Checking automatic camshaft advancer on M111.921 Update 16 new lifters still knocking noise

Concerning the M111.921, you would have noticed any malfunction of the camshaft advance mechanism by lack of power. Another common failure is a rattling noise, esp. below 2000 rpm. If your engine does not show these symptoms you can assume the camshaft actuator is in order.
AFAIK, there's no offical paper dealing with disassembly of the camshaft actuator. So if you decide to disassemble it, maybe some people would be thankful if you help out with a manual and pictures.


Just my $0.02

Hi, I changed the headgasket at my car and had no special tools, so this is uncritical. I only can remeber that the camshaft adjuster was a little unhandy to get assembled again but it can be done by every petrolhead with two hands. The big spring can be mounted in the wrong direction but you have a pic so you know what to do; in addition, I think that a wrong mounting of the spring would not have any negativ effect.

Really, please, really really take care about the tensioner of the timing chain. It needs to be fully deloaded from the spring force and the deflection before mounting. If not, the camshaft will break after several Km.
---I wanted to add a video but I can only find them in german, sorry...

If you would like to replace the gaskets from the spark plug hole, the mounting of the gaskets at my engine was really easy by using the tool for changing the bushes from the rear wishbones; in german we call them quitsche buchse (squeaking bushes).

mfg
mb

I used a similar manual for replacing the head gasket and that worked quite well so this well be fine, too. I read really often about "hours" of work; I needed days for that so please do not calculate it to tight, it maybe takes longer than expected.

The underpressure system below the manifold is normally out of order; that means two (or three ?) rubber hoses and one T-shaped valve need to be replaced but these parts are really cheap.

br
mb

Zitat von zr550f

I have the knocking sound that you decribe and was presuming that it was a hydraulic lifter, I would not have notized a lack of power because I drive less than 2000km a year and only to and back (in slow speed with under 2000rpm) from town after shopping, the sound is varies in strength , some time when testing just leaving the engine running when the sound is very loud (working temperature) it disappaers after a while.

From your description I also would suppose that a lifter is bad.
The sound from the advancer has a higher frequency, it is not a *knock* *knock* *knock* but rather a *brrrrrt*, occuring when engine load changes from positive to negative load. The smoother the change the longer the noise will hold on.

Zitat von zr550f

About the special tool, I think I have read somewhere that a such was needed and also if one dicconnected the power to the magnet with engine running it would trigger an alarm in the system and not activating the advancer when plugged in again, and the alarm has to be removed by MB.

From what I know - and that's little enough and just what I read over the years, did not test it myself - that's not true. The malfunciton of the camshaft advancer is of course detected by the ECU and DTCs will be produced, but I haven't heard that after re-connecting the wiring the advancer is not actuated any more. Just the opposite, it is a well known test for the advancer being the source of a noise to disconnect the wiring and check if the sound is still there (if not, the advancer is bad). After re-connection of the wiring in all cases known to me the advancer was actuated well.

Zitat von zr550f

I did notice when my friend had the engine cover of to see if it was possible to detect witch of the hydraulic lifters that was faulty that what I think was a notch that had a lever standing in the middel like the advancer was half engaged, it is by the way not possible to check the hydraulic lifters they all had about 1mm of play and it seems that the have a spring inside of them ( not a very strong one) so if you push them down they spring back against the camshaft

Yes, there is an expander spring inside the lifter which lets it expand until there is no gap between the camshaft and the lifter surface.
The test by pressing the lifter down and sense for a gap can of course only be done on a fully expanded and therefore unloaded lifter, i.e. the lifter must not be pressed down by the camshaft. Also, the engine should have been driven until oil temp reached 80°. This is necessary to fill the reservoir of the lifters with oil. This oil prevents the lifter to be compressed when pressure is applied to it. If the lifter can be compressed then the internal sealing and/or valve is bad.

Thanks for the opportunity to write in English and good luck for your diagnosis and repair sessions!