1999 BMW 528 overheating

Do this fill the radiator leave the cap off-Now start the vehicle and observe the coolant flow is it moving around -now pinch off the upper hose for a few secs and let go-did the flow increse? Also could be clogged-up radiator.

Blown headgasket/cracked head or block:

Have it block and pressure tested-do the block first to pinpoint a combustion leaking into the cooling system or a gas analyzer to sniff for hydrocarbons at the radiator fill neck.

Pressure test: do not do a pressure test if there's leakage at the headgasket this might cause coolant into the cylinders and lock it up or bend a connecting rod if cranked thereafter. The headgasket should be repaired before doing the pressure test.

If the block and pressure test passes check the following: Thermostat, Pressure test the Rad. Cap, Clogged radiator, Fan clutch, Radiator electrical fan, collaspe hoses, water pump.