Gray_Panther

2013 M276 with engine ID that falls within recall.
76k miles with oil changed every 5-7k with 5W-40 MB approved oil.

https://youtu.be/lwgVLBwnxS8

User on W166 subforum says it doesn’t sound great and that recall fix should be made before further repair costs ($$$).

juanmor40

Was that a test a few hours off? or overnight, or days off? If that was after just a few minutes/hours, I would look into the appropriate fix base on serial number, i.e. chain tensioners + check valve. See document below

Gray_Panther

Hey that user was you!!
test was done on cool engine in the morning (engine wasn’t turned on in over twelve hours).

I turned the engine on again after one minute of running and the noise wasn’t there.

Just trying to get an idea of severity and if I am able to hold off on this until I can fix at a later date.

Fliplegend

Not hearing anything abnormal during that start. Mine sounds the same way.

CaliBenzDriver

Mb briantly replicated the rattlesnake warning call for incoming troubles.

You car is warning you of what's around the corner. Save money know to prevent unforseen expense.

JC, do you think at that stage the VVT GEARS lock-pins are already damaged to the point of replacement? Like replace passenger intake, both intakes or ALL 4x VVT?

juanmor40

I think the noise has two sources, and likely two different tones. Sure both will sound like rattling.
1 - Chain slapping a bit? --> Reasoning to replace the chain tensioners
2 - Pins sliding out on the worn channel they have created until enough pressure is built? --> Reasoning for a check valve to minimize the time for the oil pump to bring the pressure back to operating conditions

Not sure how to differentiate them ahead of time w/o having to open the timing covers, or even worse taking the head covers off.

What worries me is the progression in the cost of the repair:
1 - Say it is caught early, it may only need: labor, gasket compound, check valve, chain tensioners at worse, $$
2 - Say it is caught in "middle", it will need all in (1) plus likely VVT adjusters, $$$
3 - Say it is caught further along (likely engine will not start, or misfire like crazy), it will need (1) + (2) + camshaft since the tone ring may have already slipped, or even worse there damage to the camshafts. $$$$ (N * camshafts + N * VVT + 2 check valve + 2 tensioners + labor)

How do we explain tone rings (reluctors) slipping on these engines? It has to be vibration related, and I doubt is due to starting the engine or acceleration/deceleration related. It has to be rattling related --> VVT damaged --> missing check valve --> poor oil condition

CaliBenzDriver

Oh yeah, that's new to me, but not anymore: I think you got it, that makes perfect sense. Thank you for enlightening me with this additional VVT game.

The reluctor wheel is built to get the camshaft sensor into crazy positions BUT STILL KEEP the true actual camshaft position not that far off unlike the loose wheel.
This is so clever, it must be part of the original design. This guarantees misfires. Not directly but gently hidden through a corrective map.

The hammering caused by the camshaft jerking freely due to loose pin (no oil pressure) is forcing the VVT sensor wheel to shift towards late.
That causes CPS to feed erroneous position to ECU.
Cam fault about "Correlation" codes!!!

It's nearly unbelievable how the VVT is carefully designed to waste a big collection of parts 👏

Do you think there's a good way to pin down loose sensor wheel to stop that game without valve cover removal 🙄 ?

Ratcheted tensioner upgrade:
for the longest time cam chains used tensioner that could not back down.
These days it's the opposite: tensioners only work when reduced oil pressure reaches them.

Do we have good old ratcheting tensioners available? Maybe with "Taxi or Police" build option, so called "special use"...

juanmor40

I recall @Westlotorn mentioned his friend's car had 3 shifted reluctor wheels, and he "point welded" them to the camshaft. I guess a point or two at 180 degrees will do it.

Recently, Ivan fixed a Pentastar with a shifted reluctor wheel on a NEW camshaft. I do not agree with how he managed to do it (always very creative), but he found his way and he got it working.

CaliBenzDriver

> Start time: STATIC
you know the optional one-way valve that helps prevent startup rattle when oil pressure is all drained back down... right?


> Run time pressure: DYNAMIC
The missing check valve works hard to prevent tensioner from backing down dynamically during cams rotation.
The valve prevents any reverse pressure, oil has no way to go besides out through shaft seal.


> Missing valve creates pressure surges:
Without a ball-on-spring valve, the camshaft counter pressure forces the tensioner down.

The tensioner pressure increase surges the whole oil lines including the VVT gear nearby.

The oil pressure is precisely controlled by ECU solenoid plunger to adjust the VVT Timing.
Not so well controlled with surges.

25¢ check valve more precious than ever.... hurry limited supplies to sell-out soon ​​​​​

I remember when my car was 5kMi new and rattling, the original dealer shop-foreman saying:
" You can ignore this rattle, it's no problem".

This game would be a recall if it was not a carefully engineered feature:
-- How to make millions by saving $1
👏

juanmor40

Love it

CaliBenzDriver

Somebody at Mercedes decided to go forward with a well crafted Bosch feature made available to many OEM's : Audi, VW, Toyota, Honda... BMW most likely.


> WHAT IS IT :
It's a novel way to help the engine self-destruct on schedule. This involves man-made oil pressure chaos by way of pressure surges and managed low-pressures.

• Are you familiar with old banging distribution tensioners?
• How about engine oil distribution drillings?
• How about oil pump low-pressure mode?

