It's great to see so many Oldsmobile fans in one spot! My 73 Delta 88 Royale does not have a coolant reservoir and did not come with one from the factory (this was my wife's grandfather's car). Does anyone know if there are factory correct versions available? Without one, the top 3 inches of the radiator remains empty after it empties itself on my nice clean garage floor.

 

It's doing what it's supposed to do. Look on the side of the tank and you will see a "Fill Cold" mark. Fill it to that point and no higher. As coolant heats up, it expands. With no overflow jug to catch it, it's gonna puke right out of the pressure cap and overflow tube as you describe. You leave three inches of airspace at the top of the radiator, coolant can expand to cover the full tubesheet but not puke out the overflow.

The reservoir came only on A/C or HD cooling equipped cars and is the same p/n for 1971-73 88/98/Toronado except antilock brakes. You see the packages on ebay once in a while, and I won't swear I don't have one stashed away somewhere, from when I had my Delta ragtop.

 

Thanks rocketaider. Now I know what type of cars to look into when I travel the resting places of the retired Oldsmobiles. I'll keep searching ebay and hopefully one will pop up. If you happen to come across your stashed away unit and wouldn't mind parting with it, please let me know.