Hi guys. I rebuilt my engine in early 2014 and at that time decided to spend a bit more and use a BMW branded water pump. About 8,000 miles and 4 driving seasons later, the pump started oozing coolant from the weep holes. Enough for a few drops to reach the bottom of the engine after I stopped the car, so not a gush but a definitive leak. Car was run with a 60/40 distilled water/ Prestone green antifreeze solution, never older than 2 years.
How long have your pumps lasted? I'm going to see if my hydraulic press will press it apart to see what the innards and seal look like.
I replaced it last night with a Graf 'made in Italy'.
Maybe the secret is getting a pump bearing a "tested" sticker?
(One wonders what testing is involved, and whether that includes every pump sold.)
It should go without saying that, mass-produced water pump quality control is imperfect and a few failures are inevitable. That said, aside from avoiding rough handling, pump life can be significantly reduced by over-tensioning the drive belt. It stands to reason that a belt that is too tight will likely lead to premature wear. This holds true with alternators or any belt driven accessories. A related consideration is to ensure the driving belt path is aligned. Misaligned pulleys may be a rarity, but that condition does not lead to belt or component longevity. Finally, we all known longevity can be enhanced by regular cooling system maintenance with quality water and coolant - or at least a water pump lubricant.
I've experienced both ends of the spectrum regarding M30 water pump life. That includes a new pump installation that leaked via a weep hole - as soon as the engine reached operating temperature and the system was pressurized. That pump, to the best of my recollection, came from a dealer, and was readily exchanged for a like part. I suspect it had been sitting on the shelf for a long time. At the other extreme, I have also had pumps that seemed to last indefinitely. I use the word "seemed" because sometimes, a water pump's health is not always obvious by simply inspecting weep holes or checking the driven shaft for axial play. In one instance, normal coolant maintenance was accompanied by mission creep that included changing the original mechanical fan clutch and the pump. The pump was probably 25+ years old and there was no obvious indication of an impending problem, e.g., overheating. However, the cast impeller was so significantly corroded that I was surprised it moved any volume of liquid.
In addition to the cast solid wheel-like impeller, I have seen and occasionally used water pumps employing something similar to the impeller pictured below which appears to be stamped/bent steel formed vanes. I have no idea if it lasts longer than the cast wheel-style impeller, but I have been using one like it since Mr. Clinton was in office. Rumor has it that the stamped "star " style is not as effective as the solid wheel style due to cavitation. Nevertheless, there are many pumps using this style and I would imagine cavitation issues are probably minimized with tight tolerances between the vanes and the preformed passages of the pump and corresponding mount. My own preference would lean toward metal impellers, but I am not sure I would automatically condemn the use of plastics. I say this not having any experience with them in M30 pumps and considering the pervasive use of plastics in radiators and coolant expansion tanks and pressurized caps. Granted, plastics have a tendency to become brittle and, unlike metal, once broken, they are difficult to fix or restore and generally have to be replaced. But
maybe the newest plastics last as long as their metal counterparts?
