If your luck is anything like mine, look into getting it fixed sooner than later. A month or so ago, my slight seep which I had for years turned into a drip. Within days, my pump was sounding like yours. As a temporary fix, I tried Lucas leak stop. A few days later, the pump would lose all fluid in the 4 mile drive to work. I finally replaced the pump and suction hose on the bottom of it (soaked and swelled in fluid) in the parking lot of work.

 

I will pick up the dye today, not sure I will be able to locate the leak without ripping things apart.

If it is a leak from the pump whats the best course of action, replace it or attempt to rebuild? Pumps I see on ebay for around 100, which isnt bad.

 

I got an all makes pr2 as a replacement
Also rebuilt / revealed the old one.
You may get lucky and find the issue is a small hose leak....just takes a tiny one under pressure

 

Dust correct me if I am wrong but you would only be able to see the leak from the hose connection if you were underneath the car?

 

Usually easiest from below
Though, I had a leak in the return line and you could see it from above. It was inside the protective sheathing on the elbow

 

Mine only moaned when cold - and only once.
Don't worry about it.