I'm with Pete and shucker1.
But take your time and carefully and reasonably think about the value and condition of your car and how long you plan and how long you could realistically expect to drive it If you'd fix it.
Think about what other repairs you expect to come up on your car in the near future, etc.
And seriously put plenty of thought into this following question:
"WHY did the cylinder head crack in the first place?"
What caused it, did the engine overheat? Is there a problem with cooling the engine such as with the radiator, pump, leaks...?
Is it supposed to be a long term fix?
- Then get a "new" or rather tested or untested used head, if the car is really worth it.
Do you just want to drive the car a few more weeks or month and then scrap it and get something else?
- Then you might as well attempt do an "insane" Russian "Cober" style repair and just try to seal it off with the best stuff you can find, "hammer" it all back together and drive it carefully and drive it GENTLY until it eventually "blows up" on you.
Aside from that, if the fix doesn't really work, then - if really need be - it could potentially also run another while on just five cylinders. 6 is more than plenty anyways.You could then consider just shutting the fuel injectors on the affected cylinder off, possibly also slightly loosen the spark plug so it doesn't fully seal anymore ((In order to avoid pressure building up in the cylinder. But if you do, make sure you really have no fuel injecting into the cylinder anymore then! Else you could create a fuel leak in the engine compartment.)). And then "ignore" but monitor and stay aware of all the associated error codes popping up. And then just hope for the best until you have enough money to get something else. Now don't get me wrong, this here is of course NOT a recommendation and certainly NOT at all an instruction, it's merely just stating something of a cheap and desperate last means type of alternative to be aware of, when you make your decision.
Both of these two general choices aren't necessarily "wrong" or really truly "better" than the other depending on the condition and of course the financial and (probably more important) the emotional value of the rest of the car.
But I certainly suggest NOT to try fixing the crack in the head for cheap and at the same time expecting it to end up being a successful longer term repair.
Because it most certainly WILL go bad and probably rather sooner than later and it will then most certainly also cause all sorts of other awfully expensive additional damage when it does.
(If you have valve seats affected by the crack running in there then the affected valves for example could likely be damaged already.)
And by the way, any really "serious" professional type of test after any attempted kind of fix would have to be under pressure anyways. But your "leak test" of course isn't bad for a start and a great cheap quick DIY test.
I had a similar crack on a cylinder head of an old French 4 cyl. Renault diesel engine once but between two cylinders.
But that car wouldn't pass the soon upcoming German and very tough safety and emissions tests without a bunch of other costly repairs including a new radiator, exhaust pipes and muffler, break rotors etc....
So I decided... screw it!
I went ahead, took the "best" and only glue I could find in my cabinet that I hoped would penetrate deep into the crack to seal it off.
So I took this little tube of super glue (not exactly a very good and appropriate glue for this actually), just glued the crack back "together" and bolted the cylinder head back on. Then I also epoxied the leak in the radiator that had initially caused the engine to overheat and to ultimately crack and then I drove the car gently and less often for a little more than half a year until the technical inspections were due and then went ahead and sold it for scrapping to a junkyard and got a little over $50 for it. So I thanked the car and bought a six pack of beer and mourned that beloved cute little red piece of junk that carried me through so many semesters at University.
But despite all surprising success of this cheap and awful fix.
Of course that was NOT the proper way to do it at all!
