I noticed the coolant reservoir was bubbling profusely after driving from work, and it appears to drop well below the low marker to almost completely empty on a daily basis. after adding more green coolant to it cold a few days in a row the check engine light came on. I've ceased driving the truck. I cannot see anywhere that it may be leaking. Any thoughts appreciated.
My car has 154000 miles.
My car has an automatic transmission.
If the coolant is not leaking externally then it is leaking internally into the engine cylinder. I suggest looking inside the oil cap or on dipstick to see if the oil is contaminated with coolant. The oil would look milky like chocolate milk if so. The cooling system should be pressure tested to see if it holds pressure and to pinpoint where the leak is.
If you’re unable to find the leak, get some help from a certified technician, like one from YourMechanic, to find the source of the coolant leak and suggest an accurate repair from there. Best of luck.