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M20b23 vibration sound - over 2000rpm

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    M20b23 vibration sound - over 2000rpm

    Hello all,

    Ive done about 30,000km and i have always had a weird vibration sound that appears to be coming from the lower end of engine.

    no idea on kms of engine, susupect rebuild at some stage due to compression results, but 30,000km i did the following,

    overhauled head, timing belt and tensioner, didnt touch the bottem end at all. everything i put back seemed in good condition.

    I am like 95% confident it is not an ancillary making this noise. it is definitely coming from the engine itself and towards the bottom.

    this isn't my engine, but it is the EXACT same noise and description from the guy.

    I found this youtube from this thread,

    Which talks about the oil pump shaft gear bearings. the little needle bearings.

    Those seem like a complete bastard to replace, engine out on a stand sort of job. I have a spare block here (but unusable) and it looks very difficult to replace those bearings.
    Also seems very unlikely they would give any trouble?

    over 30,000km it has not gotten worse. But my issue is i'm using knock ears to tune my engine and all i can hear is this friggen sound. Also i want to fix it cause its not a nice sound.

    Do any of you m20 gurus have any input here?
    Last edited by e30davie; 02-05-2019, 01:57 AM.

    This exact issue has recently plagued my engine, but it only occurs consistently at around 2k rpms. Above or below I don't notice it.

    I went hunting to try and figure out what it was recently and I actually felt pretty confident the noise was coming from the top end of the engine, I diagnosed it at the cap and rotor. It almost sounds like vibrating plastic to me, which made me suspect the dust cap for the cam shaft seal.

    Part 6 here:

    When I removed the cap and rotor to inspect the dust cover I noticed mine had quite a bit of play and was brittle overall. I should have taken a picture, but the dust cap has a small dowel pin that presses through it and I've noticed the through hole for the dowel pin is now pretty worn out and expanded. I suspect a harmonic vibration in the dust cover directly related to the engine speed is causing the noise...

    Annoyingly, my water pump bearing seems to be going out so I am going to do the timing belt prematurely and replace the cover. That has been my best guess so far


      thanks for the reply.

      Intersting thing is on the m20b23 there is no distributor on the front of the cam like yours.

      My distributor is down on the side of the engine (but its not inuse, as ive got megasquirt with LS1 coils). I still have the rotor and cap on, just no leads attached.

      I suppose it could be a similar issue as the sound on mine is towards the bottom of engine. but the distributor is pretty pronounced i would have thought i would have thought i could hear it coming from it, and mucking about yesterday arvo i didn't think the noise came from the dizzy at all. But It is very easy for me to remove the rotor and that plastic cap so i will give it a go. I really should make a blanking plate and remove the dizzy all together.

      its so weird in that the sound is like a switch. just like that youtube video i posted. sound comes on at a precise rpm. which does point to an annoying resonance.
      Last edited by e30davie; 02-05-2019, 03:37 PM.


        Ok so last night i did the following:

        - Removed the cap and rotor from dizzy. Started it up (not using dizzy remember) - sound still there.
        - I then very carefully put my finger on the spinning distributor shaft and i could definitely feel the vibration through the distributor shaft.

        Remembering that my distributor is attached the to the oil pump gear. on the side of the engine. Not in the front.

        So I'm fairly confident that the needle bearing in the block is the culprit. If it isn't that then it is the oil pump pump itself....

        I have a spare engine that I've taken apart with some photos below. Its been sitting around for a while so it doesn't look great.

        Has anyone replaced this bearing with the engine in the car? Might need one of these.

        Alternatively what about a small amount of grease in the existing needle bearing? might shut it up?

        Attached Files


          Oh damn! Sorry to have sent you on a wild goose chase, I thought for sure that's where the noise was coming from... and frankly, I still wish that's where it was coming from.

          I'll bet you're right about the noise coming from the needle bearing over the oil pump, since the oil pump is submerged I think that would muffle it a bit more.


            haha no worries! Damn stupid mini bearing. to be honest the fan is so loud, and also this annoying noise only seems to happen once engine is warmed up. which makes the radiator fan even louder. I can hardly hear it in the engine bay. but close the bonnet and i can really hear the rattle from under the car.

            A mate of mine had a spare block and has one of those "blind hole bearing removal tool kits". He got out that mini bearing very easily from the top. so no need to take the sump off.

            So i went to the local bearing shop, got a new bearing for it for a grand total of $7. I will try and borrow that tool on the weekend and get it done.

            I plan to get rid of the distributor all together but i will need to buy the little Cap (that also has a needle bearing in it) and also the oil pump drive gear on its own. the Cap is no longer available unfortunately. Until then the dizzy can spin on its lonesome there as long as it doesn't make any noise doing it.


              Hopefully you're noise free by the end of the weekend! I'm going to swap my pesky water pump out and work on addressing mine after that.

              I'm curious how difficult it will be to press that needle bearing back in though.


                its easy to press in a piece of round plastic, aluminium or hard wood dowel the correct size that contacts the outer race the and lightly tap it in to full seat the last bit. obviously need to push in in square to start with
                89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                new build thread


                  Originally posted by digger View Post
                  its easy to press in a piece of round plastic, aluminium or hard wood dowel the correct size that contacts the outer race the and lightly tap it in to full seat the last bit. obviously need to push in in square to start with
                  Ahh, makes sense thanks digger!

