it warms up

[jaits]

Hi all,

I have a 2013 brz with around 103,000km. I have owned the car for 4-5 months and have driven about 3000km. Since my ownership, I have noticed a strange knocking/ticking noise from the engine when it warms up, most noticeable at 1500-2000rpm when coming off throttle. No performance issues, just an annoying sound that keeps me up at night

(The video demonstrates me going from 1st to 2nd and coming off throttle at 2000rpm. The noise can be heard at the 10 and 20-second mark of the video.)

I have taken the car to a shop last week to get the issue checked along with doing the 100,000km service. (replacing spark plugs, clutch and brake fluid, pcv valve, engine oil, etc) The shop could not find the actual cause of the noise unless they take stuff apart, but they have done inspections to ensure that it is not due to heat shield, transmission, or drive train issues. They have recommended using a thicker 5w30 oil to see if it has to do with the timing chain, and also added fuel system cleaners and recommends trying higher octane fuel (94 instead of 91) to see if anything changes. Unfortunately, the noise is still here.

Here are a few characteristics of the noise:
- The knocking does go away when I push in the clutch
- The noise is not present when revving the car in neutral at a standstill.
- However, the noise can be heard while coasting in neutral coming to a stop, and I lightly rev the engine. (kinda weird)
- No noise on the initial drive when the oil temp is still cold. As the temps rise up within 1-2 minutes of the drive, the sound becomes more prevalent. (hence why trying with 5w30 to see if it mitigates the noise but failed)
- The shop has put the car on a hoist but could not replicate the noise in the air

If anyone has experience with this "knock" sound and has some insight into diagnosing the issue it would be greatly appreciated. Thanks yall.

[FRS2017]

Your having a similar problem like me. It sounds like its coming from the engine, but maybe around transmission area.

Its not a spun rod bearing as the shop would of picked that up.

[jaits]

Did you fix the problem with your car?

The noise sounded like it was coming near the transmission area and I initially thought it was due to a bad bearing or something. But the shop used the stethoscope to identify it was coming from the engine but had no mention of the severe engine problems such as spun rod bearings or rod knock.

[Slowbro]

Try getting your clutch flushed. And replace slave cylinder if you have black particles in the fluid, and the master cylinder if it's squeaking. I found that my (heavy verus) clutch fork likes to rattle if you have some air in the system.

[jaits]

Originally Posted by Slowbro

Try getting your clutch flushed. And replace slave cylinder if you have black particles in the fluid, and the master cylinder if it's squeaking. I found that my (heavy verus) clutch fork likes to rattle if you have some air in the system.

my clutch was recently flushed and the previous owner replaced the clutch and forks 2 years ago. That didn't seem to fix it.

[stacyu18]

did you have the defrost on or a/c

[jaits]

Originally Posted by stacyu18

did you have the defrost on or a/c

No, I don't and I don't usually turn it on unless I have to on cooler days.

[jaits]

Just an update on the noise. The shop has suspected that knocking noise at low rpms is due to some valve clearance issues (prob improper install of shims from the valve spring recall). I have decided to let the shop drop the engine and fix the valve clearance. They were able to spot the passenger side valves out of spec by a tiny bit which corresponded with the side where the noise came from. Besides fixing the clearance, the timing chain and tensioner were inspected to be fine and the clutch and TOB turned out to be new.

Unfortunately, after all of that, the valve clearance was not the cause of the issue and the noise is still here. But since the noise isn't getting any worse or affecting driving I will just leave it alone and not let it get to me as much.

[radroach]

@jaits


I think it's your clutch throw-out bearing. I've heard that sound on the last two bearings that went bad on me, noticeable on deceleration and revving in neutral, it would make a small rattle you could hear inside and out the car. All early 86/BRZ have issues with their factory throw-out bearing and should be replaced with the new part #30502AA150 which is more robust.



https://www.ft86club.com/forums/showthread.php?t=129260

[jaits]

@radroach

That is exactly what I was worried about when I can hear it while revving in neutral now. I thought for sure it had to do with something internal. Now you have mentioned TOB I suspect a possible probability. Even tho the clutch and fork were replaced by the previous owner, Im not sure if they replaced the TOB or if replaced it with the old version. (the shop did all the clutch inspection I never saw any of it)

Do you know where exactly did you hear the rattle from? I was able to notice it in the engine area and pinpoint it to near the passenger side coil packs. And this rattle only appears after running the engine for a few minutes and in operating temp. I don't think temp affects the TOB.

Thanks for the good pointer, cheers.