The Top 5 Mercedes M157 AMG Engine Issues. The Mercedes M157 engine is a 5.5L twin-turbo V8 initially seen in AMG cars in 2011. It generates 518-577hp depending on the model and AMG Performance Package. A tune and bolt-on boost the M157 engine’s performance even further. The truth is, Mercedes’ M157 AMG engine is nothing to sneeze at. With all of this capability, how does the M157 fare in terms of dependability?
Engine Mercedes M157 AMG
This potent Mercedes-Benz AMG engine can be found in the following Mercedes-Benz models:
- 2012-2016 E63 AMG
- 2011-2017 S63 AMG
- 2011-2014 CL63 AMG
- 2012-2018 Mercedes-Benz CLS63 AMG
- 2012-2015 ML63 AMG
- 2013-2018 G63 AMG
- 2012-2016 GL63 AMG
- 2015-2019 Mercedes-Benz GLE63 AMG
- GLS63 AMG 2016-2019
Mercedes M157 Common Issues
Overall, the M157 is a dependable engine, although it is not invincible. However, Mercedes’ M157 engine is quite good for a high-performance engine. The following are five of the most common M157 engine problems, in no particular order:
- Chain Timing
- Plugs for sparking
- Leak in the Valve Timing Cover
- Injectors
- Hoses for coolant
We will go over these 5 typical M157 difficulties briefly in the rest of the post. Each of the disorders will have a few warning signs and symptoms.
1) Timing Chain Issues on the Mercedes M157 AMG
We decided to start with the M157 timing chain topic because it is primarily an issue with early model M157 engines. On initial start-up, oil drains from the cylinder head in 2011 and 2012 model M157 AMG engines. This causes the timing chain tensioner to run dry for a short period of time. This eventually causes the timing chain to strain, necessitating timing chain replacement. Later model M157 engines were equipped with a check valve to prevent oil starvation. On 2013 and later M157 AMG engines, a new timing chain tensioner and guides were also added. As a result, the timing chain issues primarily affect 2011 and 2012 models.
Symptoms of M157 Stretched Timing Chain
Among the most prevalent symptoms of M157 AMG63 timing chain problems are:
- Cranks that are long
- Misfires and power outages
- CEL turned on
- Codes for faults
This is not an exhaustive list of all possible M157 timing chain symptoms. Furthermore, the presence of these symptoms does not imply that the timing chain is to blame. Keep an eye out for error codes. If the M157 is experiencing timing chain problems, fault codes will be stored.
Timing Chain Replacement M157
This is a potentially costly repair. When owners reported problems, Mercedes replaced the components with new ones and inserted the check valves. However, there was no official recall. Expect to pay well over $1,000 for this repair at the dealer or an independent facility. The good news is that it is 2020. Early generation M157 engines had timing chain problems. As a result, many of the timing chains that would fail have most certainly already failed. It’s still something to be aware of because it can be a time-consuming and costly fix.
2) Mercedes-Benz M157 AMG Spark Plug “Problems”
Spark plugs, on the other hand, should not be regarded a major issue. Especially for those of us coming from the BMW world, where we’re used to constant spark plug changes. The M157 AMG63 engine is no exception when it comes to burning through spark plugs. It comes with the territory of owning a high-performance twin turbo engine. This is especially true for M157 engines that have been tweaked and modded. On original M157 engines, spark plugs should be replaced every 40,000 miles. Tuned M157s may need to be replaced every 15,000-25,000 miles.
Misfires on the OEM spark plugs are common in tuned and customized M157 engines. A spark plug gap that is too large, along with greater cylinder pressures, may result in spark blow out. Eventually, the spark bursting out causes cylinder misfires. On strongly tuned and altered M157 engines, cooler spark plugs may be required to prevent pre-ignition.
Symptoms of an M157 Spark Plug
Spark plugs are part of normal maintenance for factory M157 engines. Over time, the plugs lose their efficiency and create misfires, among other problems. Some signs of old, worn spark plugs include:
- Misfires
- Sluggish acceleration and/or rough idle
- Power outage
- Fuel economy has been reduced.
Misfires are typically the initial indication of the M157. Old, worn spark plugs simply will not produce a large enough spark to finish the burn. If the spark plugs are worn out, you will experience severe power loss, a rough idle, and stuttering acceleration (owing to misfires). We recommend replacing all eight M157 spark plugs at once.
