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Old 06-30-2010, 08:19 AM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
For the coolant part of the question, see this thread specifically answering that (although for the USA, not Japan)...

As for the water pump brand, there are about a dozen that are sold for the BMW E39 so I agree it's confusing to choose one.

I think you (and I) have two fundamental options:
a) water pump, paper gasket, & rubber o-ring with composite impeller (OE & OEM & OES & OES Replacement)
b) water pump, paper gasket, & rubber o-ring with metal impellers (Aftermarket)

Since I have a cooling-system overhaul in my near future, I researched, & found a confusing dozen E39 suppliers:
1. Hepu (Cam likes 'em ... what more do we need to say ... )
2. Geba (heavy cast metal impeller, bearings sometimes fail)
3. Graf welded steel impeller (better but also occasional bearing failure)
4. Stewart EMP (some say they beef up the bearings to handle the metal)
5. GMB (I think this is OE with composite plastic impellers???)
6. Hella (I think this is OEM with composite plastic impellers)
7. Bosch (I don't know of any users who reported back on these)
8. Beck Arnley (they sell 'em but I don't know anyone using them)
9. Airtex (again, they sell 'em, but we'd have to hear from users first)
10. AC Delco (same as the last two above, they sell 'em)
11. A1 Cardone (they sell 'em, don't know much about 'em)
12. ??? please correct this list as needed so we all benefit ???

On the topic of the housing for the thermostat, I echo the sentiment that I've read the aluminum sometimes leaks due to a poor casting; yet, on the other side, the plastic is weak after 80K miles ... so ... it seems to be a tossup as to which way to go.

Do we have any KNOWN good brands for the aluminum thermostat housings?
(Note: I opened a separate water-pump supplier pro/con question over here.)

Last edited by bluebee; 06-30-2010 at 09:13 AM.
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