Noisy S50 tap / knock

[RobertK]

Ever since I rebuilt my S50 I have this phantom noise that sound like a mild knock when I start the engine cold but after 2~3 mins it becomes a very quiet tapping / slapping noise and it can only be heard between 900~1500 rpm. The engine runs great otherwise, very strong, with no hesitations or hiccups, no CEL. The noise has been the same since day 1 and never changes no matter how hard I run the engine or how long. Its been doing it for about a month now. (Will post a video later this evening)

Engine has brand new lifters, new main tensioner, rod and main bearings, rings, and rebuild VANOS with new Besian seals and anti-rattle kit.

I was told to try a new spring washer, intake sprocket and sec. tensioner but all those parts look to bein great shape.

After reading this (http://www.r3vlimited.com/board/showthread.php?t=255807) I am beginning to think timing might be slightly off. We used the instructions from the BMW TIS to set timing but it never seemed to line up with the original oil stains on the sprockets.

Before I crack open the valve cover again I was hoping some of you might have some other advice / opinions.

[vandy]

Are you running A/C? I read something about a bolt from the A/C compressor bracket interfering with the motor innards...

[RobertK]

Are you running A/C? I read something about a bolt from the A/C compressor bracket interfering with the motor innards...

I have the A/C bracket and pump mounted but the A/C is not yet hooked up. First I've heard of that though. Shouldn't be any different that it being mount in an E36.

[RobertC]

Taking a quick guess since the noise presented itself After you rebuilt the engine

Stock Bores, Stock pistons, you honed the block to seat new piston rings, you now could have piston slap. Totally common and one of the reasons I will no longer build any engines reusing the stock pistons.

Very well could be a sloppy chain setup if it was not done correctly. Either way, disassembly required. Hopefully its just a matter of resetting the timing chain.

Good Luck

[RobertK]

Videos I took today.

Cold Motor ~ Just Started

http://www.youtube.com/watch?v=PQDoVmVF6U4

http://www.youtube.com/watch?v=UwuGz5xfYzM

Warm Motor ~ After 15 mins of driving

http://www.youtube.com/watch?v=o31FNQy-ybs&feature=plcp

[RobertK]

Taking a quick guess since the noise presented itself After you rebuilt the engine

Stock Bores, Stock pistons, you honed the block to seat new piston rings, you now could have piston slap. Totally common and one of the reasons I will no longer build any engines reusing the stock pistons.

Very well could be a sloppy chain setup if it was not done correctly. Either way, disassembly required. Hopefully its just a matter of resetting the timing chain.

Good Luck

I certainly hope not but with my luck so far with this engine, it wouldn't surprise me.

[RobertC]

Ya that is not piston slap, that sounds like its in the chain assembly.

You should be able to clearly hear where its coming from with a mechanics stethoscope.

Either way it sounds like you got some problems in there. Best to crack that valve cover and recheck your timing chain for slack/slop, probably right between the 2 cam gears.

I get an error when trying to view the 'warmed up' video.

[RobertK]

Fixed the warmed up video link.

Weird that it resonates more in the top middle of the motor but you can hardly hear it from the top when its warm, just get a little bit of noise if you listen under the intake manifold or under the car.

I'm really starting worry that it could be piston slap since people say it goes away when the car warms up.

[e30shmobberr]

my s50 sounded like a diesel on cold start when the oil pump was starting to fail, but not yet failed. I had a fully refreshed head too.

possibly something like this problem?

[RobertK]

my s50 sounded like a diesel on cold start when the oil pump was starting to fail, but not yet failed. I had a fully refreshed head too.

possibly something like this problem?

Oil pump was replaced with a rebuilt one when I rebuilt the motor.

[RobertK]

Just tested, disconnecting the VANOS does nothing to change the sound.

[Robert]

Sounds like the timing is off, that's what it sounded like when we had the timing off on a 318, sounded like a knock , fixed the timing and the noise went away.. Double check the timing.

[reelizmpro]

On my m52 the spark plugs worked loose. Keep it simple.....hopefully its something easy.

[RobertK]

Sounds like the timing is off, that's what it sounded like when we had the timing off on a 318, sounded like a knock , fixed the timing and the noise went away.. Double check the timing.

When your timing was off, was it off on the main tensioner or on the secondary sprockets?

[Robert]

When your timing was off, was it off on the main tensioner or on the secondary sprockets?

It was off on the sprockets , we resealed the motor and the timing on the cams both intake and exhaust side were slightly off.