Author Topic: Plastic Impeller Water Pumps...Anyone's Explode? (Read 2862 times)

bmwman91 · « **on:** February 06, 2008, 02:01:26 PM »

I saw that the 6 cylinder E36 cars have some big issues with the plastic impeller water pumps exploding without warning. I have replaced my water pump a few times over the years, and it USUALLY comes with some sort of metal impeller. However, the last one I ordered had a black plastic impeller.

Now I am worried. Has anyone used one and had it explode? Usually the shaft seals or bearings seem to go out before anything. Comments?

BrandC · « **Reply #1 on:** February 06, 2008, 02:10:45 PM »

Go ahead and return it. It's a waste of time and will cause headaches in the future. It was a big problem with VW VR6 engines, the fins would crack and get send flying around in the cooling tract.

Mind you the VR6 is a very hot engine naturally, the M42 has sufficient cooling and space in the engine bay. I would still personally fork over for the metal impeller pump.

haledj · « **Reply #2 on:** February 06, 2008, 02:29:54 PM »

I have never had one explode, but I would not put in a plastic one.
I helped a buddy pull out one on an m50 and it had started to crack.

hoevesruperd · « **Reply #3 on:** February 06, 2008, 02:33:31 PM »

i had to change my pump last summer. replace the previous plastic one with another plastic. the company that builds it says they improved the plastic durability since 1991 which i believe could be true. if the one i just replaced was plastic and lasted 17 years i dont see why the new one should fail anytime soon.

although if you can find a metal one go for it. i couldn't

strad · « **Reply #4 on:** February 06, 2008, 05:38:30 PM »

Yes, I blew one up on my 94 M50 on a road trip. That was fun, an experience I recommend to others :mad: My M42 had a metal one in it when I changed it two months ago -- guess that's not OEM?

bmwman91 · « **Reply #5 on:** February 06, 2008, 07:13:59 PM »

There are a ton of different M42 water pumps out there. The original one on my first car was a SUPER nice one. It was all thin aluminum sheet metal brazed together...it looked like a work of art. The replacement was some cast-iron looking impeller...not too impressive, but metal. The latest one I have is a plastic impeller model. I even paid more for it than other available ones thinking it would be metal. Poop.

The E36 M5x motor pump explosions seemed to be a fault common only to them. I would believe that the fault has been remedied by now if suppliers are allowed to make pumps and still be recommended as OE replacements. Oh well, next time I will call and make sure first.

Scany · « **Reply #6 on:** February 06, 2008, 08:02:32 PM »

The reason why BMW went from plastic to metal and back to plastic is because the first plastic ones got destroyed, the metal ones corroded because people didn't take care of their coolant and put all kinds of coolant in their engine. The last plastic one is of a stronger plastic. I put one in my E39 and I trust BMW. You should replace you waterpump every 75k anyhow, or sooner if you want to be sure you don't get stranded.