engine and drivetrain Engine noise...

[PatAllen]

I honestly never heard a M10 running without any mechanical noise, so i may be just parano...

My Automatic 02 just started to make a knocking noise at idle, randomly.

It can do it for 5-6 seconds and then disapear. Seems less present when cold.

Before rebuilding the engine i measured all clearances on the crankshaft, the pistons are new and the bearings too. The bores of the block was perfect. The con rods bushings was stiff.

So i am wondering where the toc toc comes from, especialy since it goes away and comes back, randomly. It is not very loud and one could get confused by a valve clacking noise, which is not.

Other than that the engine pulls strong and does not show any bad symptoms once pushed.

One thing i didnt checked is oil pump presure...there seems to be plenty of oil splash in the valve cover at idle so the presure might be "correct"...oil pump was new when i rebuilded the engine...i made 1000km with it so far.

any ideas ?

[thehackmechanic]

Buy a cheap mechanic's stethascope at AutoZone. I used one to pinpoint a loud oil pump chain and bad rod bearings in my '02. I found it endlessly interesting lying beneath the car and just poking the thing around and listening in on the engine's whirring sounds.

[PatAllen]

Buy a cheap mechanic's stethascope at AutoZone. I used one to pinpoint a loud oil pump chain and bad rod bearings in my '02. I found it endlessly interesting lying beneath the car and just poking the thing around and listening in on the engine's whirring sounds.

interesting...i want to open the engine anyway.

what have you done to fix the rod, you didnt just replaced the bearing shells dont you ?

thanks.

[Arshloch]

You are getting an intermittent misfire on one of the cylinders. Mine does the same thing when it is cold and the idle speed drops a little bit lower that it should be. Toc toc toc is in the cylinder running at its leanest.

[PatAllen]

You are getting an intermittent misfire on one of the cylinders. Mine does the same thing when it is cold and the idle speed drops a little bit lower that it should be. Toc toc toc is in the cylinder running at its leanest.

thats interesting, but i doubt this is what i am experiencing. Engine purr like a kitten and idle is super stable.

The more i listen to it and the more it sounds like a bad rod bearing, even when it is revved the engine wizz without any sounds. There maybe a flat spot on the crank shaft journal.

Ill check anyway.

thanks.

[1972fritz]

did yoou install the gight size bearings i.e .010 under .020 under and did you have the rods reconditioned where they make sure the journal is round.over time rods start to wear egg shaped. just as an example i had a m10 apart and had one bearing that was undersized and one valve guide that needed to be over sized weird stuff can happen

[allbim]

My experience has been that rod bearings typically make noise at high rpm. Main bearings typically make noise at idle speed, but main bearings have to be extremely loose to make any noise and by that I mean more than .010" (.25mm) clearance). I think Arshloch has the right idea, especially if it happens more when the engine is cold and the pistons are still a bit on the loose side.

[PatAllen]

My experience has been that rod bearings typically make noise at high rpm. Main bearings typically make noise at idle speed, but main bearings have to be extremely loose to make any noise and by that I mean more than .010" (.25mm) clearance). I think Arshloch has the right idea, especially if it happens more when the engine is cold and the pistons are still a bit on the loose side.

i confirm it does it hot or cold. I played with the idle mixture up to the point it was lean enough to realy start misfire on all cylinders, and it does not sound any worst other than running realy unstable.

I personnaly never heard an engine making a ping or pre-detonation at idle. A missfire, cause by either lean mixture or bad spark does not produce any sound at idle.

Other than that the idle is perfect and the engine realy feels to me like there is a rod bearing that is wrong, or a small end bush on a rod that is not ok.

Piston to cylinder clearance was perfect when i assembled the engine. New pistons and slightly honed cylinders.

[allbim]

Small-end bushings can make a sound very similar to excessive valve lash and at irregular intervals at idle speed.

I have seen bushings loose in the rod that made that kind of noise.

[Guest Anonymous]

i confirm it does it hot or cold. I played with the idle mixture up to the point it was lean enough to realy start misfire on all cylinders, and it does not sound any worst other than running realy unstable.

I personnaly never heard an engine making a ping or pre-detonation at idle. A missfire, cause by either lean mixture or bad spark does not produce any sound at idle.

Other than that the idle is perfect and the engine realy feels to me like there is a rod bearing that is wrong, or a small end bush on a rod that is not ok.

Piston to cylinder clearance was perfect when i assembled the engine. New pistons and slightly honed cylinders.

Hi Pat!

Congratulations on this latest project. I got tired of reading many of what seem to be a rehash of the same posts and did not follow the finality of your latest project.

I owned and nurtured a similar project. After a rebuild, I struggled with looking for a bearing issue or a lubrication issue, just as has been suggested by others. I would not hear it at a fast idle but it did show up when things were warm or when the idle was extremely low (even when cold). The pump was fine, pressure was adequate and so were the sampled bearing clearances. Using a stethoscope I would have sworn I was hearing piston slap or rod knock. However, in my case, I discovered the oil pump chain had just enough slack so that it could oscillate ever so often and slap a little. I had to shim the pump twice to get the sound to disappear. The engine lived a long and productive life.

htt