Originally Posted by long-gone

It is my understanding that the M103s & M104s take the high temperatures very well, even up close to or even briefly into the red without too much worry about engine damage. I'm not recommending it of course, but that's what I've heard more than a few times.
As far as the coolant, it sounds like you had barely enough in the block to get the thermostat to open up. When you refill the system after emptying it (particularly if you use the block drain) you're supposed to open one of the cooling system bleed plugs (located on top, front of the head along side the valve cover on the intake side) and fill until coolant comes out of it. Likewise, if you have a bleed plug on top of the thermostat housing, you should open that too, which will help you make sure that everything on the radiator side of the thermostat gets filled properly. make sure you have the heater on high so that coolant fills those portions of your cooling system.
Even after observing those steps you'll still probably have to add a little to top it off after a few drives.
The noise you heard was probably just steam whistling through the system, I doubt you hurt the water pump.

On a side note, getting all the oil residue out of the system after a head gasket failure can be very difficult. It took me about a month to get it all (almost all) out of mine. I drove my M103 for nearly a year with a blown gasket and it got pretty saturated with oil even though I siphoned it out of the coolant tank almost daily. After the new gasket I flushed it 3 times with Dawn dish detergent, with Shout laundry detergent and finally with MB citric acid flush. There was still so much sludge getting into my coolant tank that I was beginning to think it was still leaking. I was avoiding putting in my new radiator, hoses and coolant tank until it got cleaned out. But what I began to realize was that my old radiator & tank were just kind of recirculating the sludge that was finding it's way (floating) to the high points of the system (the top hose, top of the radiator and the coolant tank). The sludge also tends to coat the walls of the system after a while rather than float. So I ran it with just water for a few weeks, cleaning what I could out of the tank each day and letting all the sludge find its way to the top of the system, then I replaced the top hose (old one was just filled with goo, the radiator too), put in a new radiator, and coolant tank and flushed it once more with Prestone flush. After several days, no signs of any sludge, just a light film that should clean out with one last flush before I put in the final antifreeze solution.