Water pump. Plastic vs Metal impeller?

[fernando306]

Hello my friends,

I'm a bit shocked but not surprised that the impeller on the OEM water pump is plastic.
With that said, I'm replacing my pump, as my car just crossed 100k.

Should I buy the replacement with a plastic, or a metal impeller?

I've found comments that the metal impeller can break at high RPM and cause damage. The plastic impeller is weaker, but safer? No idea. What do you recommend?

[enuff_zed]

Is the pump you're replacing the original?
If so then I'd suggest you're pretty safe to fit another plastic one.

[patriot66]

From what I can gather some metal impellers seem to be assembled from several parts and spot welded together, which over time must corrode and fail

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Four years ago now I fitted a new Meyle pump with metal impeller which is ALL cast components throughout with quality seals and bearings and a 2 year warranty....still going strong

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[fernando306]

Ohhhhh hohohoh MAJOR difference.
Looks like the metal impeller is a death sentence, but the CAST aluminum one is the way to go.

I wasn't aware there is such thing as a cast aluminum impeller. Thank you guys, that's the pump I'm buying for sure.

[patriot66]

The original pump on mine had a black plastic impeller but it was the bearings that failed and leaked. Can't see any reason really why an aluminium impeller would be better than plastic but I like Meyle components quality, fit and finish and they also usually have a 2 year warranty. More than happy with mine

[smorris_12]

This probably goes back to when BMW first introduced plastic impellers in the 90s. They were troublesome and tended to come loose on the shaft. BMW later went back to metal (presumably cast) impellers for a while until they sorted out how to do plastic reliably. Aftermarket ones tended to then be metal from there onwards as there was much crowing about plastic bad, metal good and this is long incorrectly repeated in forum lore.

I'd have a "plastic" one any day for the lower rotational inertia.

[Mike6]

And dont forget plastic is lighter than metal so extra performance - every little bit helps.

[Smartbear]

This probably goes back to when BMW first introduced plastic impellers in the 90s. They were troublesome and tended to come loose on the shaft. BMW later went back to metal (presumably cast) impellers for a while until they sorted out how to do plastic reliably. Aftermarket ones tended to then be metal from there onwards as there was much crowing about plastic bad, metal good and this is long incorrectly repeated in forum lore.

I'd have a "plastic" one any day for the lower rotational inertia.

The water pump on n52 engines has no parasitic drain on the engine as it’s electronic
Rob

[Rockhopper]

Still a parasitic drain as the electricity has to be generated somehow.

[Smartbear]

Still a parasitic drain as the electricity has to be generated somehow.

On an e89 that’s done under braking, so no parasitic drain
Rob

[dtrandall]

my understanding is this…

the first water pump had a plastic impeller which over time would get brittle and break.

Revision 2 swapped a metal impeller for the plastic one but the extra weight stressed the bearing which would fail prematurely.

Version 3, the “ it’s fixed now…really” version used a new composite plastic impeller that supposedly doesn’t break….but who knows.

there are after market sturdier all metal pumps but they’re 3X the price…and will outlive the car. but there is still the plastic radiator, expansion tank, thermostat housing, etc.

[Paul_RK]

Only OEM or SaleriSil with WPS impeller!