Heater Core Woes
So today I replaced my 1985 318s faulty heater core, and while I was at it I put in a new heater valve. It was actually quite easy, at least more so than I was expecting. Now the heater does in fact work, but a VERY weird sound has started. A knocking that gets faster as the engine get higher. It is not coming from the engine compartment. It is coming from the heater core / surrounding area. I don't know what would be making this noise other than the new valve. It does not make this sound when I turn the heat all the way down to cold.
Two side notes to this. My battery is not holding a charge, or I haven't driven it enough to get it charged back up (it sat a little while). And also I removed what appears to be an axillary thermostat that was in the line between the engine block and the heater core inlet pipes in the engine compartment. I had heard this was unnecessary. Was I wrong? Was that not a thermostat? Could a low battery be causing the valve to malfunction?
So any ideas would be great, I didn't even start to try and figure it out as it got dark out and I was burned from replacing everything all day.