Water pump impellers. Metal vs. plastic

[DR.ZED]

Ran across this. Interesting.....

http://www.blauparts.com/audi_water_...ntroversy.html

Click the video.

[5style]

bullshit. Metal > Plastic shit, end of story

[Axxe]

To be honest, I wasnt impressed with the impeller design on the metal impeller pump I put in my car. The plastic unit I replaced had a significantly smoother profile and what appeared to be a higher efficiency design. But everyone runs the metal units without issue, not so much with the plastic unit. I just dont trust plastic components in my cooling system, the only plastic I have left is the HVAC system.

[Steve30]

the only metal impeller pump you should go with is the stewart.

[Axxe]

Next time

[SiR]

quality varies with some of the metal replacement pumps(some of them bad)...but still better than the composite ones.

[rdc]

They have the same debate over at the Porsche Boxster forums. There's reports of the plastic water pumps impellers disintegrating and bits of the impeller getting lodged in the cooling system. There's also reports of metal impeller water pumps failing and the metal impeller grinding away at the aluminum engine block. I guess you through the dice and take your chances. As for me I just replaced mine with a BMW water pump. Maranello discounted of course

[ScotcH]

Yup, we've seen the el'cheapo metal ones fail. The ones that look like they're made of tim foil and soldered togther are shit. The cast metal ones are good. The Stewart racing one is the best. The new ones from BMW are supposed to be made of different composite, and are lass prone to failure ... don't have any 1st hand experience though.

[DIY]

plastic doesn't corrode ... but will if your system isnt bled properly, if there is any air in the lines it will corrode anything in time... however if were talking about structural failure I guess metal will hold up better to the heat... But I havent had to change mine yet so I havent had a chance to see

[Blackedout95]

Metal everyday, replaced many plastic one's, none metal yet due to breaking apart like the plastic. The plastic will break, just a matter of time.

However while some models get metal now from the dealer that originally came with plastic, many newer models still have plastic, go figure.

[SiR]

the composites have come a long way but they are still a cost cutting measure...something the video forgets to mention. derp the engineers tested it all and the brightest minds chose composite...errr thats not exactly how manufacturing works.

$$$ has a very important role in the decision making process.

[Dinanstu]

Improved bearings, better flow, better construction and better quality SS impeller is the Stewart water pump....

There is more to pump dynamics than the impeller, having said that - you won't find many plastic impellers in industrial applications.

[Maple]

Plastic/composite all the way.

You can not beat lightweight and technology advancement, hell even oil pans are now plastic . Its all because of the fact that plastic technology advances and Im very glad it does.

Cast metal WP are too heavy for the bearings and the bearing will eventually give out, much sooner then a plastic impeller will ever break. Before I put a Stewart in my car , my original plastic water pump had over 150k kms on it and still worked fine, on my other BMWs the plastic water pump impellers lasted 160 and 145 k kms. Good enough for me

[Dinanstu]

Originally Posted by Maple

Plastic/composite all the way.

You can not beat lightweight and technology advancement, hell even oil pans are now plastic . Its all because of the fact that plastic technology advances and Im very glad it does.

Cast metal WP are too heavy for the bearings and the bearing will eventually give out, much sooner then a plastic impeller will ever break. Before I put a Stewart in my car , my original plastic water pump had over 150k kms on it and still worked fine, on my other BMWs the plastic water pump impellers lasted 160 and 145 k kms. Good enough for me

This is the most ridiculous thing I have ever heard.

...I think we'll change all our pumps to plastic impellers at work here, so to take the load off the bearings and save money....I mean what do engineers know about roatational and vertical forces and heat on bearings?
...Good luck with your plastic, high tech impeller...

[SiR]

your car has all kinds of bearings that have to deal with a lot more weight/force....

sure bearings wear out but plastic fails a lot more than the bearing wears out.