Just bought a very nice 1990 745GL. Yesterday I drove it home from Ft. Lauderdale to Gainesville/Ocala area, about 325 miles.

Drove it home, about 325 miles, much of that at over 90 mph, all of it over 75 mph. Confirmed today that the upper hose stays as soft as when cold, even when well heated up and run for quite a while. There is no pressure in the coolant tank.

There is NO coolant consumption, no evidence of coolant on the spark plugs (they are, in fact, the closest to textbook perfect, light/medium brown, plugs I have ever pulled from a car), there is NO coolant in the oil, NO oil in the coolant, etc. NO smell of coolant when running the heater (it was cold here in Fla, so I did run it for quite a while on the way home yesterday), NO leakage from the heater control valve, NO seepage from the water pump weep hole (or anywhere else). There is NO white exhaust, NO white residue in the exhaust pipe, etc. The car runs perfectly.

I know: Do a compression test, and pressure test the cooling system. Will do, but in the meanwhile, what could it possibly be?

Addendum: Why do cars hate me? While pulling the plugs on this car, I accidentally broke the #1 plug wire. Then I get a phone call from my wife up in Gainesville - the Turbo stalled and started running rough, don't know if they can make it home. Why? Why both cars at once? Well, I fixed the #1 wire, and then called wife - she filled the tank and then, lo and behold, the Turbo is running perfectly, they were almost home when I called her. I really do think cars hate me.

But, the main point of this post is about not holding pressure in the GL's cooling system. And, how could it run so hard for so long if there was a serious problem in the cooling system?