Leak or loss of refrigerant from the recovery tank cap 

The cover of the recovery tank or expansion tank leaks when the maximum working pressure is repeatedly exceeded.
In this way, coolant is lost every time the engine is started.
There is no other option than to replace it, and it must be done with another cover of the same pressure that is marked on the cover itself.
The cost of this cap is about $8.00 and should be done every 2 to 3 years.