Hey, so since my service last week my car doesn’t go into manual. It’s also making a loud knocking noise from the top end of the engine. Closest to the bonnet. Managed to use YouTube instructions to reset TCU which works but if I press the engine I little I kind of goes into limp mode and doesn’t have that kick down and power when you want it. So now I took it for a a transmission oil change and they said the camshaft cover has gone in it. Found refurbished ones for around £300 but they refuse to fit. They said they have to buy the part in case it’s wrong. The part is £700 and they’re asking for around £1700 to do the job. My question was, is it not possible to fix it instead? Why does it have to be replaced. The car is only 2018 and has done 90000 miles. Any suggestions and help would be greatly appreciated. The guy explained when one of the valves is leaking it’s not getting enough power so that’s when it shuts down into limp mode which makes sense. So it’s not the gearbox issue at all according to him.
strange thing when seen is was done, it came up with TCM issue. The Mercedes specialist said the tcm is fine it’s because of the camshaft cover being gone is why it goes into that low power mode. This also makes sense as when I do a reset it does go back into manual mode. Last two days it’s been driving manual mode perfectly.
someone please help.

 

Whenever something strange happens on the gearbox, the engine should be tested first. The gearbox is 100% governed by the engine, is just a slave.

My advice, change the broken part at any specialized workshop, used or new, doesn't matter and never again use Youtube reset procedure for your gearbox...

 

yes agreed with you totally, the broken part is the camshaft cover/rockers. Spoke to couple people. Guy in London that fixes these a lot advised buy the whole kit from Mercedes Newcastle eBay page for £1200 and £600 to fit it. I think it’s the best a safest option. Trying to repair it and it goes again in a few months time it’s not worth the hassle.