Enter the M157. The engine that’s split the votes. But even with bore score this particular engine managed to pull the roller with 700 horsepower and some 800 wheel torque on 93 pump gas (tuned only by our very own mad scientist!). Dialing in a well managed torque curve prevents issues detrimental to the 5.5L powerplant. Yet, to several Mercedes-AMG aficionados, the M157 has failed!

Imagine the year 2010 and Mercedes-AMG has in its arsenal another duty to provide the masses with its next powerhouse eight cylinder monstrosity. Mercedes-AMG topped the past iteration of the eight cylinder by adding 4MATIC functionality and two turbochargers in multiple offerings launching their 0-60 times to lead against the competition. Mercedes-AMG solidifies its true versatility and daily drivability of Mercedes-AMG models within the specialty niche market it tries to occupy. Don’t take our word for it, see this MotorTrend reference for yourself.

However still, the controversial engine and is all-round nature is well documented to have supporting and contradicting findings of its shortcomings. Here, an E63S sedan YouTube-personality and avid M157 owner and maintainer, continues to experience great usability of his M157 equipped W212 even with cylinder bore scoring. Full video below with the side benefit of teaching you how to change M157 spark plugs (A+++ watch):

Fast forward to 09:33 for the borescope and his findings!

This platform has numerous noteworthy concerns and not all of which in its entirety are listed below:

poorly designed timing chain;
cracked turbo exhaust manifold (upgraded and warrantied replacement turbochargers);
rattling noise at startup;
leaking front cover seals (or the more grave coolant loss from front timing case cover gasket failure);
oil consumption (aluminum block inherently designed to high consumption as it is);
oil travelling through the harness from leaking sensors;
carbon build up from its direct injection design (we also prevent further build up with our catch cans); and
bent rods, either due to over-tuning and/or compounding problems e.g. the piston guided rods, open deck construction!

OKAY yeah that IS A HANDFUL! Let’s break it down.

Early M157’s had terrible timing chain wear, as they used a very un-Mercedes like single link chain. Most early M157’s were recalled for a double wide chain replacement and later models received the upgrade. Seldom do damaged turbo exhaust manifolds incapacitate the M157 stranded on the road! Often than not, manifold fissures can be attributed to mismanaged EGT’s; a preventable case when tuning sense is applied! Rattling noise at startup has been largely fixed and revised early in the M157’s lifecycle (reference: tensioner fix). And, a leak-y front cover seal doesn’t quite paint the full picture does it. One asks how well maintained are these engines that’s been victimized, suspicious is as suspicious does, it should be asked to see if there are other contributing factors! It’s easy to take it at face value but where is the commonality when you need it.

While the oil consumption isn’t isolated to this engine and it’s true several makes and models occupy the road today with varying degrees of oil consumption and burning oil commonality (shakes fist at diesel trucks with smoke stacks!). Oil ingress can travel up the harness and is a silent disease that can cause owners 10s of thousands of dollars in repair. A simple fix is a piggy back sacrificial extensions that allow inspection and heavy insurance prevention for such damage for a fraction of the cost (fix that with piggybacks and save yourself thousands from damage).

Carbon build up is a trait for direct injection engines and a stark reality for AUDI’s TFSI, but not isolated to a specific brand. Once a carbon clean is performed it is advisable to add a catch can to the mix to decrease the chances of it from occurring in the future. And last is the main culprit for damage on mistuned M157s here in lies in the crank and its piston guided rods. The tolerances and spacing of the rods compound the problem areas of the M157.

Let us not get too far ahead of ourselves and gather reminders to put the M157 in its proper place. With its, up to, 550 horses the M157 was and still is a very enticing package for a wide demographic of drivers. The like of which are either a:

retiree needing a luxurious sedan/coupe combo in elite executive form of the S63 or with the added focus on speed in the CL63/SL63 combo where the SL loses the two back seats for more driving pleasure for the bachelor with more money than sense; or a
tasteful individual after a trademark saloon for the everyday drive. Of which, is in the know of how Mercedes-AMG operate especially in the uber-practical, yet sleeper, fashion of the E63 (sedan and/or estate) or the severely impractical CLS63 yet possesses rocket ship-like fire breathing four-door “coupe” performance….with four seats; or a
large family where everyone is all relative(s), perusing in a 7 seater, this is important, non-mini-VAN SUV, GL63; or a
non-sensical military might of timeless legends, Geländewagen, G 63 that has stood the test of time being the quintessential high horsepower off-road performer to challenge and overcome the landscape… of Beverly Hills. Because sense and sensibility in the G-Wagon is the key to lifelong happiness.

How many engines can claim this throne in the same manner as above nowadays. Looming over several mother-Earth targets that the governments have placed to save the world (not complaining). Plus the ever increasing emission caps to adhere to and the “un-”planned obsolescence that has been engineered within each marvel that manufacturers release annually since. YES, the M157 can, definitely, be easily misunderstood. Especially within its own lineup of other Mercedes-AMG derived V8 predecessors and successors that unfortunately outshine it.

Except! Consider the fact that the M157 outclass plenty of other makes and models outside its tight-knit Mercedes-AMG siblings. As other vehicles rot and fail, those that perform due diligence in maintenance as an M157 owner, will mastermind a well-mannered [ limping ] BITURBO-charged BEAST (true statement for most, if not all, Mercedes-AMG engines).

To over-modify the M157, is to place it outside its comfort zone. And if you do modify this car past 900, the stock M157 block will fight a losing belligerent battle. We cannot forget the M157 as the elite street bruiser that it is in stock OEM+ form. There are plenty of models on the road fueled with 87 octane gasoline that it can trash, just don’t provoke its siblings too much.

Surpassing OEM+ territory with modifying the M157 will need major intervention, overhaul, surgical precision, and capital operation just to even allow it to find its feet again. Not all M157s need this type of performance and lunacy, not all owners aim for the same targets, not to say that it is impossible as they definitely DO exist.

Finally, we know the M156 with its imploding valvetrain and problematic headbolt(s) right to the specific engine number. We know the M177 likes to bleed-out oil at its rear main seal as it accidentally, unknowingly, holds its own breath. The M113, well it’s just too reliable to be even mentioned. But, out of all the Mercedes-AMG eight cylinders made thus far however, arguably, the M157 has handled its shortcomings the best. It will “limp” you home using all its 500 plus horses only to do it again tomorrow, and the day after next... Just accept it for what it brings, both good and bad. And to us, how can that not claim a win.

#neverDNF

M157 has failed Mercedes-AMG…

Port Matched Exhaust Yay or Nay?