From the life of a journeyman mechanic - the water gets too hot
06/26/2017
Right at the start of work, a passing customer rolled into our workshop with his Mercedes 220 a and had the work order written out in the repair reception. I got my hands on the order and read: "Engine is getting too hot (up to 95 C after a few minutes of driving). Remove and check the thermostat!"
The thermostat was removed in a few minutes and shortly afterwards lay in the slowly warming water of the electric kettle, which we tend to use as a test device for such purposes. An attached thermometer showed that the water temperature was rising.
To my astonishment, the thermostat opened exactly at 73 C, as it was supposed to. This was also the point at which my "thinking apparatus" kicked into gear. The first thing I noticed was that the thermostat was OK. Given the relatively short time the car had been running, the radiator could not have been clogged; nor was it clogged with insects on the outside.
My next thought was that the engine must have been working under exceptional circumstances and generating an extraordinary amount of heat, which the cooling system could not dissipate quickly enough. I was looking for the reason for this in an incorrect ignition setting or misfiring.
Just as I was about to start checking the ignition setting, I looked at the battery and noticed that the terminal of the earth cable was sitting very high on the negative pole. The reason for this was found immediately: The negative terminal was only loosely attached to the terminal and not tightened.
I fastened the terminal properly, and of course also checked the positive terminal. I then went for a test drive in the presence of the customer. Lo and behold, the motor was no longer over 80 degrees. The customer then told me that the built-in radio had been malfunctioning (intermittent) for some time and that the engine occasionally started less easily than usual.
This confirmed my suspicion that the ignition had been intermittent, albeit briefly, and that this was also the reason for the increased cooling water temperature, although this could not be readily explained. It is also not clear to me that the starter motor was able to move at all in this situation. In any case, I was one experience richer, and with the satisfaction of having thought things through to the end, I wished the customer a "safe journey".
This text was taken from issue 17 of the 1957 edition of the magazine "Krafthand".
