'97 s420 Water Pump

Car is not overheating, but I am getting air in the cooling system somehow. When accelerating from a stop, I get a "glug, glug" noise at the firewall. No leaks. I replaced the radiator cap without luck. I noticed that this noise began when my water pump started making a high pitched whistling noise during winter. The water pump noise only happened when it was very cold outside. Only lasts maybe a minute or two. Now that it is summer, doesn't do it. However, wondering if a bearing is starting to go and is allowing air into the system.

Looks like the harmonic balancer is in the way of all water pump bolts. But I don't want to remove this part unless necessay. Looks like a pain to remove the balancer, and it has to be tightened to a ridiculous torque. Has anyone here changed this part on this engine (m119) without removing the balancer? Can't seem to find a straight answer on this engine and year. Included picture of what my model's balancer looks like because I think the design changed over time.

I am aware that the workshop manual says to remove the balancer. But it apparently says this for other models and other folks have changed the water pump without removing the balancer.

Thanks,
Brian
'97 s420