[TK_e91_08]

Hello everyone,
I got a really loud knocking noise, coming from the engine, uploaded a short clip to youtube showing it

https://youtu.be/eCwYHA2C1YE

The Car
e91 325d M57TÜ2
Manual Transmission
05/2008 pre facelift
160k Miles on it

I did some repairs just before the clicking appeared:
Thermostats
Added a Freewheel to the generator
replaced the tensioner
cleaned the intake bridge


I did also clean the air intake at the motor using some brake cleaner and a thooth brush. I did let the brake fluid evaporate for just under 24 hours to make sure there was nothing left, however it was not very warm, and maybe there was still a little brake fluid left in the intake.
The motor did not start up directly, needed a few attempts.

The sound gets quieter and disappears as the engine gets warmer.

First guess would be hydraulic lifters, but seems to be very rare at the Diesel engines.

An other point could be the belt system, I did check it for some play, but all seams to be very stiff, maybe a tiny bit in the water and servo pump.

Maybe the air intake cleaning caused some kind of water damage to the engine

Thanks for any suggestion!

Thilo

[TK_e91_08]

Added about a Liter of Oil today, was a little low on it, knocking is much quieter now, but still there. Any Ideas?
Also thinking about adding some hydraulic lifter additive by liquid moly

[213e90n51]

HMmmmm. I remember when I had ticking of some sort it got quieter when i changed to 5w30 instead of 40. And then i started driving it more up to redline and going to the mountains with it. Now its quiet.

[TK_e91_08]

I am running on 5w30 now, will do an early oil change, just waiting for the filter to arrive, but that might help

Doing high revs sounds like something that could either fix it or make it worse really fast, might give it a try, if I cant figure it out

I disconnected the belt system today, and the knock is still there.

Will take a look into the vacuum pump now, but don't think that related.

That would leave the valve System, and maybe a broken cylinder head gasket, I found the sound of a broken one on youtube, the knock was the same, but twice as fast

[213e90n51]

Its weird to say but yeah i remember when i first got my e90 all i did was drive locally and short trips. I didnt redline it that much at all. At the same time it had a lifter tick or some sort of chatter and it wouldnt feel crisp. After driving it more spiritedly and going mountains and autox it feels great.

[TK_e91_08]

My sound might be Lifter Sounds as well, but you normally only get these in petrol cars, not the Diesel ones.

And I don't quite get, why the knock is so slow, much slower than crank or camshaft.

To bleed the lifters bmw holds the rpm at 3000 for 1-3 minutes, maybe that explains, why your noise was gone after some high rpm mountain drives

[TK_e91_08]

Vacuum pump seems fine

Checked the injectors using ista and all values were great

Disconnected the air manifold and took a look at the valves using a stetoscope camera, and it looked good.

Will build everything back together tomorrow and drive around a little bit, hoping to get rid of the knock. I also ordered injectors seals and the valvecover seal and will open up that next.

Any ideas are very welcome!

[TK_e91_08]

A little update, my timing chain was about to break, one link is already broken on one side

[Tambohamilton]

Originally Posted by TK_e91_08

A little update, my timing chain was about to break, one link is already broken on one side

good catch!

Pics please!

[TK_e91_08]

In my case one would have seen the gap between the links just by removing the vacuum pump, and slowly turning the motor.

Did anyone here change the timing chain without removing the engine?

[TK_e91_08]

Here are some better pictures

[Tambohamilton]

Only ever done chains on an N47, and I went with taking the engine out for that since an engine crane was cheaper than a lift! Good luck with it!

[Tambohamilton]

Did you by any chance record the noise it was making, before you stripped it down?

[TK_e91_08]

All further information is in the first post

[Tambohamilton]

Thanks!