In which the mighty M156 is taken apart for a $2.00 O-ring.

"RallyWrench" (rndlitebmw)
10/28/2014 at 16:54 • Filed to: M156 OIL LEAKS

2007 E63 AMG, 50,000 miles. Pressurized oil leak at left front of the engine, behind the timing cover. We traced it to a machined aluminum cover for the oil pressure relief piston.

The labor guides specify engine & transmission removal out the bottom, complete with suspension, for something like 20 hours. Fortunately, we found that's not necessary. The oil pans must both come off, so the suspension hangs. Otherwise there's more than adequate access with the radiator & condenser removed & the engine hung from above, saving us loads of time with a dead rack and the customer loads of money. The tricky part is getting the complete timing cover out from under the head gaskets.

See the picture of the failed O-ring on the AMG plaque. It's rock hard, turned from rubber to plastic. Poor Marco Rinas, your great work let down by a poorly specified $2.00 seal.

DISCUSSION (15)

Takuro Spirit > RallyWrench
10/28/2014 at 16:58

At least the o-ring was servicable. Most OEMs be like "Serviced only in $XXX.xx component"

505Turbeaux > RallyWrench
10/28/2014 at 16:58

oh how the mighty have fallen! Little RTV on assembly might have kept that soft!

Actually, why do you think the o ring failed, wrong oil detergency, or a shitty compound?

RallyWrench > Takuro Spirit
10/28/2014 at 17:00

True, but this is stretching the definition of "serviceable" to the limit.

RallyWrench > 505Turbeaux
10/28/2014 at 17:03

I think it's a shitty compound. This isn't the first time I've seen failures like this, and it's not limited to MBZ. BMW N62 V8s have similar seals behind the alternator bracket in a block off for optional oil cooler fittings, and BMW M54 & N51/2/4/5 oil filter housing profile gaskets do the same thing. Not sure why this is the case, but it happens a lot. This is just the most severe example I've yet seen.

DoYouEvenShift > RallyWrench
10/28/2014 at 17:04

Lots of chains and cogs and guides. Oh my.

EL_ULY > RallyWrench
10/28/2014 at 17:17

At least it's servicable. We only get paid 6 hours warranty for front timing cover not only on 4GR Lexus, but also V8's at Volvo. As for the Merc, we get those not too offten. C230's rear shaft seal is more common at l3ast here

RallyWrench > EL_ULY
10/28/2014 at 17:20

F that noise. Warranty for this is 7.7 after the engine is out.

Luc - The Acadian Oppo > 505Turbeaux
10/28/2014 at 17:27

It looks like heat might of been the issue. Standard orings are NBR (AKA Buna or Nitrile) they are good to 212deg F then they start to "bake" essentially they get rock hard and brittle. It shouldn't get that hot where the oring sits but it might get close to the max temp and cause the same problem just over a longer period of time.

FKM (AKA Viton) would probably be better suited, it's good to 400deg F but has all the same properties as NBR just much better heat resistance.

Both NBR & FKM are more than adequate for oil resistance so I can't see oil detergents being the issue. My best guess would be heat is the issue but I'm no scientist so I could be wrong.

Just my $0.02 as oppo's friendly neighborhood oring salesman I felt I should give a semi- educated opinion.

EL_ULY > RallyWrench
10/28/2014 at 17:28

luckyyy! The job isn't too bad but warranty is. At least with extended warranty you pick them for a little more

Racescort666 > Luc - The Acadian Oppo
10/28/2014 at 17:47

+1 I thought exactly the same thing. Looks like a Nitrile or Buna N o-ring, should have called out Viton but probably opted for the prior due to cost. Don't feel bad, as an engineer, I regularly ask suppliers for their opinion of their products. Most of the sales guys I talk to are very familiar with their products.

Luc - The Acadian Oppo > Racescort666
10/28/2014 at 18:03

yup Viton is probably 4 times the price of Nitrile so it would of cost Mercedes like $0.12/ea instead of $0.03/ea. Orings are ridiculously cheap we get our oring from Parker and we can literally get like 10 for a penny or $0.001/ea. there is no reason mercedes should've put in the lower spec oring due to cost I'm guessing they thought the NBR would be adequate.

roflcopter > RallyWrench
10/28/2014 at 18:26

My buddy has a first gen RX7 that is slowly dying because of a similar issue... there's an o-ring for the oil galley between the front iron and rotor housing... the thing leaks a quart of oil every 100 miles(on top of what it already burns, rotarylyfe). Only way to replace that o-ring is to do a complete teardown of the motor... meaning new coolant jacket seals, rotor seals, springs, gasket set, soft bits. Even with doing the labor ourselves that's still a minimum of a $600 job all for an o-ring you can pick up at home depot.

mbfixr > RallyWrench
12/03/2014 at 05:17

Mercedes has an updated o-ring and aluminum cover available. The most critical part of putting that timing cover back on is aligning the reverse facing seal on the crankcase centrifuge. It's attached to the center idler sprocket. This cumbersome operation is hard enough with the engine on a stand. It requires the timing cover to be installed straight in horizontally. Not up from the bottom and in or the seal may roll. Only way to verify its ok is to peak at it through the hose fitting on the front with a boroscope. luckily, I noticed this happened and rectified it before I put the engine back together.

RallyWrench > mbfixr
12/03/2014 at 10:55

Yep, it's a 113 number and no longer has AMG embossed in the cover, which we've fitted. I should have updated this post, but we found that the pressure relief valve had been installed backwards, apparently from the factory. The piston was hard up against the cover, with the spring in the oil passage.

Hellbrugge > RallyWrench
09/01/2016 at 16:09

Hello, I am facing a similar problem with my 2010 E 63 AMG - oil temperature is rising, oil thermostat (or pressure relief valve as you have called it) must be stuck.

Is it really impossible to remove this valve without removing the timing cover?

So much work for such a cheap part - stupid engineering solution!