So a while back, about eight months ago I replaced my water pump on my 2005 roadster limited. I went with the Gates brand pump as I have used them before. Re-torqued per specs. The nipple on the new pump seemed a bit shorter than the one that came off and there is barely enough room for the hose to clamp on. Not long after the job the Mrs. is coming home from work and says she's got a coolant light. Get the car home and check it out, low coolant but still visible in the tank. I found coolant on the underside of the hose just before the clamp to the pump and the clamp was a bit loose, tightened it up and I'm good to go,right. Now I'm checking the coolant every day and the car is still loosing it, not much but still. I check the clamp again seems tight but I can tighten it up a bit more but I break it. Now the clamp is stock MB so I change it out for a new non MB stainless, I also replaced the hose, still leaking. So I go with a T-bar heavy duty hose clamp and it seems to be working, but, I'm still loosing coolant, the amount is less maybe about a cup a week. So I'm thinking its either the short nipple on the Gates pump or I didn't re-torque the pump right. Will have to get back in there break it down and check it out re-torque whatever, but for now its too easy to just top it off. Just wondering if anybody has seen this before. Thanks.

 

Sounds like a internal leak within the water pump. Replace it with a MB OEM pump. European motors are weird about everything which is why its recommended replacing with OEM.

 

Yea I here ya on OEM. I'm going to try a pressure test next.

 

I bought Gates water pump from Rockauto in 2015. Part number GAW 44082 CHECK YOUR PART NUMBER
It was a perfect fit and have not had any leak since installation. If it ever comes to that I will buy another Gates as I have had good luck with them over the past 50 years.