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So, in my 2014 GL 450, with 48k miles, the valve guides have failed, sliding around. Apparently there is a TSB about it.
I think I found a head I can test and swap and be in good shape. My question is about how difficult the job is. Does the engine have to be removed?
Do the studs prevent the head from sliding off? I am asking bc I am hoping for a one day swap.
I could not find anything about removing the head when it is in the car, everything I found is with the engine already removed.
I have a 2015 GL550 with approximately 70,000 miles on it. Back in December the Check Engine Light started to come on and off; the code was read and I was told one cylinder had a misfire. This happened several times. Some cables were switched out, but the error would come back.
Finally they took a closer look, and the engine needed cylinder head replacement! The car has been in the shop for over 2 weeks now, and I'm being told it may possibly be ready by end of the week or early next week. Thankfully I bought the extended warranty, and I have a free loaner from the dealership, but it surely seems to be a big job!
Any idea what could necessitate a cylinder head replacement - how did this even happen?
2015 GL550 here with 61k miles. Just purchased a month ago and very exact symptoms. Took to MB Natick in MA and they ran a compression test revealing cylinder head replacement. Now waiting for assessment and warranty claim before the rip it apart. Kind of upset but love that vehicle..
That is a bummer. I feel the same, sucked to write the check, but glad to have it back.
I am not convinced it was the cylinder heads, i have the engine, going to pull it apart. let me know what they tell you.
The rumor from the machine shop i spoke with is that the sleeves on the exhaust valve come lose and rattle. the way mine sounded in end was much more significant than that.
I suppose to a hammer, everything looks like a nail.
thanks all - just read that post. What a hassle!!!
so all in all - how long does the repair take?
also i have CNA exclusionary extended warranty and hoping this is covered.
I came across this technical bulletin on the internet issued in August 2015 for worn valve guides on M278 engines. It doesn't provide any root cause details such as design , material or quality defect. However, it does say M278 engines with serial # 30 128000 and higher are affected.
If anyone knows of the true root cause of the problem, please share with this thread.
Wanted to update the chain here - got my GL back this week.
Took 1 month however due to the tech on vacation and the back and forth with CNA warranty.
Everything got covered except some minor incidental stuff and coolant hoses - came to be about $400 out of pocket.
Guess the warranty paid for itself. The car drives like new, they replaced many other items while in there - thermostat, etc. Let's hope the head doesnt go south again...
I have a 2015 GL550 with approximately 70,000 miles on it. Back in December the Check Engine Light started to come on and off; the code was read and I was told one cylinder had a misfire. This happened several times. Some cables were switched out, but the error would come back.
Finally they took a closer look, and the engine needed cylinder head replacement! The car has been in the shop for over 2 weeks now, and I'm being told it may possibly be ready by end of the week or early next week. Thankfully I bought the extended warranty, and I have a free loaner from the dealership, but it surely seems to be a big job!
Any idea what could necessitate a cylinder head replacement - how did this even happen?
Same here: 2016 GL550 with just about 70k miles. Sounds like that is when this happens. Good thing I got the extended warranty. In the shop now getting both heads replaced, also a leaking coolant line. Lesson learned: Always get the extended warranty!
I took my GL450 in to the German auto repair shop, check engine light on. It was making a sound only when the gas pedal is depressed. The cost to further diagnose the problem: $2300, which doesn’t fix the problem...could it be the cylinder head?
Last edited by KUJHAWK; Feb 24, 2021 at 02:05 AM.
Reason: New info
I took my GL450 in to the MB dealer, no check engine light on. It was making a sound only when the gas pedal is depressed. The cost to further diagnose the problem: $2300, which doesn’t fix the problem...only diagnosis
Not sure what to do...see photo for MB dealer’s write up. Do we diagnose ($2300) and repair to the tune of “thousands” over the $2300 to diagnose? How much will 2 cylinder heads be to replace? It’s out of warranty, so it’s all out of pocket.
others can chime in these approx cost to do something like it. But $2300 just to tell you that you’re screwed and to fork over maybe double or triple that sounds crazy. Maybe try a good Mercedes independent shop with better diagnostic equipment and knowledge.
I took my GL450 in to the MB dealer, no check engine light on. It was making a sound only when the gas pedal is depressed. The cost to further diagnose the problem: $2300, which doesn’t fix the problem...only diagnosis
Not sure what to do...see photo for MB dealer’s write up. Do we diagnose ($2300) and repair to the tune of “thousands” over the $2300 to diagnose? How much will 2 cylinder heads be to replace? It’s out of warranty, so it’s all out of pocket.
If I were you, I would get a horoscope and inspect all the cylinders. I ended up replacing my engine due to scoring in 5. Which is common evidently. Long story I can tell you if you are interested.
Thanks. I'm not sure replacing the engine is worth it...no clue on that cost. We did take it to another shop, they didn't have the right diagnostic equipment. I'll try a German specialist to see if they can diagnose the issue for far less that $2300 USD.
Thanks. I'm not sure replacing the engine is worth it...no clue on that cost. We did take it to another shop, they didn't have the right diagnostic equipment. I'll try a German specialist to see if they can diagnose the issue for far less that $2300 USD.
Maybe a good idea to get rid of it/ trade while it drives
I would interested in what price you get in current condition, i went through the same analysis on mine, before i replaced the engine. I got lucky that i actually needed to replace the engine, as opposed to it being something minor that i paid too much to fix. I would spend the $100 to get at least cylinder 5 scoped, or do it yourself. The dealer told me that 5 very often goes bad. If it does turn out to be the cylinder heads, i can help you with replacements, i spent a ton of time researching those also.
I took my GL450 in to the MB dealer, no check engine light on. It was making a sound only when the gas pedal is depressed. The cost to further diagnose the problem: $2300, which doesn’t fix the problem...only diagnosis
Not sure what to do...see photo for MB dealer’s write up. Do we diagnose ($2300) and repair to the tune of “thousands” over the $2300 to diagnose? How much will 2 cylinder heads be to replace? It’s out of warranty, so it’s all out of pocket.
Sorry, didn't see the mileage if you posted it..What is it?
Valve train noise - means they want to take off your cylinder head covers and inspect valve rockers and hydraulic compensators. Now if your car is close to 100k - you will have to replace those plus replace camshafts. It is well known wear for this kind of engines. (it is even hard to find used camshafts in good conditions)
Interesting thing is that dynamic compression test cylinder 3 and 7 fail - which are opposite cylinders from left and right banks. Anyway find any regular motor shop and do regular compression test (by pulling plugs and using manometer)
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