""The flush should do it good.""

If you don't know this procedure.
To 'back flush' a Volvo Red block:

1.Remove the thermostat and re-attach the upper radiator hose to the engine but leave it disconnected from the radiator.
****I have an old thermostat that I have 'gutted' but with the rubber gasket still on the ring. I put this in place so the thermostat housing seals and the back-flush water dosen't leak over the engine block*****

2. attach a hose to the Draincock on the engine block---it's under the exhaust manifold under #4. A cheap garden hose with the connector cut off works---the cheap ones usually have a smaller inner diameter for a tighter fit on that draincock.

3. devise a way to channel the water that will come out of that disconnected top radiator hose to keep it from splashing the engine compartment----a length of 2" PVC works.

3. turn on the hose and run the water until it runs clear out of that top Rad hose.