Tick / grinding noise at 0.36x crank rpm.,

My engine (3.4) developed a tick/grind noise especially when cold. It�s audible in the cabin as well as under the car. At 780rpm idle, the tick seems to be 290rpm. Definitely not 0.5x crankshaft, but slower (i can tell cause i also havea noisy lifter everynow and then, definitely the lifter is faster. I�d upload the soundbite but my iphone doesnt let me. Ratio to crank seems to be 0.36:1, anyone have an idea?

Seems like this topic only got approved after it was well and truly buried. Anyway, I figured out what it was by carefully listening to the tick. listened and recorded the sound, measured the periodicity of the grind and determined it to have a 'frequency' of 316 RPM. Now, nothing in the car syncs up with 316 RPM. Idling, my engine runs 780 rpm. Camshafts go 1/2 that, so 390 RPM. The IMS shaft goes 0.67x crank, so 523 RPM. Couldn't think of anything else spinning at this weird fraction, until it hit me; the ***** in a bearing go 1/2 the speed of the races, while the ***** also have a shorter distance to travel because they're on a lower radius (more towards the center, smaller circle than the outer race), so complete 1 revolution 'faster'. Correcting for the lower circumference the ***** have to travel compared to the outer race, which is a factor 1.24, I came out on the ***** inside the IMS bearing rotating with a frequency of 523 (shaft RPM) divided by 2 (***** go twice as slow) times 1.24 (distance in travel between outer race and ***** itself) = 324 RPM . Which is very close to the 316 I measured from the sound. So it's the IMS going. Sounded like this: You Tube

Maybe buy a cheap stethoscope to localize the place where the sound is coming from?

Well I already solved it, it was coming from the IMS and the periodicity of the sound corresponds to the rotation rate of the ***** inside the bearing which is unique in the motor. Nothing else spins at 324 RPM. I just figured I'd post back with the results for anyone looking for it in the future I'm pulling it apart as we speak.

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Gotcha, I didn't know if you were 100% sure or not. Its an interesting way to check for the source of a noise; I wonder if there is some kind of phone app that can spit out the frequency or period of a repetitive clicking or tapping? could be used by others on here to trace the source of noises?

Haha, that's exactly what a friend said who was in my workplace with me when he saw me crunch the numbers after making a spectograph of the sound on my PC. "There must be a way to make an app for that, "IMS Failure Detector" or something". Haven't found one yet, but sure would be useful.

Makes the same sound with the belt off? How did/does the oil filter look? Almost sounds like a water pump grinding against the block.

Yeah I started it with the belt off, suspected the water pump at first. Same sound. Ferritic metal grit and larger debris (1-2mm) in the filter which is only 300km old. All pretty clear :P

Wow....good catch, I think? Do you have the spin on adapter or the OEM filter? What year is your car and how many miles?

I can't believe you ran the car that long hearing that noise. Shut it down and tow it to the shop. Sounds like a bag of marbles in there, which coincides with your IMS theory. Side note, nice work on the math, detective. LOL

Should have been more clear about that; the vid is not mine but someone elses. I linked it as it's the same sound. Car's been stationary after hearing the sound, and is not going to be started before the IMS is fixed.

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PHEW LOL. Well I can't believe that guy ran his car sounding like that. Every rotation is damage. 780rpm Idle, almost a one minute video, he basically was taking a hammer and chisel to his motor 700 times to post that lol. Not smart.

Interesting. Let us know what you find. The video (while not yours) kinda sounds like 1/2 crank speed to me, or at least I would have assumed that. I would never have figured out 1/3rd RPM like you did. If you tear the whole thing apart and it�s the IMS, let us know.

Definitely will, should be coming out this week. But I am really confident in this analysis :P I went all Audacity on my recorded soundfile, and got the frequency from the spectogram. But if you tap along with the vid here, you'll get a general measurement of how many beats per minute (= rpm): https://www.all8.com/tools/bpm.htm

Based on the sound alone, I would have guessed connecting rod bearing.

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Holy Crap!

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Excellent detective work -- I've always wanted to find a iPhone app that would translate noises to frequency so that something like this would be possible. I would never been smart enough to realize the 1.24x factor for the bearing to race multiplier though Mike

Wow, good catch! Lots of cleaning and pull the sump off to look for debris you might have really dodged a bullet there. Amazing detective work, looks like sealing RTV underneath the RMS too like someone has been in there before. Its a single row IMS?

user 63031: When you said it had the noise both hot and more pronounced cold.....was it like the video when it was hot, i.e. very noticeable, or was it quiet when warm and it sounded like the video when it was cold? Great that you caught it.

Thanks for the kind words. It was a dual row, which I guess saved me since it's lodged a bit more tightly on the cover plate. Kept the ***** within the races even though they were eating their way out. A single row would spew the inner race immediately probably, throwing the ***** out and fubaring the engine. @ Paul, the sound started out cold, and would be gone at RPM and hot temps at first. Then it would be there regardless of hot/cold, and at slightly elevated RPM's (1.5k) as well. This evolved like that in the span of a mere 100km driven - at the end it sounded like the video I linked, which is when I parked it. I cleaned all I could, made my stock filter arrangement non-bypass for the moment and am replacing the filter every few 100km for 3-4 times before putting in my more expensive oil (runs Mobil 1 3000 x1 5w40 now).

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Did you pull the sump plate off? I would to check for any chunks of metal in the bottom or jammed in the oil pump pickup mesh, remember don't use too much sealing goop when you put it back.

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That's good stuff and glad you are able to saved the motor! An app would be great since I have no rhythm and ears are bad. That's a great idea for detection.

Awesome An IMS happy ending

Wow I need. Glad you got it resolved and thanks for sharing the updates.