I'm planning to have my serpentine belt replaced, and while in there also replace the water pump and thermostat. I've heard various pumps are offered or have been used with this engine - metal impeller, plastic impeller, after-market ball bearing "upgrade", etc. Does anyone have experience with which pump is best? I think my mechanic recommends the BMW factory pump with the plastic impeller (he's a factory parts kind of guy). But I'm always looking to upgrade while I'm in there - if it's really an upgrade.
I have heard from Mike Miller of Roundel's Tech Talk that the Stewart water pump is THE one to use. Turner Motorsport (among others) sells them. http://www.turnermotorsport.com/htm...roduct&utm_medium=feed&utm_campaign=STE 30330
Thanks for your response. Yes, I think that Stewart pump is the after-market upgrade I've heard about, but I haven't heard if it's a superior replacement for the factory pump for everyday driving or if it's perhaps a racing upgrade (perhaps higher flow, etc.). Sometimes a racing upgrade may be unsuitable for everyday driving. I'll google the Stewart pump and research.
You also might email Mike at 'techtalk@roundel.org' and he can give you the full details (he responds very quickly). One thing I have learned about Mike over 11 years or so is that he won't recommend an upgrade/component change for a particular application unless it is truly beneficial to the vehicle and its intended use.
Stewart Pump I installed a Stewart pump 18 mo's/25k miles ago as part of the normal E39 cooling system preventive maintenance. No problems so far. I plan to run it longer than I would the plastic pump.
Go with the Stewart! It is the much better quality, you can really see and feel the difference when you hold them next to each other. I used on on my E36, that is now sold. I would buy again if I had a motor it would fit in.
While doing a coolant flush last year, I replaced the stock water pump (plastic impeller) with a Stewart Racing Pump from BavAuro -- and got an immediate horsepower boost. Love it!!
Sorry to burst your bubble, but I don't think the Stuwart High Performance Pump adds any horsepower. It is mostly just a more robust and durable water pump.
