Ok, enough with the plastic water pump impelers
 

I just read another thread of plastic impellers fear.

How about we state the facts and no I'm not trying to argue but just to stop with internet rumors.

Yes, long time ago, BMW did the blunder with poor quality composite impellers and there was number of failures where impellers disintegrated.
BMW fixed this with updated style composite impellers and I'd like to hear of recent documented failure.
I replaced number of WP's with quite a bit of age on them with worn bearings (weeping holes) and yet to find composite impeller issues.

On the other hand, I constantly hear of talk that metal impellers are better while opposite is true: Cast metal impellers are harder to balance and are heavier which is more stress on bearing.
Also, spot welded metal impellers are often poor quality and spot welds can fail and cause impeller to break free.

When it comes to WP, I actually choose OEM WP with composite impellers or OEM equivalent such as Saleri.

No, I'm not the greatest mechanic out there and actually far from it, but sometimes all of us including me unknowingly spread false rumors.

I agree totally!! The two recent water pump failures I had were not a result of the impellers... Just the outer bearings coming apart... The impellers actually stayed together...

Additionally, the local parts store version I did purchase failed less than 30 minutes of run time... It's impellers did come apart when the bearing failed...

Cheers!!!

Good point.
I remember some time ago needing a WP the same day and going to Pep Boys.
I don't care much for them but they did have Bosch WP in stock for E39 I6 IIRC. I took it out of the box and it had big heavy cast impelers and the casting looked very rough.
On the other hand I just replaced original WP on my X5 (14 y / 109 k)
It was weeping and the bearing was starting to go but composite impellers looked good and I've actually tried to break and bend them with no success.
I used Italian made OEM Saleri with composite impellers stamped INA Germany. The gasket seemed inferior and it did leak upon installation until I went with Victor Reinz gasket with black silicone bead embedded on one WP side of gasket.

Welcome to world sourcing of auto parts and their components. Some vendors just allow their buyers to select who can build the cheapest and meet the min standards. Others build everything in house to control warranty, defect rates, and then costs. Low volume vendors always go for cheapest components/parts as that is their way into the market..."We are the cheapest!"
The great rule of DIY to follow is always use OE or the OE/OEM replacement parts, if you are planning to fix it once for life. Then again, its your efforts, time, and $$ so you get to choose the path that fits your life. In the repair world this second path is called the "Coat Hanger Method"

For the "but there are exceptions"...crowd, there are always improved parts from some vendors that are designed to resolve OE manufacturing short comings. Example Meyle HD thrust arm bushings to name one.
This forum and others do a great job pointing out what to watch for in buying parts. Thanks for bringing up Water Pump impeller misinformation/noise.:thumbup:

I have a welded impeller WP running in a E39 for now going on 8 years with no issues. I pulled it out last year for an inspection while doing other repairs and just put a new seal on it as I touched it.

I agree and glad you made this post - the OE Water pump has zero shortcomings besides time and age of component -

When it comes time to do my water pump (currently 14 years and 94k miles), I would either replace with a new or reman OE unit, or only something like the EMP Stewart which is a super high quality and basically bulletproof replacement. It would probably outlive the X5

:iagree:

My experience:
My Indy just did the valley pan/coolant pipe job.
He changed out the water pump. It had 100K miles.
Impeller was original factory install plastic.
No leaks, was in decent shape. Just a preventative maintenance item.

2004 X5 4.4

Agree that OE water pump is a good choice as long as you replace them on a normal service interval. I have always changed them out at the 100K mark and have never had a problem with the performance over the next 100K.

In the e36 days... it was mandatory to get a non-composite water pump impeller. Nowadays all those issues have been fixed to my knowledge. It has been quite some time since I had a WP's impeller fail due to the material used. I usually see/experience bearing failure instead over the last 8-10 years.

From what I have come to understand, cavitation due to low coolant level/overheated coolant is the primary issue in pump impeller failures.

https://blog.craneengineering.net/wh...ump-cavitation

https://en.wikipedia.org/wiki/Cavitation