S212@845

When in for a necessary timing cover reseal I also had the shop address the startup rattle. Their initial diagnosis was to add check valves given the model year of my 2014 E350. When they opened the car up, they found check valves had already been installed. They suggested replacing the check valves and the tensioners as preventative. We did not have a chance to fully check in about their findings before they completed the repair. They did share after the fact that one of the check valves started to separate into an inner and outer part as they were removing it. The car does not have any timing codes, but it is occasionally rough at idle, which we chalk up to possible engine and transmission mounts. The car has only about 65K miles.

Unfortunately, a sound at startup has re-emerged that seems like a delay in oiling. I’m frustrated because if we’d had the chance to discuss the fact the car already had check valves installed, we might have gone deeper when the front of the engine was open.

Do any of you have experience of the car making noise at startup AFTER replacing check valves and tensioners and without it exhibiting any other obvious failures? Should we be looking at the timing sensors, oil passages, etc?

Thanks in advance!

S-Prihadi

If the rattle is loud, usually it is the INTAKE VVT starting to fail at its locking pin.
Read here : https://mbworld.org/forums/e-class-w...led-first.html

These VVT will wear out over time and faster if poor oil change practice, too long aging oil even low mileage per oil change...or oil mileage use too high.

Every car manufacturers have this issue, even Toyota. It took them 3 revision to get it better.
Take it as consumable item, albeit high mileage item

CaliBenzDriver

As pointed out above, the startup rattle originates from the unlocked VVT intake phasers.

The next stage is the loose camshaft wheel shifts away to generate mismatched timing codes.

Practically you have a few options for repairs. Do as little as possible or fix it for the next 80kMi.

A -- Cheapest option :
> This means only passenger-side Bank#1 Intake VVT.

- Save repeat labor: take this opportunity to check cam wheels position looking through sensor ports.

- Valve covers are NOT removed to saves $$$$ labor.


B -- Intermediate option :
> Fix driver-side Bank#2 Intake VVT as well.


C -- Comprehensive repair :
> This means ALL 4x Phasers on both Banks
AND both intake camshafts.

- This option requires labor to pull injectors, HPFP, Plugs, and valve covers...


> ROOT CAUSE :
Low oil pressure is what forces the VVT into locked positions countless times.... so in addition to above repairs, consider deleting the "low oil pressure" control to prevent :

1. loose VVT locking pins and
2. worned camshaft lobes and
3. $8k "oil-in-harness" from baked sensors

This unwarranted step takes 5mn to eliminates all the above aggravations as tested on MY'14-M276.


> URBAN LEGEND...:
The amazing "missing check-valve" causing the engine rattle is a moronic tall tale spread by... MB itself (see YT below).

The root cause is the buggy software feature that forces low oil pressure while driving. That wears out lock-pins, camshafts lobes and HPFP roller.

Restricting lubrication of pistons and cylinders sleeves is source of chaos.

Here the .... go figure


> CAMSHAFT FAILURE :
It's amazing to understand how these strings of defects are carefully engineered.

The tone wheels are pressed on camshafts but loose enough to force camshaft replacement in absence of reference marks.

Its using a soft metal alloy that expends more than the camshaft steel to help tone wheels get loose - That's seriously impressive work from the camshaft manufacturer ! 👏

"The Best or Something"