Benzman33

Hey guys, haven't seen a thread like this yet. This is a place to post Common issues for the X166 and what to look out for when searching to buy a X166. Post below your tips to help future buyers!

WinterPark321

Off the top of my head, here are my issues that I've had on my 2013 GL550. This all occurred around 75k
-Cylinder 5 Misfire. Solution: replaced heads, and a plethora of miscellaneous parts that came with engine disassembly/assembly at dealer.
Link to my thread I made: https://mbworld.org/forums/gl-class-...re-solved.html
-Door lock actuator(s) broken. When the car was locked, without the key, I was able to open door(s). Alarm came on soon after. Solution: replaced lock actuators at dealer
-Air Intake fabric hose broken on both sides of engine. Replaced them

Will update if I remember anything else.

arsupisemnet

Depends on the engine but as it been seen around most of m278 V8 biturbo are having cylinder scarring as close you get to 100k miles... The diesel 350 has well known oil cooler leak there you have to take top of the engine out to change seals... Transmission and transfer case so far so good... Air bags air struts will last up to 120k but replacement in imminent... Lots of plastic pipes - those will snap easily older car gets (reason for old cayennes being ridiculously cheap)

Chedman13

@WinterPark321 - is it possible for you to post your receipt again of your rear door lock actuator repair? I'm having the same issue and I just got it back from the dealer with just a firmware update and it's still happening. You posted it before but the google drive file has been removed. Thanks!

https://mbworld.org/forums/gl-class-...ng-locked.html

mcoady1

X166 is generally a solid car and is much improved reliability-wise to the x164 in regards to air suspension and other components (or maybe just my experience). My x164 had repeated issues with struts, intake manifold, steering fluid components, and rear shocks--all by 85k. Things I've seen on x166's to be aware of/look out for:

M278

• Scoring: As pointed out by arsupisemnet, cylinder wall scoring seems to by an issue on some. There is a TSB on engine serial numbers affected, it seemingly is late 2013 and 2014's if my memory serves me correct (double check). Mine is a early to mid-2013 model outside TSB range with 112k and hasn't had any problems with this in particular.
• Timing Tensioner and Check Valves: common many 2013 and 2014's (likely others). I've never gotten a clear answer as to whether this causes issues or just sounds terrible. Mine hasn't been replaced at 112k and rattles for about 1 second when I turn on and is fine. Even the dealership said not to worry about it causing issues, indy said if it is more than a couple seconds to replace them.
• Engine Harness Oil Contamination: I haven't had it happen but I've seen users post about this issue which apparently requires engine removal and a host of weird issues.
• Misc:
  • Mine is having an injector off balance on cylinder number 7. It's a little rough at idle sometimes and I'll get it replaced (causes downstream oxygen code) but haven't felt like getting it done.

General Car

• Typical Mercedes joys:
  • Blind spot monitors may throw inoperative signals around 100k
  • Engine mounts, fail all over the place mileage-wise. Some at 30k mine have never been replaced and are mostly fine (warm climate).
  • Front end suspension components such as bushings may go out around 100k as this is a big car with a lot of power.

Otherwise it's been a solid, well-built car. What I used to do, and still do when paranoid about cylinder wall scoring, is go through carfaxes of high mileage x166's nation-wide. Many of them are dealer serviced and have details of all repairs. There obviously are many repairs that weren't recorded for a host of reasons, but it's something publicly available. Example: https://www.cars.com/for-sale/search...51683&zc=77001

Chedman13

To your point, carfax didn't even catch some oil changes I did at the dealership.

I always try and get a VMI from the dealership which shows the full history.

WinterPark321

My bad. I just updated the link. Check now. @Chedman13

Chedman13

You rock thanks. This will help my dealership. Holy cow, 135 mb 3 page receipt =) you must have like some super high end scanner!!!