M157 Spark Plug Repair
If you skip the dealer, M157 spark plugs are relatively inexpensive. Purchase a set of OEM spark plugs from a trustworthy online retailer. A set of 8 OEM spark plugs costs less than $100 and is a straightforward DIY project. Replacing the spark plugs necessitates working in some tight spaces, but it’s a very simple DIY.
Intervals between M157 Spark Plug Replacements:
- 40,000-50,000 miles in stock
- Only tune – 20,000-30,000 miles
- Heavy modifications – 15,000-20,000 miles
M157 Spark Plugs for Modded and Tuned Engines
As previously stated, spark plugs may be more difficult to install on modified M157 engines. Most stock turbo autos should be fine with OEM spark plugs. If you’re having misfire problems, you could try gapping the plugs down a little. A smaller spark plug gap results in a more intense spark, which is needed to burn the greater air/fuel mixture. It should be noted that lowering the spark plug gap would shorten the life of the spark plugs.
We propose cooler spark plugs for severely modified M157 engines. Colder plugs move heat away from the spark plug tip more effectively. This is significant because a heated spark plug can cause pre-ignition and engine knocking. When severely altered, this is a formula for blown motors. Many of us BMW guys have had tremendous luck using 1 or 2 step colder spark plugs.
3) Leak in the Mercedes M157 AMG Valve Timing Cover
The M157, often known as the timing case cover, is prone to valve timing cover leaks. A drain hole on the front valve timing cover may leak oil or coolant. This leak is usually caused by the timing case cover not properly sitting. Mercedes did, in fact, release a service bulletin for this specific issue, as seen below.
Leak in the M157 Timing Case
According to the service notice, the M157 timing case cover is usually maintainable without the need for replacement parts. Simply reseal the lid. However, because it is a labor-intensive procedure, replacing the parts while you’re in there may make sense.
Symptoms of M157 Timing Case Cover Leak
A visible oil or coolant leak from the timing case cover area is the primary sign of a leaky timing case cover. Often, the leak is tiny and goes unnoticed. If the leak is severe enough, you may observe smoke or smell burned fluid.
Replacement Timing Case Cover for M157
As previously said, it appears that re-sealing the M157 timing case lid frequently works well without the need for replacement parts. You can save some money by going this route. To access the timing case cover, you must first remove the M157 valve covers. As a result, it’s a time-consuming and costly job at the dealer or an independent repair shop.
Finally, if you are a skilled DIYer, we recommend saving the money and attempting the re-sealing yourself. If the job is being done at a repair facility, you may want to err on the side of safety and replace the timing cover entirely.
4) Leaks in the Mercedes M157 AMG Coolant Hose
We are very familiar with coolant hose leaks, and well, all coolant leaks in general, having come from the BMW world. The M157 coolant hoses are prone to splitting, snapping, or simply popping free with age and mileage. Coolant hoses are often simple to fix and do not cause any concern. However, take caution if the leak is severe enough to cause fast coolant loss.
Overheating is extremely damaging to an engine and may necessitate costly repairs. Things will get very hot very rapidly if the engine runs out of coolant. If the coolant loss is severe, consider towing the vehicle home or to a repair facility. In the case of less severe leaks, simply top up on coolant to get it somewhere where it can be inspected and repaired.
Symptoms of M157 Coolant Hose Leak
In most circumstances, the indications of a coolant leak are obvious. Minor M157 coolant hose leaks will most likely result in a few drops of coolant under the car and a low coolant warning. Significant M157 leakage will cause more visible symptoms, such as:
- Coolant in the engine compartment
- Overheating quickly
- Insufficient coolant light
- Smoke
Again, coolant hose leaks are normally not a cause for concern. However, it is critical to monitor the rate of the leak. After losing too much coolant, the M157 will overheat within minutes.
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M157 Coolant Hose Repair
Depending on which hose(s) is leaking, they are often simple and affordable repairs. Most coolant hoses cost less than $75 and are reasonably straightforward DIY fixes. Because the hoses are affordable, it may make sense to replace any hoses in the vicinity as a precaution. Especially as the M157 gets older and more miles are accumulated.
Mercedes M157 Reliability & Common Issues
As previously noted, the M157 is a dependable engine in general. Expect Honda-like reliability and repair costs, but the M157 is certainly more reliable than many high-performance engines. The timing chain, spark plugs, valve timing cover, and coolant hoses are all common problems. Of course, this is not a full list of potential issues with the M157.
Expect additional “common problems” to arise as the M157 ages. That’s just the way high-performance engines work as they age. Nonetheless, the Mercedes M157 AMG engine is a monster. With 500+hp and a solid reliability record, it’s difficult to go wrong with the M157.
