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Good day!
Beginner here, really need help from experienced MB owners ) Got GLS 450 with M276 (DE 30 LE) engine. It was a fantastic experience to drive this car, until bad things started to happen.
Long story short: one day I got "check engine" light and fault codes of P0303 (issues in cyl. 3) and P0300(22) (random or multiple cyls), white smoke and smell of syrup. The coolant level got a bit low (not much, still within acceptable levels). So it was pretty obvious that I'm loosing coolant to cylinders, so my car is at repair station now (for almost 2 weeks).
Up to date I did not received any explanation of what could possibly go wrong, engine was borescoped and it shows visual signs of coolant inside cylinders. So the only diagnosis that I'm getting now is "blown head gasket" and the cure is to take off the engine to remove head. I have a couple of question: 1) is it true that engine should be taken off to replace head gasket? 2) are there any other more frequent scenarios of internal coolant leak on this engine? It's a "family car", I'm driving it real carefully, no overheating, ever.
Thanks a lot!!!
It can possibly be done in car, but honestly they are designed to have the drivetrain dropped to work on everything, it is a few subframe bolts,, remove driveshafts, some hoses, and wire disconnections and it can be dropped, as long as you have a lift and a engine cradle. then you have full access to the entire drivetrain, only issue is most people don't have a lift at home.
Thank you all!
After all it was a head gasket. Well, almost. The gasket itself was fine, but it was still leaking because of... scratch on a head surface. Pretty big one. My only guess is that something went wrong during assembly process, dunno really.
If I got it right, it's still not too bad and can be fixed. But, I think, I need some thicker gasket now.
Has this engine been opened in the past? Unusual for this to have occurred in original assembly and have functioned this long.
One option is to take it to a machine shop and see if they can skim all or most of the gouge off. Even if it is not 100% removed, a shallower gouge + new head gasket could get you 50k more miles.
Has this engine been opened in the past? Unusual for this to have occurred in original assembly and have functioned this long.
One option is to take it to a machine shop and see if they can skim all or most of the gouge off. Even if it is not 100% removed, a shallower gouge + new head gasket could get you 50k more miles.
I honestly don’t know—I’m the second owner. But it's true: I’ve been driving this car for quite a while and it’s been fantastic—totally smooth. I guess the leakage was minor, and the reason for the "check engine" light might be something else. We’ve been using E5 gas since May (state law), and maybe the ethanol had a negative impact. By the way, 50k extra miles doesn’t sound that impressive—I’ve only put 50k on the car since 2017 (it’s not my only car). I’m hoping to get a lot more out of it 🙂 The engine is generally in good shape, and even the intake valve deposits are minor.
Still waiting to hear back from the service shop—will update later if we’re able to get it fixed within the allowed range.
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