what normally fails in the water pump?
 

145k 2001 3.0 vehicle.

I'm going to be doing my oil filter housing gasket in the near future and really thinking of doing the water pump at the same time as I dont know if its original or not.

is it the bearings that give out or the plastic impeller that falls apart?

should I just go with an oem replacement or one with a metal impeller?

I only know of a metal impeller unit from another thread I randomly came across on here months ago and its stuck around in my head but I have no idea who makes it or how much it costs...

You should look at cooling system overhaul if it has not been done at that mileage.

Water pump failure typically starts with the bearing, on any vehicle with a belt driven water pump. As it gets looser over time (sometimes quickly...) it then takes out the seal, and starts to leak.

The impeller material is a non-issue.

BMW used plastic impellers in some models years ago. They had problems, and stopped using them. No X5 ever had a plastic impeller according to BMW techs on here. The X5 water pump uses a composite impeller, which some mistake for the old plastic one. I would have no concerns using a composite impeller pump. The pumps being promoted with metal impellers are playing on the fear of something that hasn't been an issue since the 1990s. What is important is what the pumping performance of each impeller design is. I don't believe that spec is published by BMW, at least I haven't seen it. So, if you buy other than an OE water pump from BMW you are trusting that it will function as well as the one that was designed for that vehicle, and not just physically fit in the space. That is the best reason to use an OE pump from BMW, and not just one that fits in the space.

:iagree: with JCL. I know a member who replaced with aftermarket pump and was not up to the flow characteristic of the OE pump, so he changed it out to EMP Stewart. I would do that one or OE pump

LOL. Would that be me Ricky??!?!

I went with the GEBA unit but at extreme cold temps noticed decreased flow at idle (my heat would cool off slightly). The casting edges were crap quality....maybe I got a bad unit, who knows. Slapped in a stewart pump and all has been well since. I think it also comes with a lifetime warranty if my memory serves me right.

Sorry but this is funny,

I'm in the club of if it ain't broke don't fix it. When it brakes replace it with the proper part. It may last another 145K but who really cares weather it's bearings or the impeller? No one is going to just replace bearings or an impeller. What ever goes wrong, if it stops working your gonna replace the whole thing correct?:D

:iagree:

Plastic impeller problem was in M50, S50, M52, and S52 engines, not M54 engines. Stick with OE with composite impeller. Aftermarket metal impeller is heavier than composite and can led to quicker bearing failure. Also, heavier metal impeller uses more horsepower since it requires more effort to move the heavier part.

Yes S would be the one lol!

And that is why I recommend OE pump or EMP Stewart pump, not the others for M54 and the other E53 models.

You should have told that to the one I put in my old E39 525i :nanana: :bustingup One spirited driving on a hot summer day then the car was overheated. The impeller was separated from the rest of the WP.

Impeller is a big issue in early BMWs built in the 1990s and early 2000s.
They used composite impeller to save weight (yeah, save 2 ounces out of 4500 lbs!!!).
These impellers break all the time.

The bearing, if it fails, is a result of mileage > 140K and/or seal failure, no matter what brand of water pump you are talking about.

Listen to tmv, do a cooling overhaul. Tons of info in E39 forum.

If you don't have money for cooling overhaul, then watch the coolant level once a week etc. and don't take the car on long distance trips.

Cooling overhaul is about $500-$600 in parts.

I am a person who believes "if not broken, don't fix it" but cooling system is the exception. For cooling system, I'd day "if not broken, and if you have > 140K miles, fix it before it is too late".

PS: I use HEPU Water Pump since May 2006, zero issues.