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Discussion Starter #1
Hi Guys....I have a problem with a grinding noise on my BMW 318i touring. It happens when the engine is hot and at about 2k revs.
I took it to a garage and I was told this...." the water pump runs on a pulley off the auxiliary belt ( on the front of the engine ) the bearing on that drive is causing the noise and according to BMW they sell it as a complete unit with the water pump.
So with that advice I took it to another garage, explained the issue.
They called me the next day to say the water pump is fine. I explained that I think it's the bearing (as above) and I was told that there is no bearing and the water pump is situated at the back of the engine off the Cam?
Please can someone explain to me who is right and who is wrong here.
I'm picking the car up at 11 today and I want to go in and sound like I know what I'm talking about. Being a female I hate the fact mechanics assume I know nothing. I've only had the car a matter of weeks.
Thanks in advance.
 

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Your profile says you have a 2007 318i, so you most likely have the N46 engine which has a belt driven water pump on the front of the engine. This is a complete unit as explained to you above.

There is a very slim chance that you have a N43 engine which has en electrically driven water pump, again on the front of the engine. I can't think of a BMW engine that uses a cam driven pump.

If your car is from a year other than 2007 this information might not be correct!
 

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Discussion Starter #3
Hiya, thanks for your reply.
So what the heck did he find at the back of the engine. He said he took the water pump off and it looked ok.
Is it driven at the front of the engine but the pump is at the back of the engine?
 

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There is a vacuum pump at the rear of the engine, driven off the cam.

I couldn't say if it's likely to be the cause, but it's entirely plausible.
 

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Discussion Starter #5
Thanks.
I really think it's the bearing, but I just got dismissed. It's so frustrating. He is my usual mechanic and does me good deals but I will just have to take it back to the mechanic who said it was the bearing.
 

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Discussion Starter #6
ok, so i went to get the car.

I said to mechanic i reckon its the bearing in the water pump drive and asked what the 5 (it may have been 6) pulley things were at the front of the engine, i was told it was power steering etc etc. I asked if any of those pulleys are to do with the water pump, and i was told no.

So I'm confused, both the poster above and the first mechanic i took the car to tell me it is situated at the front of the engine and this garage tell me no.

I hate being fobbed off.

I asked about the noise and the mechanic rev'd the f out of the engine and said " i cant hear a noise"

I got in the car and took it to about 1,700 revs and there it was. He couldn't hear it, so another bloke came over and said "ahh yeah, like a grinding" Bingo! "yeah probably the power steering belt i wouldn't worry about it."

But the thing is, i do worry.

There is a noise, that imo shouldn't be there and i would just like to get to the bottom of it.
 

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I dunno if you're being fobbed off or if they're genuinely ignorant of the fault.

The way the N46 engine works is that the power steering pump is attached to a pulley driven off the belt on the front of the engine, this is standard. The water pump attaches to the back of the power steering pump and shares its drive. Looking at the front of the engine you will see the belt driving the alternator, air-con compressor and power steering pump, it's not immediately obvious that the water pump is on the same shaft as the power steering pump.

You can read about the setup on this page if you'd like to be better informed.
 
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