Well here we have all the above mixed up to create a nice big pickle:

Instead of using check-valves to keep a steady oil pressure, the four camshafts are used to RAM SURGE the oil conduits.
This pressure surge directly impact the VVT timings plus the cylinders pistons cooling.

If you've had the missing check-valves installed you can relax a bit otherwise take a deep breath.
​​​​​​
The basic chain tensioners used without check-valve are actively back surging the oil pressure.

Without a ratchet or a one-way valve, the tensioner shaft moves in and out forcefully there by acting as an hydraulic ram. It's a counter pump opposing the main oil pump.


It builds reverse pressure above what the ECU managed oil pump is set to currently deliver.

In order for the pump pressure to prevale, the oil flow has to overcome surges.

X-many times per revolution the oil flow changes direction in parts of the engine.
Then what ? ?


> CAMSHAFT SELF-ROTATION :
Like on most engines, the camshafts force the chain clockwise at every revolution. Unfortunately in our case we have basic tensioners
Our camshafts can seriously jerk using the chain slack caused by floppy low oil pressure isn't able to hold.
This is the way some engines are able to "jump time" at that game.

Master Surya : do you think it would be interesting to borescope Bank1 chain TENSIONER working hard or hardly working ?? @S-Prihadi - With a valve likely near normal can we see reduced pressure mode?

The pressure surge disrupts the oil lubrication cooling of Piston No1, camshaft lobes + HPFP* :

• mysteriously heated blue Cyl_1
• melted internal shield
• flash burned black oil
• vaporized oil in intake swamp
• accelerated oil consumption
• camshaft lobes & bearings wear

The pistons squirters use a ball on spring regulator to shut-off during the low-pump output (below 3500rpm says WIS).
The pressure surges can conceivably create a low pressure after squirters are still opened and pressure crosss zero before rebuilding back up.

This pressure yoyo is based on rpm and pump low pressure control. So idling engine in traffic with ECO disabled may be the worst lube period.

$1 valves optional.... is that a replacement candidate for famous "SBC brakes-by-wire" or "Balance-Shaft" debacles...

My stupid 3.5V6 does have these valves yet, I bet this is going to enhance the engine to new levels of drivability.


(* not only W212, orher Bosch designs)

+++++ Sceptical about camshafts...
For those who don't know that "valves springs do rotate camshafts", the rattle is exactly that...: the Camshaft self-rotating and the VVT catching it up.

CW or CCW:
There is zero slack to go anywhere CCW.
The crankshaft obviously does not stop rotating.
The chain is purposely non-elastic.
so it's CW forward using tension slack.


Camshaft and related parts...
Interesting feedback

Entertainment with MB doctor: M276
All VVT pins bad, new camshaft with plate, CPS oil leakers + the re-do timing job!

M276 New camshafts replaced

M278 killer oil lube defect

- This field video let's you appreciate what normal oil pressure can prevent.
HERE: > Over heated pistons expand to score their cylinders!!

- Seriously considering AN OIL-PUMP SOLENOID DELETE to disable the "half-pressure mode".

- We know it disables piston squirters because of 20psi spring valves... nothing good about that besides we can learn from this.


++++++++ Owner Options ...
1- Either you do both (Tensioners/Valves) every 50kMi

2- or later you'll need the previous items in addition to :
4x VVT for loose rattle
4x Intake Camshafts WHEEL for timing codes

Less VVT can save money but concider they all have nearly similar wear.


++++++++ C-Valves need tune-up!
The above highlight the importance of this check-valve.
Noticed the threads for removal ?
Noticed the weak construction ?

The valve shut-off ball keeps getting banged on a weak seat surface that can't take that sort of beating. It's going to leak back pressure and act as if not installed...

I think it's a good great idea to RENEW EXISTING VALVE WITH the both TENSIONERS every 50kMi. The leaky valve kills the shaft seal by allowing shaft to travel. The seal itself actually acts as a guide bearing. The shaft diameter is not straight so it is not tight inside tensioner bore.

This whole mechanical system is built designed with extreme details like good electronics.


++++++ LOW-PRESSURE PUMP output:
Oil lubricates friction and cools by transferring heat around.
- Why do we need a low-pressure vs. normal pressure mode ? - What does that help accomplish here?

> Low pressure is more easily overcomed by surges. This creates a serious "pressure yoyo" for VVT

> The low pressure mode practically shuts-off the piston squirters below 20psi. The extreme piston heat vaporises oil black, first class. Expanded alloy pistons score cylinder sleeves 👏

​​​​​​
++++++ VVT Rattles opportunity:
Dealers by having top prices help indy shops thrive when they fix rattling cars dropped at the Lexus car lot.


+++++ CONCLUSION ADVICE:

1-- Deal with check-valves. Renew valves with tensioners regularly.

2-- Disable pump solenoid to get unrestricted basic normal oil pressure (Vediamo trick?)



+++++ mechanical Power harvest:
Using the tensioners as oil pumps is one way of recycling some power from the camshafts springs. Hence the ECU can lower the oil pump pressure around idle.

CaliBenzDriver

By now Google sort of understands my interests. Youtube prompted me to watch Master Tasos pissed off about oil pump pressure control solenoid.
It failed such that pump wasted an engine on low oil pressure.
​

> Take home are :
Valve fail-safe position may fail shutt
low oil pressure can kill the engine
MB pump control valve is not reliable

sample Idling rpm :
​​​​​​limited pressure 35psi
normal oil pressure 47Psi