Is my engine toast

[Sdowell11]

So my engine is basically fresh it's done about 1400 miles since it was rebuilt and i think it's got a coolant seal failure, the coolant is overpressurizing and get occasional white smoke I've spent ages bleeding it over and over again and it's constantly bubbling, not crazy bubbles but doesnt settle, I've done a coolant pressure test and it holds 14 psi after I pressurized it to 15psi so I don't really know what's going on, I'm really trying not to pull the motor could do with some advice. Or things I could try

 

[Jit]

Have you checked the caps?

 

[Sdowell11]

Have you checked the caps?

Rad cap ? What other caps is there ?

 

[Jit]

AST and Thermostat Housing Caps.