Purchased in March of 2020 with 56k miles from MB of Chicago. (Day before they went on covid lockdown). Bought this after returning my leased 2018 GLC 43 AMG Coupe.

Great car, love the ride, the power, and build quality. So much that I just did an engine swap and am basically rebuilding the drivetrain. I’m also a c level executive so I can afford a new one but am choosing otherwise. I had a 22ft boat that I hauled around, have towed car trailers with a car on it, basically used this GL550 like a truck.

So here’s how it’s gone since I purchased it.

-rear lift-gate latch went out about a year after purchase. (and then again about a year ago) $200 part

-at around 95k miles I let it warm up outside on a 15 deg day. One of my plastic coolant lines gave out. I had no clue and about 30 mins after I started it I went outside and there was coolant everywhere and my temp gauge was pegged in the red. Took it to a local shop and they charged me $2,300 and 2 weeks of my life. I should have done it myself. Car was back up and running but the overheating caused me problems…

-at 117k miles I started getting piston slap, just a light tapping from one cylinder. No problem just kept driving.

-120k miles replaced radiator(seeping out the top mounts) and another brittle coolant line

-130k miles developed slight shudder at 1800rpm shift changes on low throttle. Transmission flush and fill. Passenger side rear window regulator/motor replacement. Rear airbags replaced

-150k miles engine and transmission mounts,
heater core replacement, air vent motor replacement

-170k miles transfer case timing chain, passenger side rear door latch replacement, battery replacement

-180k miles both side front cv axles and wheel bearings, spark plugs(originals, all but one looked

-197k miles engine finally gave out. Piston slap was pretty loud at this point. I was driving on the interstate doing 70mph when all of the sudden the engine stalled. I put it in neutral and was able to restart it for about a minute then it stalled again and wouldn't restart. Was able to get it along the side of the road and had it towed home. Engine seized.

-bought a used e550 motor. Pulled engine, trans, and transfer case out. Swapped wiring harness, oil baffle, oil pan, exhaust manifolds etc.

- Car runs smooth as silk, super quiet.

Some key things to keep in mind. A weak battery can cause all kinds of electrical issues and pulling the battery is probably the most painful job on a GL. Exhaust to manifold bolts are a pain to get to. Heater core replacement sucks only cause you have to take the dash out. Change your oil every-5k miles, don’t take the chance on running low on oil. If you really like your GL get ready to work on it yourself, every estimate I had from the dealer was over $2,500 no matter how small the job. Buy OEM parts or other quality brands, they will outlast chinese made parts, ask me how I know. To get parts I had 3 sources…first a local import junkyard here in Indianapolis, 2nd online Mercedes Benz dealer parts websites (irony is that most dealers have their standard walk up parts department you can buy parts from and a secret online parts website that they sell parts for 50-70% off retail), and then I also bought from FCP Euro (they source from MB dealers and OE manufacturers with reasonable prices).

Anyone have questions let me know. I’ve spent a lot of time working on and under mine and would be happy to provide guidance/insights.

 

RockAuto is also awesome for parts.

 

...77k with piston slap

I've never even driven a car for that many miles let alone a 100k+ MSRP GL550 with a chewed up piston lol. Did you replace the heater core prematurely or did it break? I just get paranoid cuz I smell coolant every now and then

 

Hey, can you describe that piston slap sound? does it sound something like this (listen carefully at the background noise, not the injectors). Also did you have any other symptoms, like metal shavings in the oil filter, etc?

 

I noticed that I kept having to top off coolant, and when I took it to a local shop, they did a pressure test and said they couldn’t find any leaks and that I was holding pressure. So I decided to really dig deep and see where it could be leaking and it was leaking at the heater core. probably the easiest way to check if it was leaking where mine was is to look in the driver side foot well along the tunnel pull that carpet back from the console and look right there and see if you have coolant that’s running down the transmission tunnel. sorry using voice to text as I’m driving.

 

can you do a video or an audio going around the engine bay with the hood up? there was no shavings or metal in the oil. just obnoxious noise.

 

cold start video

 

dm me and let’s get on the phone

 

Replaced right rear shock and right rear wheel bearing today. Shock was super simple. Trick is to remove that entire rear interior panel and cut a slit with a razor blade to get through the foam, takes just a few minutes vs trying to pry on it.

Wheel bearing was simple unbolt job and took the hub and new bearing to a local auto repair shop. They pressed out the old bearing and pressed in the new one for $60.

 

Thank you for the write-up! I am at 150k on my 2013 GL450, I had what I thought was a piston slap but others noted its frequency aligned more with valvetrain than piston noise. It mysteriously went away after an oil change a year or so ago. An oil analysis came back perfectly fine even when the noise was present.

Questions:
-was the piston slap permanent or only when engine was warm or cold?
-did you ever use oil additives? I use ceratec with oil changes as cheap insurance but who knows if actually helping
-did you note scoring at some point and just keep driving it?
-What were your symptoms for CV axles and wheel bearing? Our 2017 GLS is clicking like hell at low speeds and not sure what it is

This car has really aged well in my opinion!

 

- piston slap was permanent, starting off like what sounded like valve train noise but became louder as I put on the miles. cold/hot didn't matter. If I went underneath it kind of sounded like it was coming from the bottom of the engine too almost like a rod knock but not nearly as loud.

- yeah used ceratec…did not make a difference in sound but maybe it helped it last longer🤷

- with the sound there I didn’t bother checking into cylinder score…I knew it was terminal.

- at low speed the axles will click, like for example one side would do a click randomly at just off throttle but then it would start a roaring sound getting to highway speed. Best thing to do is buy a $50 noise detection device off Amazon. Then you can clip onto the front assembly (do both sides) and drive it to hear where the noose is coming from. I just did that for my rear wheel bearing. In that case I clipped onto left and right side hubs, rear differential, transfer case and was able to easily hear the crunching from the right rear vs the left rear sounding smooth.

 

Great summary and thanks for all of that. Just curious, you say change the oil every 5k miles (which I do on my M273) - were you doing that on the original engine or just the replacement. I would have thought at 5k intervals the first engine would have gone longer?

 

I just followed the recommended service intervals on the original engine, which I think is 10k miles. On this replacement engine and our BMW X5 I am going 5k intervals.

 

Thanks so much for sharing. Have you ever had any oil leakage problems with this m278 engine?
I strongly agree with you that we can find some genuine parts at Mercedes Benz dealer parts websites at good prices, but it seems that sometimes the local dealer only installs them if the parts are purchased there.

 

On the old engine there was a slight leak on one of the turbo cooler line connection point. For that I simply tightened the bolt just a little.

 

Thanks for the reply. You have excellent DIY skills. I could not even find the leaking point myself and had to go to the mechanic for help.
I would like to add one more thing. I once had a problem with the center console armrest cover not (keeping) close. The dealer would need hundreds to repair that, but I bought a Latch Clip from eBay for around 10 bucks and spent around one hour to put that part on. It seems like a common problem, and there are installation tutorials on YouTube about it.