Hello,I am the owner of a 2014 Mercedes-Benz C-Class W205 220D BlueTEC (VIN: WDD2050041F051926), upgraded from 163PS to 230PS. I'm currently facing several significant issues with the vehicle.AdBlue System: The first problem I encountered was with the AdBlue system. It crystallized, causing the sensors to fail. The dealer was out of stock, so I had a technician disable the AdBlue management. I no longer need it.Coolant Leak: I discovered a coolant leak when I noticed that the interior carpet was soaked. It seems the heat exchanger is likely the cause. I need guidance on replacing it, ideally without completely removing the dashboard. If you have any techniques or detailed instructions with diagrams, I'd greatly appreciate it.Engine Freeze Plugs: The most serious issue is that two engine freeze plugs have blown—one on the block and the other on the cylinder head. Unfortunately, I entrusted the car to an incompetent mechanic who removed the engine to replace the plugs (which cost just €1 each) without identifying the underlying cause of the high pressure that caused them to fail. Although the engine runs, it remains under excessive pressure, even though the temperature doesn't rise (likely due to a faulty thermostat). I suspect the cylinder head gasket might be the issue, or possibly a cracked block. The engine is the OM651.921.Electrical Issue: Lastly, the coolant leak under the passenger side carpet caused oxidation in three CAN bus connectors, leading to a short circuit. As a result, there's no power to the dashboard, no transmission control, and the tailgate doesn't work. The car is stuck in "P" mode, and I'm unable to manually release it. I haven't found any documentation on how to manually unlock the transmission on the W205 7G-Tronic.Could you please assist me with at least one of these problems? I would be extremely grateful for your help.Thank you very much in advance from Belgium.

"Thank you for your patience in reading my message, and I summarized the text using ChatGPT. If you need more information, don't hesitate to ask. Thanks again."

ChatGPT will usually break up your paragraph into multiple paragraphs to make things easier to ready and address. Or when you copied and pasted the text, you lost punctuation and format.

Regarding water in the car, have you cleared the sunroof drain channels (if you have a sunroof)? After 10 years, they can become clogged, causing water to back up and flood inside the car. Has the windshield ever been replaced? You want to check for leaks there before replacing the heater core.

Regarding the freeze plugs, typically freeze plugs protect the engine when you have freezing weather and improper anti-freeze in the coolant. The idea is to pop out the plug before cracking the block. High pressure without freezing water is not enough to pop the freeze plug.

Regarding high pressure, how do you know? What do you mean by "high pressure"? How did you measure the pressure? And what fluid are you measuring? Coolant or oil?

Are you the original owner of the car?

that's a lot of neglect, perhaps not survivable or worth fixing.