i have a 97 318 i,bleed radiator,new waterpump,new belts,new thermo,engine cleaner,and block sealer.one bolt broke off in the block.was going to extract it but it doesnt seem to leak.using 10 w 40 because of higher miles.If anyone has any ideas it would help.seems to be building up to much pressure and steams out of cap.:help was wondering if it would be the screw in block but it does not leak?