Bad water pump?

Hello, I'm visiting from the 5 Series forum to get your opinions too...

Yesterday my '08 535 overheated (40k mi). First I noticed that there was no heat through air vents, then the radiator fan turned on very high, then the overheat.

I've read a bunch about replacing the thermostat and water pump together, but I'm just trying to diagnose whether the pump is bad and I need to spend the $400 on that part.

I initiated the water pump bleed procedure, and the pump turns on and circulates some coolant, but it sounds very weak to me.

Please take a listen/look at my video and let me know if you think if the pump is working properly.




Thanks

take it to BMW have them replace it.

If your cars over the 4 years by how much?

Doesn't sound good to me. I would definitely replace it (will have to eventually anyway). There is a separate valve control that sends the water to the heater core when heater is switched on but if it is not getting hot then the water pump is probably not circulating properly. Thermostats rarely go bad unless they are very old but you can replace it at the same time to kill two birds just in case. Fortunately these waterpumps are easier to replace than most but are costly due to being electric. If your fan is cranking on to high speed the computer is sensing a need to cool quickly which typically means engine is too hot and poor circulation. 40K Miles is pretty low for a bad pump though. You are under warranty so just take it in!

Thanks for the recommendations. Unfortunately I'm not still under warranty (expired), but this job doesn't look like it's too hard to do.

Call me a luddite, but it's irritating that something like a water pump needs to be electronic. Then it fails without warning, (and there's no temp gauge to monitor the system) and costs 4x as much as it should. Why, all to save a couple MPG?

Originally Posted by maggasp

Call me a luddite, but it's irritating that something like a water pump needs to be electronic. Then it fails without warning, (and there's no temp gauge to monitor the system) and costs 4x as much as it should. Why, all to save a couple MPG?

Electric water pump is actually a good idea, as it allows variable coolant flow (low for faster warm-up and low emissions and high when driving aggressively).

It also makes possible to circulate coolant after engine shutdown to cool down turbochargers in 335.

Bleeding cooling system after replacing coolant is also easier and is done without starting the engine.

But yes, it is expensive compared to belt driven pumps...

In My Mercedes I had to replace the waterpump twice. I got it down to 2 hours but first time took me 6! And...I had to take almost the entire front end off. Also this was a 1991 model. The waterpump still runs aftermarket, $170.00, online. Then, I had to park it on a steep incline with the nose up and bleed the system to get all of the air out. So not sure the electric pump is such a tough job or bad idea in comparison. I actually like the electronic waterpump and my understanding is the car will shut down before it overheats and blows a head gasket (which is what happened the first time my waterpump went out and I eventually had to replace that...Multiple ALL DAY JOB!!!). I wouldn't want to have to replace a head gasket on this baby.

Thank government regulations. Either they do stupid stuff like this to get the mileage up, or we all drive underpowered, uninteresting shoe boxes...

Most failures I have read about are related to guess what, poor electronics in the pump itself. BMW seems to have a long standing issue with issues related to this in all their models. Seems like if they would beef up that issue by making their suppliers meet higher reliability standards we would all benefit.
I am probably not far away from needing to replace mine and I am actually looking to buy one if I can source a good price and keep it in the car just in case.
Oh well goes with owning a car like ours. If you think about it an electric water pump is a much better idea so it can run hard in stop and go traffic and easy on the interstate. Good idea but implementation related to electrical reliability needs some work...