                  Just wanted to update this thread, I did my timing belt over the weekend and replaced the cam shaft seal dust cover while I was in there. I'm officially vibration free again, my old cover was worn out and cracked and seemed to be the cause. I'm glad it wasn't that little bearing after all...

                  Any luck with yours e30davie?


                    No luck from me i'm afraid. I did buy a new bearing though, $8 from the bearing shop.

                    I realised a few weeks back that in order to remove that bearing i am going to need to remove the sump, oil pump to remove the oil pump drive shaft. The drive shaft protrudes up through that bearing and thus i cant get it out from the top. the internet is 50/50 on weather this is possible with the engine in the car. It sounds like a shit job either way, thinking ill weld up a frame to support the engine on the chassis rails then just lower the front cross member.

                    I am still not entirely convinced it is the problem though. On the weekend i pulled the distributor out of the hole and found that there is some axial play in the distributor probbaly 2mm or so. and when it is installed one can pull it back and forwards and making a knocking sound. My spare distributor did exactly the same thing though. I am not actually using my distrubtor anymore except to drive the tachomoter. so if i can get the megasquirt to drive the tacho then i will aim to remove the distributor and put the late model distributor drive gear in place of the dizzy. I just need to find one.

                    When i had the dizzy out i cleaned it all up and i shoved some grease in that little bearing, it made precisely zero change the noise. So i am not convinced it is the issue. Probably a timing cover too to be honest. I will still change the little bearing for peace of mind (and cause im a sucker for punishment), But yer the noise is driving me nuts.
                    Last edited by e30davie; 03-18-2019, 03:59 PM.


                      Well I finally got a chance to get onto this. Unfortunately i don't have too many photos but ill add some later.

                      Turns out taking the sump out with the car is not impossible, but quite difficult. After stripping the two bolts on the lower peice between the bell housing and sump (friggen star screws!), I ended up having to drop the sump down a little bit, jack up the engine on the exhaust side (undo that side engine mount), with the sump a little bit off unbolt the oil pump, let it drop into the sump then pull the sump and oil pump out in one.

                      I was able to inspect it all fairly well before complete disassembly and what i found was that there was issues with item 11 on this page,


                      The little washers arent metal and arent rubber, some sort of plastic. one of mine was completely missing, and one was broken in half. I can also see evidence on the oil pump drive shaft where it has been moving up and down (shiny bits and wear on the hexagonal ends indicating metal on metal rubbing).

                      I disassembled the oil pump and found that the machined face was quite scored, i can feel the scoring with the finger nail. I have a spare oil pump which is in waay better condition. so i will be using that. I also have a spare oil pump drive shaft.

                      I am yet to remove that little bearing, but see if i can get to that this weekend.

                      I was able to order those washers/spacers from BMW for $3/each. part number is 11411280950.

                      I got a new sump gasket at the same time.

                      So anyway, now we start the re-assembly. I think i will try and support the engine from above and see if i can drop the subframe a bit. I would rater bolt the oil pump on without the sump in the way. But I havvent looked into dropping the subframe, that might be a bit difficult.

                      anyway, i will report back but finding those missing washers/spacers and the obscure wear on the drive shaft gives me hope that i have found the issue.

                      I have also purchase item 18, which is the gear to drive it. Mine being the M20b23 stil has the distributor in there, but im on megasquirt (with a 60-2 wheel on the front) so the distributor is redundant. The only thing the distributor does is drive the tacho, but i should be able to drive the tacho with the megasquirt.


                        Well its all back together, what a pain in the ass of a job. All seems to be fixed. I have now removed the distributor, converted to the late model gear drive and gear holder. The noise culprit appears to have been the distributor itself, axial play in the distributor mechanism.

                        I actually managed to install the oil pump and then install the sump with the pump completely in place. Lots of places on the internet suggest this is not possible...

                        The trick is to undo the engine mounts and jack up the engine form the AC compressor. I managed to shoehorn some bits of wood under the engine mounts to make it remotely safe. the pan still takes a bit to slide in but with some patience it will go in with the oil pump in place.This allows you to get the pump and more importantly the oil pump drive shaft in place properly. then you just slide the pan in. You can see one of these bits of wood in the photo below.

                        I spent a significant amount of time cleaning the sump and the pump at night....... couple of photos for fun.

                        Has anyone got any idea what the little washers on the oil pump drive shaft do? I found that on the gear end the washer did act as a spacer (it bottomed out on the washer before it bottomed out in the gear), on the oil pump drive end though the shaft bottomed out before the washer was even contacted. the only thing i could potentially think of was that the washers were to somehow stop oil from traveling up and down the shaft? meh, who knows. i put two new ones in anyway but still don't really know what they do.

                        I also noticed that with everything assembled the oil pump drive shaft was able to move up and down inside the assembly. so my comments above about these washes stopping axial movement aren't correct.

                        anyway. back to more fun things like suspension and engine tuning!

                        Attached Files