In Reply to: Re: Metal water pump versus plastic posted by Jone T. on December 12, 2000 at 10:38:03:
I do not believe it is possible to tell unless you actually pull the pump. I just did the job this past weekend and it is a piece of cake. I did a full coolant flush, changed the water pump, the t-stat, and my belts (they were off anyway). Including bleeding and clean-up, under 2 hours start to finish. I had my car for over a week and only drove it 50 miles because I was scared of the H2O pump. It will give you the piece of mind for the next 100K or so. If it breaks on you, you can quickly overheat your engine and warp your head which is $$$$. You can get a pump for $95 or so from a stealer or from Steve D' for about $50 I believe. Easy job, if you have any questions, please let me know.
BMW originally used the "plastic" water pumps in the M50. The only plastic part is the impellor(sp?). What happens is the plastic degrades over time and then starts to break. Also under high heat conditions, it does not fair as well as metal. When the plastic breaks the plastic bits go into the cooling system and block it up.
The "metal" water pump has a metal impellor(sp?). This allows it to last longer and also does not degrade like the plastic ones. Personally if I owned an M50 or any BMW with a plastic water pump, that would be the first thing that I would change, no matter what.
Hope this helps
M535i SIG Technical Advisor
Is it possible to determine which pump one have without removing it completely from the engine, and if not, are there any pitfalls to this job?