Giving a Mercedes-Benz V6 The Shaft

"RallyWrench" (rndlitebmw) 11/30/2015 at 16:15 • Filed to: Balance shaft, mercedes

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This is what it looks like. This is a well known problem for all the M272 3.5L 4-cam V6s from 2005-early 2008 model year cars. They are otherwise a good engine, but suffer this one glaring defect. Mercedes-Benz only recently acknowledged the issue with partial coverage under a warranty extension, and has lost at least one class-action suit over it.

As the teeth wear, the cam chain slacks to the point that the variable cam timing actuators can no longer meet their targets, thus triggering the CEL with codes for incorrect cam timing (P1200/P0017 & 1208/P0017), usually on the right bank first. It can be very intermittent, and some cars with badly worn shafts will actually pass the cam timing function test in the shop. This is one of the worst we’ve seen, but it doesn’t take much to throw the codes. Mercedes-Benz has issued updated cam solenoid magnets and harnesses which have to be replaced as a first step, but I’ve yet to see this fix one permanently, as they always seem to need the shaft in the end (giggity).

New on the left, old on the right. Sorry for the shitty pic, it looked better on the small screen.

Just take off all this stuff.

Oh, and these..

Then take this thing out and pull the shaft from its hole (giggity).

Going back together, having given it the shaft (giggity).

Smallbear wants a modern Syclone, local Maple Leafs spammer > RallyWrench 11/30/2015 at 16:21

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That’s a fuckload of chain going a fuckload of different directions.

I'm actually surprised that tension can be kept on that and still have the engine turn over. But then I know precisely jack about this stuff.

Takuro Spirit > RallyWrench 11/30/2015 at 16:22

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Didn’t know they made those turbo.

Sovereign, Purveyor of Coupes > RallyWrench 11/30/2015 at 16:25

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So many plastic tensioner chain guides... I feel for whoever owns these engines in about, 10-15 years.

This is what I like to see though, nice job!

RamblinRover Luxury-Yacht > RallyWrench 11/30/2015 at 16:25

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Tooth wear? On MY obscenely over-complicated system with on-cam balance weights? It’s more likely than you think.

deekster_caddy > RallyWrench 11/30/2015 at 16:29

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Ugh ugh ugh ugh. This is one of the very reasons I am not a big fan of VVT engines, at least the early years of them. Good idea with poor execution. That chain looks like a nightmare.

RallyWrench > RamblinRover Luxury-Yacht 11/30/2015 at 16:35

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Everybody fucks it up somehow.

RallyWrench > deekster_caddy 11/30/2015 at 16:38

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Most early VVT stuff is actually much simpler and more reliable. It’s when manufacturers went to multi-cam VVT that things got really complicated. This is one of the easier ones. Still tricky, but better than, say, BMW’s V8 dual-VANOS or Valvetronic.

RamblinRover Luxury-Yacht > RallyWrench 11/30/2015 at 16:38

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It’s typically funniest when the failure is obvious somebody-done-fucked-up stuff, not a banal failure like this that resulted from insufficient overengineering to resolve the issues of overengineering. I mean, that’s just German.

RallyWrench > Smallbear wants a modern Syclone, local Maple Leafs spammer 11/30/2015 at 16:41

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Hey, you know more now! The balance shaft actually acts as an idler for the chain between the banks and bears that tension, which doesn’t help when the shaft is *ahem* too soft.

RallyWrench > RamblinRover Luxury-Yacht 11/30/2015 at 16:54

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True enough. This is common enough now though that I have to wonder how they could have missed it during development. I mean, surely they ran at least a few these to 100k on a dyno then tore them down.

MonkeePuzzle > RallyWrench 11/30/2015 at 16:55

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I saw this picture as a thumbnail, and thought “ooo, I bet this is about an r/c car with a scraper for snow!”

RallyWrench > MonkeePuzzle 11/30/2015 at 17:00

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I wish I was playing with RC cars, it’d beat the hell out of standing at the desk.

RamblinRover Luxury-Yacht > RallyWrench 11/30/2015 at 17:01

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I was thinking things like the soft cam on some Rover V8s. Power loss before 80,000 miles or so, if I remember correctly.

RallyWrench > RamblinRover Luxury-Yacht 11/30/2015 at 17:07

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Well, Rover... I mean, yeah. But Mercedes-Benz ostensibly checks things before putting them on sale, whereas Rover considers that Beta testing.

RamblinRover Luxury-Yacht > RallyWrench 11/30/2015 at 17:09

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(a) Orders cams from somewhere cheap, puts on shelf. (b) Installs cams 3 years later. (c) Cams start failing. (d) WHERE THE FUCK DID YOU GET THESE, SHENYANG? (e) Well, yeah. I think that’s what Nigel did. Probably.

Smallbear wants a modern Syclone, local Maple Leafs spammer > RallyWrench 11/30/2015 at 17:20

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It appears this engine is a minefield of giggeties.

Smallbear wants a modern Syclone, local Maple Leafs spammer > RallyWrench 11/30/2015 at 17:22

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Oh, I get it now... that's the shaft that's missing.

Urambo Tauro > RallyWrench 11/30/2015 at 17:32

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I have a timing chain job coming up in my near future. Luckily, it’s a pushrod engine. :)

deekster_caddy > RallyWrench 11/30/2015 at 21:03

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It stinks because I love working on engines, modifying them etc. I’m not afraid of digging into a problem, but when it comes to these I’m all nope nope nope. I just don’t have time for it.

RallyWrench > deekster_caddy 11/30/2015 at 21:16

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Yup. This is why I like driving a 50 year old car.

You can tell a Finn but you can't tell him much > RallyWrench 12/01/2015 at 13:26

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I was all like “that isn’t going to work.” Then I realized you hadn’t given it the new hard shaft yet.

/giggity