How to know if I have a blown head gasket

You can rent a chemical tester from auto zone and its really easy to use if it changes color you have exhaust gases in your coolant.

It can be very difficult to confirm. There are a number of test that can be performed including, chemical block test, cylinder leakdown test, coolant pressure test, exhaust analyzer to sniff for HCs at the radiator, observing white smoke out the exhaust or constant bubbling in the radiator. You would need to confirm it through a few different tests.

Have it block and pressure tested

I posted a fairly log answer to this earlier but apparently it never posted although it did start sending me notifications of other responses.

I don't see the actual leak but your picture is of a plastic elbow attached to the belt tensioner that carries coolant. This elbow rots and leaks all the time. When you remove it you will have to dig out the broken pieces from the engine and tensioner.

Pressure test the cooling system as you should have done first.

Its easy just get a cooling system pressure tester and read the operating instruction-it will walk you thru-

Wrench-I use those 4-tests for confirmation-when I suspect a possible internal coolant leak-The most I like is the sniffer type to track HC's its faster atleast for me.

I think that is the best way too but since we don't have inspection in this state, very few shops have one.

Using the 5 gas analyzer will tell you a lot of what's happening with compression, fuel and spark-I wish I have one of my own, cannot afford it, its too much to have-lol I used to be an Emission I/M specialist back in the 80's, now I have the CRS disease, I just go with the flow -Goodnite