M276 Camshaft Adjuster
05-29-2023, 10:02 AM
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E400 Coupe
M276 Camshaft Adjuster
Hi
Recently purchased a 2014 E400 Amg Sport Plus V6 TT M276, the timing chain tensioners were totally seized so I replaced them both (note check valves had already been installed) Whilst I was rotating the engine by hand I noticed the left bank (passenger side UK) intake camshaft adjuster would slip then jump.
As I'm not getting any DTC code for camshaft etc I assume mine is not bad enough to register the fault but what is the general consensus with these camshaft adjusters, should they be changed straight away ? I'm not noticing any poor running conditions at the moment. (research suggests the locking pin wears the hole concentrically which causes the adjuster to rattle and not lock the adjuster 1:1 with the camshaft ??)
I would really appreciate if anyone has any data sheets showing the procedure of changing one of these camshaft adjusters, timing marks etc ... what position the engine must be in to lock the camshafts and remove the control valve/bolt & Cam adjuster.
Did I read (or did I imagine it) that the left side intake seems more prone to failure due to slightly lower oil pressure at start up...
Thanks for your time
Jon
Recently purchased a 2014 E400 Amg Sport Plus V6 TT M276, the timing chain tensioners were totally seized so I replaced them both (note check valves had already been installed) Whilst I was rotating the engine by hand I noticed the left bank (passenger side UK) intake camshaft adjuster would slip then jump.
As I'm not getting any DTC code for camshaft etc I assume mine is not bad enough to register the fault but what is the general consensus with these camshaft adjusters, should they be changed straight away ? I'm not noticing any poor running conditions at the moment. (research suggests the locking pin wears the hole concentrically which causes the adjuster to rattle and not lock the adjuster 1:1 with the camshaft ??)
I would really appreciate if anyone has any data sheets showing the procedure of changing one of these camshaft adjusters, timing marks etc ... what position the engine must be in to lock the camshafts and remove the control valve/bolt & Cam adjuster.
Did I read (or did I imagine it) that the left side intake seems more prone to failure due to slightly lower oil pressure at start up...
Thanks for your time
Jon
05-29-2023, 03:01 PM
#2
Super Member
The intake likes to be fully retarded at idle so that's where it should be after you shut down. Then rotating the eng by hand should change nothing. The exhaust likes to be fully advanced at idle, but with no oil pressure to hold it while the eng is off I'd assume the gear rotates 20 degrees when first rotating the crank by hand, then all the cams follow the gears.
I suppose the slip and jump is the valve springs unloading. Since there is no oil to lock the cam to the gear it will have 20 degrees of slack. So turning the crank by hand should leave all the cams all fully retarded, but free to advance if they were able. As the valve springs unload they will try to advance the cam, so that's my assumption for what you're seeing. I'd imagine each of pair of springs is trying to advance the cam when they unload but it depends how the next cam lobe in line is positioned, and other factors like friction and accessories like the fuel pump. So I'd imagine, per full cam gear rotation, you get the same pattern of movement each time? On a V6 that would be three possible events and I'd imagine one of them moves the cam more than the other two? Maybe it's the only one that can, or just more pronounced? Maybe two can do it, maybe all three. Your firing order will determine cam lobe position and which is more likely, or not, to try and advance the cam. Then once the springs advance it that little bit, the cam gear will pick up the slack as you turn the crank, and repeat as you go which looks like slip and jump but is really jump and slip. Jumps forward, then slips while the cam gear catches up. Does this sound like what you're seeing? If not then post a video so we can get a better understanding.
So while I can't say for sure since I didn't witness it and can't poke around, I don't believe there is anything wrong with your adjusters.
I suppose the slip and jump is the valve springs unloading. Since there is no oil to lock the cam to the gear it will have 20 degrees of slack. So turning the crank by hand should leave all the cams all fully retarded, but free to advance if they were able. As the valve springs unload they will try to advance the cam, so that's my assumption for what you're seeing. I'd imagine each of pair of springs is trying to advance the cam when they unload but it depends how the next cam lobe in line is positioned, and other factors like friction and accessories like the fuel pump. So I'd imagine, per full cam gear rotation, you get the same pattern of movement each time? On a V6 that would be three possible events and I'd imagine one of them moves the cam more than the other two? Maybe it's the only one that can, or just more pronounced? Maybe two can do it, maybe all three. Your firing order will determine cam lobe position and which is more likely, or not, to try and advance the cam. Then once the springs advance it that little bit, the cam gear will pick up the slack as you turn the crank, and repeat as you go which looks like slip and jump but is really jump and slip. Jumps forward, then slips while the cam gear catches up. Does this sound like what you're seeing? If not then post a video so we can get a better understanding.
So while I can't say for sure since I didn't witness it and can't poke around, I don't believe there is anything wrong with your adjusters.
05-29-2023, 05:14 PM
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2017 GLE350 4MATIC
There was a video posted on this site recently showing the jump.
One problem in the mix is slipped or loose cam position sensor plates.
Browse the W212 section of the site.
One problem in the mix is slipped or loose cam position sensor plates.
Browse the W212 section of the site.
