The 1994 525it is back on the road and seemingly fine.
The water pump's plastic impeller was completely missing. There was NO coolant circulating except for what may have moved due to heat convection.
That is why it took so long for any heat to reach the valves for the heater core
That is why it could not be bled.
Roberto, I did read My525it's thread but did not see a test for the water pump.
You had written me that if the water pump failed, the engine should overheat at idle.
That makes sense to me too, so what is a definitive test for a water pump short of examining it out of the engine?
There must have ben a blade left on the pump while I was trying to bleed it because I removed the upper hose at the radiator and di see some movement.
But the lack of volume in the hose made me suspect the water pump.
THe thermostat seemed to operate properly.
The water vapor was the scary part but there had always been more vapor than I liked to see.
SO...This is what happened
NEW water pump, thermostat and housing, upper and lower radiator hoses, fan clutch and both serpentine belts.
The cooling system was flushed and filled.
I , on recommendation form the mechanic, changed from Mobil 1 synthetic to Castrol GTX 20W50.
This oil is good for short distance urban driving.
It seems to have quieted the valves, which had always been making a little noise.
This morning the car was showing water vapor but so where most other cars.
7:30 am and 52 degrees with dew.
I will closely monitor the coolant level and exhaust.
The mechanic assured me that the head gasket was fine.
There were zero hydrocarbons in the coolant and he can detect 1 part per million.
The oil was pure and clean.
I quizzed him on the possibility of water only entering a cylinder and not contaminating the oil or the coolant.
His contention is that would be impossible because on the compression stroke of the engine, gasses would pass into the coolant due to high pressure
if coolant were able to enter the cylinder.
He is saying that the "Hydrocarbon" test is the definitive test for a blown head gasket.
He also stated that this model car will show a bit more vapor than most cars.
It runs very smooth and very strong.
I put blue tape at the current cooling level and will watch it closely.
I would say that if there is no coolant lose after a few weeks then all is well.
The most striking thing was the condition of the water pump, absolutely tripped clean.
The heater now blows very warm air out of both passenger and driver side.
This is without benefit of a missing auxiliary pump.
THe needle now sits a needle width below 1/2.