[F30RiK]

(English is my third languages so please if I do mistakes in sentences, Im still trying my best )

My water pump broke last month on my 2006 330I at 180 000km (111 000 miles).

Yesterday I decided to open the old one to see why it broke.

I saw on many forums that usually there's a seal inside that break and let some coolant on the circuit board (That wasn't the case for me)

I first tried to turn the impeller by hand, it didn't seems to be stuck, it was spinning freely.

Then I disconnected the circuit board from the motor, hooked up 12V directly on the motor, and the motor was making EXACTLY the same noise that when the pump was on the car, a clicking noise every 5-10 seconds.

The culprit was the motor.. NO EVIDENCE at all of water on the circuit board, all the seals were in PERFECT shape. Circuit board looked like new.

I still dont understand why this parts is so expensive because basicly, there's nothing inside, a motor, a circuit board, that it.

Here's the pictures ;

[3s4u2]

Thank you for sharing the pictures! Always wondered what they looked like disassembled.

[Welcome to NBA Jam]

Huh. A lot simpler than I thought. I assume the capacitor is what allows the pump to run when the car is initially turned off. That way it won't drain the battery. Cool!

[bimmette]

Interesting! Thanks for sharing!

[unrealii]

Thanks for the pictures. Very cool to see what's inside

Originally Posted by Welcome to NBA Jam

Huh. A lot simpler than I thought. I assume the capacitor is what allows the pump to run when the car is initially turned off. That way it won't drain the battery. Cool!

I'm pretty sure it pulls current from the battery to run when the car is off.

[galahad05]

Originally Posted by unrealii

Thanks for the pictures. Very cool to see what's inside




I'm pretty sure it pulls current from the battery to run when the car is off.

Exactly so.

The Honkin' Big Cap (tm) is there to supply enormous surge currents when the thing starts up. Think of it as a local power reservoir for instant demand.

[tturbolife]

So which part of these fail?

[PhaseP]

From pictures that doesn't look like a regular DC motor that would work without the electronics. It looks like a brushless motor and would work only with the electronics providing alternating currents in those windings appropriately.

I don't think you can test it without its circuitry.

The cap also looks to be part of the driving circuitry, along with the inductor there, making switching supply voltage.

[Welcome to NBA Jam]

Originally Posted by galahad05

Exactly so.

The Honkin' Big Cap (tm) is there to supply enormous surge currents when the thing starts up. Think of it as a local power reservoir for instant demand.

Ah makes sense. Thank you, I learned something new today

[Gizm0]

Is the impeller made out of plastic or some kind of metal?

[kiel_dafo_kenyg_as]

It's an electrolytic cap. They dry out over time and short. Maybe changing the cap will make the pump go pumping again.

[wilbur_the_goose]

Rikrikrik By the way, your English is great! 100x better than my French, and I took French for 3 years!

[Larsim]

Wow, I too thought this was a simple part. BMW's markup on these things must be 1,000%.

[3s4u2]

Originally Posted by whiteblue

It's an electrolytic cap. They dry out over time and short. Maybe changing the cap will make the pump go pumping again.

I think you're on to something, such an easy fix once you get the Capacitor. I feel a rebuild project is coming-up!

[F30RiK]

Originally Posted by Gizm0

Is the impeller made out of plastic or some kind of metal?

Plastic

[F30RiK]

Originally Posted by wilbur_the_goose

Rikrikrik By the way, your English is great! 100x better than my French, and I took French for 3 years!

Thanks

[F30RiK]

Originally Posted by 3s4u2

I think you're on to something, such an easy fix once you get the Capacitor. I feel a rebuild project is coming-up!

I did it the wrong way, but there's a cover on the electronic side of the pump with 2 very small torx screws, if you take it off, you'll be able to replace the cap in about 10 minutes.

The pump is now gone in the garbage truck

[PichaDis11]

I replaced my water pump retroactively when my thermostat died. I'd love to open it up test the circuits and compare it with that of of a dead unit and see.

The hope here is to pin point what part of the pump actually fails.

Your English is fine OP. Great post by the way.

[3s4u2]

Originally Posted by Rikrikrik

I did it the wrong way, but there's a cover on the electronic side of the pump with 2 very small torx screws, if you take it off, you'll be able to replace the cap in about 10 minutes.

The pump is now gone in the garbage truck

Thanks for the info...