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Thread: S52 tapping noise coming from block?

  1. #1
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    S52 tapping noise coming from block?

    Hello everyone. I've been having some issues with the M3. The S52 has developed a nasty sounding tapping noise that seems to be coming from the block somewhere, and is very difficult to find with a stethoscope. Initially I thought this noise was coming from a couple failed hydraulic lifters, so I replaced all of them with new parts. I also replaced the upper and lower timing chain tensioners. After completed these repairs, and replacing several failed/failing lifters, I fired up the engine and the cursed noise still remains. I've stethoscoped the vanos unit, injectors, coil packs, all accessories, PCV, EGR, EVAP, and everything else that is accessible from the engine bay. The noise does not appear to be coming from any of these. Drained the oil and there were no signs of metal flakes or plastic chips from the timing system. I have no CEL codes present, and no other lights on the dash. The car idles with a purrrr. No loss in power is noticed. Here are two short videos I made yesterday. The sound you're looking for is the random tapping noise at idle. In the second video, the noise is consistent with revs when under load. Any help would be appreciated. I've all but decided to drop the engine cradle and remove the oil pan just to check it out. Has anyone on here heard this damn noise before?

    https://youtu.be/HTG84SWDIR0

    https://youtu.be/9mMKT5cM99A

  2. #2
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    My guess is rod knock / rod bearing. Sorry to be bearer of $$ news. I'm 75% positive, but let others chime in. I wouldn't be driving it anywhere IIWY. First video doesn't tell much, but the 2nd...ouch.

    I've heard it in Subarus.....like 25% of them...as the EJ257s love to starve rod bearings of oil.


    If I'm right, ensure you actually FIND what caused the oil starvation to the bearing as this might not be the last time you hear that noise. Oil pump, oil pickup, low oil, etc.
    Last edited by wgknestrick; 05-15-2018 at 09:44 AM.

  3. #3
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    What about pulley tensioners and or pulleys.

  4. #4
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    Quote Originally Posted by ovation1000 View Post
    What about pulley tensioners and or pulleys.
    Very unlikely IMO. When they go, its a bearing with a constant high pitched, squeal noise (of the bearing spinning/grinding around a worn race). Nothing to cause the "tapping" ie impacting of 2 parts. Optimistic thinking, but it wouldn't be my first guess given the stethoscope difficulties of finding the location/source of it, and (most importantly) the 2nd video. Maybe if one of the bolts were loose, but again, it wouldn't be my first guess unless they were recently removed for some reason. I assuming the OP went over the entire engine via stethoscope shaft probe from the accessible areas looking for the source of the noise and couldn't find it. That eliminates almost all of the easy-to-fix sources of the noise.


    .....A spun or worn rod journal bearing that no longer fits it's cylindrical shaft on the other hand....Notice how the sound level increases when the engine is under load, then quiets down as he lets off.

    Rod knock sound videos to compare to.
    https://www.youtube.com/watch?v=Gz4myEP42ps

    https://www.youtube.com/watch?v=_0eu9zQiTig
    Last edited by wgknestrick; 05-15-2018 at 11:40 AM.

  5. #5
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    I would be shocked if itís this simple but I had a similar noise not long ago and was certain it was my vanos, come to find out one of my spark plugs was just ever so slightly under torqued (I know I know rookie move) and there was a small compression leak making a knock noise. Tightened to spec and he noise went away. Also found a few horses again Iím sure...


    Sent from my iPhone using Tapatalk

  6. #6
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    Just throwing it out there, you never know.

  7. #7
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    Thanks for the input gents. Iíll have to remove the oil pan to see the condition of the bottom end. Hopefully I donít find what I think it is...

  8. #8
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    I had a horrible noise I thought was rod knocking on my 95, but thankfully it was something else. I ended up purchasing a cheap engine stethoscope and traced it to the AC compressor. I removed the belt and the sound was completely gone. It ended up being the bearings were shot in the compressor. Just something to check.

  9. #9
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    Quote Originally Posted by MikeUSMC View Post
    Thanks for the input gents. Iíll have to remove the oil pan to see the condition of the bottom end. Hopefully I donít find what I think it is...
    I wouldn't worry too much - you seem to have caught it in time, you're more than capable of doing this, it doesn't take THAT long to do, and it doesn't cost much either.

  10. #10
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    Quote Originally Posted by E85STI View Post
    I had a horrible noise I thought was rod knocking on my 95, but thankfully it was something else. I ended up purchasing a cheap engine stethoscope and traced it to the AC compressor. I removed the belt and the sound was completely gone. It ended up being the bearings were shot in the compressor. Just something to check.
    Quote Originally Posted by blckstrm View Post
    I wouldn't worry too much - you seem to have caught it in time, you're more than capable of doing this, it doesn't take THAT long to do, and it doesn't cost much either.
    Thanks guys. After another close listening to this noise, it sounded like it was possibly coming from the block or flywheel. So I took off the oil pan (what a PITA that was) and examined the internals and the flywheel. I found no loose rod caps, no discoloration, no play from thrust bearings, no movement or anything about the flywheel, oil pump nut was secure... the only red flag I saw was some play on the oil pump chain...

  11. #11
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    Remove the oil pressure switch and put in a gauge. Also try running it without both belts (only for a very short time) try that on a fully cold engine and only for seconds.

    - - - Updated - - -

    When you have the pan off, inspect that the oil pick up tube is not cracked.
    Avoid Vogtland Suspensions! Rusted then failed!

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