Has anyone torn into the timing components of a m276 (m278) engine yet? At 253,xxx miles I've changed the timing chain tensioners but just every now and then I get a heckuva rattle. It cranks and runs fine. I get the following codes:

The pos of exh cam bank 1 deviates from the specified valve. Implausible signal.

The pos of intake came bank 2 deviates from the specified value. Commanded position cannot be reached.

The first code is not there all the time but the second is. I just purchased a GL450 to have as a spare car (needed three rows to haul grandbabies). This will give me an opportunity to get the GLK in the shop and break it down to see what is up. It is now at 253k miles, uses no oil and has always had 7500 mile oil changes using Mobil 1 changed hot. Based on what I've read I'm thinking at least the intake on bank 2 cam adjuster needs to be replaced. Once you remove the covers you can see if the adjusters have issues while turning engine over by hand. I'll start there over the next few days.

I'm thinking with the type chain design they should be good for 300k miles. Any thoughts on that. There is a kit you can purchase off ebay that has all the timing components, new tensioners, chains, guides and all four cam adjusters. I have not decided if I'm going to go with something like that because I'm assuming it is made in China. The cam adjuster from MB is $1000/each
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Jim

There is a kit you can purchase off ebay that has all the timing components, new tensioners, chains, guides and all four cam adjusters. I have not decided if I'm going to go with something like that because I'm assuming it is made in China. The cam adjuster from MB is $1000/each
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never had 1 of those apart but as complicated as it is, i would never cheap out on the parts. dealer or the oe brand vendor only.

Is it possible the lower chain tensioner is the source of the noise. That would mean the whole cover comes off in order to inspect.

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Paul

The cam adjusters on those engines are absolute garbage. If you've got 253k on them you're WAAAAAAAY ahead of the curve.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
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90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
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PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

There is a TSB (Xentry tip) that calls for installing a check valve to reduce rattle on startup. Do you have it?

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Prost!

Yes check valves are installed.

Thanks for replies. I'll eventually break it down to see what is up.

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Jim

Your timing chains are stretched at that mileage, they are only good on average to 170k miles, take the upper cam covers off and show a picture of chain tensioner piston , may be extended too much

Got the covers off. Everything is lining up fine. I did find one of the cam position sensors connectors loose and I may have had a leaking intake gasket. Not finding anything out of line in regards to timing. Bank 1 tensioner is sticking out further than bank 2.

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Jim

Here are tensioners. Bank 1 extends out more than bank 2.

The fault code was on bank 2 cam timing not at desired. Also I was getting an out of range high indication on the intake manifold pressure.

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Jim

Before I started disassembly it threw a check engine light, rough running and smells rich running. Misfire on 5 and 6 and the intake manifold pressure sensor was showing a number higher than spec at idle. I did find a cam position sensor connector may have been loose and one of the intake manifold gaskets had a tear in it (possible leak).

All of the timing marks are lining up. Once the cam hold tool arrives I'll pull cam covers to see if I can tell anything else about it.

The fault codes came up once the wife stopped (engine running at idle) after having been on the interstate running fine at around 80 mph for about an hour.

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Jim

I'm going to proceed with replacing the cam adjusters and all the chains and tensioners. hopefully it will make it another 200k miles.

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Jim

Yes the pictures show your chains are stretched enough to warrant replacement, did a car with same issue, i measure the tensioner stick out 10mm approx, thats enough, on a 278, my own 104 wagon engine with 225 k miles showed 12 degrees stretch, had low torque but high reving power , after changing it lots of torque returned

I had a good day on it today but unfortunately found the #6 cyl intake cam lobe closest to firewall worn. I'll get the passenger side valve cover off tomorrow.

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Jim

I stay on top of the oil changes using Mobil 1 0W40. This engine has 253k miles on it averaging between 70 and 90 mph for most of that time. I've been changing oil at around 7500 mile interval.

rear lobe on #6, or last lobe on intake, bank 2.

This was only lobe like this. I wonder if a failing cam actuator could possibly have caused low oil flow to this lobe?

I meant to mention this is not that much of a job but there is a lot of stuff in the way that has to be removed to get to what you are working on.

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Jim

Cyl 4 also had issues with the cam lobe/roller. I got the front timing cover off and it looks like I am going to need to pull the heads to replace timing chain/guides. I would have come out cheaper finding another good, used engine.

This engine makes me like the 1998/99 E300 m606 that much more.

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Jim