Coolant loss after recent drain and fill?

Hello,

Last week I changed both my inverter and engine coolant. I did only fill right above the low line as I thought the other line (middle connection line for engine side) was the “full”. Yesterday I noticed that the engine coolant dropped just a hair below the low so about 1 in. I topped it off to the actual full mark but now it has me worried. After driving on the highway for 25 minutes I opened the hood and used my flashlight to check all the vacuum lines, water pumps or any sign of coolant loss. I couldn’t find any evidence that there was any loss. Now I’m thinking I may have coolant leaking into the engine which could result in a blown head gasket.

I just ordered all the equipment to clean/change the complete EGR system as well as intake manifold and set up an OCC. is this even worth doing since I probably have some kind of internal engine problems? Thinking about just selling the car and buying a used RAV4, unless you think I can fix it by doing all the EGR work.

140,000 miles
No codes
No problems
No knocking
No oil burning or discolor
New spark plugs

 

Thanks! I’ll keep an eye on it daily. I haven’t found anything on how much is too much loss to point to the bad cylinder. It has knocked two or three times before, but that was in January, in 20*F weather. nothing else wrong with it.

Does a clogged EGR/ intake manifold system cause loss of coolant?