Paul,
Fingers crossed it is just timing.
If you do need to inspect & clear the water jacket I fear it will entail more than simply removing the head. Decent access is really only possible if the liners are removed by which time the job is becoming major.
Unfortunately, proprietary items designed to clear systems of accumulated crud are rarely able to shift the solid mass that tends to form in these blocks and it can literally be a job for a chisel.
B…
Bernie