Hello DaveyB,
Have a look at this short movie. (I did remove the radiator protection)
https://www.dropbox.com/s/buakf2payc...730_191916.mp4
Last week the engine ran first time after installation. After a few minutes, temperature and pressure was so high that the pressure vessel burst open, squirting a couple of liters boiling water at me. Smile off my face and severe wounds to both hands and my chest. Could have been worse though.
What we think that happened is this: When the engine turns, the fan is spinning but at a certain point the thermostat/clutch of the fan should have engaged but didn't. So temperature and pressure got far too high, resulting in the bursting.
Note that the mercedes 190, 2 liter radiator is mounted directly in front of the fan, as in the Sierra.
Eddy