Is this "emulsification" something to be concerned about? I also had a full service last month and the coolant/temperature light came on earlier this week, then went off and hasn't come back on since. It was below the min line so have had it topped it up today with water.

Some have said its a sign that stop leak has been put in the reservoir, others have said its the silicone packet, but the tank doesn't say "mit silikat" which it apparently would've if it had it in there...

First of all: Emulsification is a process whereby a fatty substance mixes consistently with a watery liquid. An example of emulsification is the production of mayonnaise. (oil and vinegar) You can sometimes see it on the filler cap (a coffee-with-milk-coloured slurry) of your valve cover (often a result of condensation water mixing with oil). You should take a closer look at the composition of your coolant, for example.

When your engine is running, do you see air bubbles appearing in your expansion tank? This could indicate that you have a leaky head gasket.

Furthermore, there is sufficient information available on this subject on the forums of various other car brands.

On 21/09/2025 at 16:34, Agent327 said:

First of all: Emulsification is a process whereby a fatty substance mixes consistently with a watery liquid. An example of emulsification is the production of mayonnaise. (oil and vinegar) You can sometimes see it on the filler cap (a coffee-with-milk-coloured slurry) of your valve cover (often a result of condensation water mixing with oil). You should take a closer look at the composition of your coolant, for example.

When your engine is running, do you see air bubbles appearing in your expansion tank? This could indicate that you have a leaky head gasket.

Furthermore, there is sufficient information available on this subject on the forums of various other car brands.

I've been down this road of a headgasket myself - The big sign was bubbling of the coolant with the engine running and the expansion tank cap off. Rule out the EGR cooler first by bypassing it in the coolant circuit. If the bubbling stops then its the EGR cooler if it doesn't (like me) then it may be either a cracked head or a headgasket - Is there any coolant on the floor or steam from the exhaust? You can get a sniff test done to see if there is any exhaust gasses in the water system.

My problems started with a small loss of coolant every so often - Then we were going to go on a road trip and had the timing belt and waterpump changed. It all went downhill after that. At the end mine had massive pressure in the system, using about a tankful of coolant every 80 miles, steam from the exhaust and an odd hydrlock on startup. Mine was blatantly obvious - No question about it🤣