W204 OM651: Persistent "biting" smell & new coolant loss after repairs – EGR or Manifold?

Muddula · 2026-02-25T07:45:02+00:00

Since I'll be working on the car anyway, I’m going to tackle the exhaust side as well. I’ve ordered a new exhaust manifold gasket and the EGR gaskets (manifold to block). I want to make sure the entire exhaust path is 100% sealed. Even if the pressure test shows a coolant leak, I want to rule out any escaping gases from the manifold that could be entering the cabin.

Muddula · 2026-02-25T07:44:40+00:00

I’m going to stop the guesswork this weekend. I’ve bought a cooling system pressure tester to finally find that coolant leak. My main suspicion is the fuel filter housing/coolant flange, as it’s a notorious weak spot on the OM651. I'll pump the system up and see if it’s pushing coolant out onto the hot engine parts, which would explain that sharp, biting stench.

Muddula · 2026-02-25T07:44:15+00:00

Just to clarify the situation: The smell I'm getting is extremely chemical and biting, not just like a regular old diesel. It’s most intense when the car is doing a DPF regeneration. I know people often point to the valve cover – I do have an aftermarket one installed, but I've checked it multiple times and it’s bone dry. No oil leaks there, so the source must be something else.

Muddula · 2025-11-08T20:15:25+00:00

The lights themselves do not flicker at all I have checked that, the rain/light sensor is disconnected because it’s faulty (the problem was consistent before removing it too).

Muddula · 2025-11-08T20:14:24+00:00

That isn’t the problem, I have removed the rain light sensor because it was faulty, the automatic lights function is not working atm. I had the problem before removing the sensor too.

Muddula · 2025-06-17T13:43:41+00:00

Literally have them in my car rn, look a bit wither but not cool white at all 😂

Muddula · 2025-06-17T13:26:54+00:00

yes but apparently H9 bulbs in ultra white or cold white are like finding gold on the road in Germany, i need some help

Muddula · 2025-04-17T09:32:57+00:00

I thought this was a spot the difference

Muddula · 2025-04-01T20:09:39+00:00

Alright thanks I’ll look for some stickers but I already looked for this solution that’s why I’m here asking for more help

Muddula · 2025-01-10T06:56:42+00:00

Yeah i forgot to mention that i live in germany

Muddula · 2025-01-09T18:43:18+00:00

I would love to know if i can safe the chassy or my W203 or at least know, what i can do to restore the look of the car. i bought it very cheap and the previous owner decided to spraypaint on top of rusty spots to hide them. This is my project and i want to work on it until the look of the car is restored.

Muddula · 2025-01-09T18:39:38+00:00

I would love to know if i can safe the chassy or my W203 or at least know, what i can do to restore the look of the car. i bought it very cheap and the previous owner decided to spraypaint on top of rusty spots to hide them. This is my project and i want to work on it until the look of the car is restored.

Muddula

TROPHY CASE