I thought the coolant pump on my MXR sounded a bit funny when first turning on the key, like it was running dry for a second before the sound of it smoothed out. I took off the cap and couldn't quite see the coolant in the hose, so I topped it up with only a couple ounces until it was visible. Now, when I turn on the key, the pump sound is consistent. Worth taking a look if yours sounds a little off!