My car has already given me a sensory roller coaster in the few months in which I own it. I hope this is finally over and would like to write why.
Disappointment
I had already told some time ago about the workshop that had sincerely promised me that the cylinder head gasket of my car would be intact.
However, the car still had the same symptoms as before and these have been getting stronger. When I drove to the workshop and asked why I still have the problem after almost 400 euros, they have told me that they can’t help me further and that I should report to Honda.
I called Honda and asked them what the diagnosis would cost and they thought it would be at least four digits. I then renounced it and asked my brother for advice.
The solution
He said that he still assumed that it was the cylinder head gasket. Then he recommended me a sealant. Holts Wondarwelt

Execution
My brother had first let out the entire coolant and then filled a little water.
Thereafter, the sealant was poured in and completed with a residual charge of water. After that, he asked me to drive for a very long time in the car with as little speed as possible.
The connection
One day later, we removed the entire coolant from the car again and renewed it. This time we poured Holts Speed Flush with water. In the next few days I will rinse the cooling system and refill it finally.
Conclusion
It happens again and again that one is confronted with incompetence. The workshop I’ve been in, despite all the tools and resources, has not been able to pinpoint what my brother recognized with his naked eye and experience.
The German car workshops do not have a good reputation anyway and I know why now! My brother solved the problem with 40 euros, which the workshop did not manage with 400!