Hi guys,

Mechanic replaced timing chain guides, chain, water pump with metal impeller and friction wheel on my 2011 Clubman S. Discovered that guides were breaking, so caught it on time (132K miles).
Problem is - right after all this work was done, there is knocking noise on cold start. Found it that when friction wheel is not engaged (water pump is not running) it makes that scary knocking noise. Replaced it again - same noise, third time - still makes noise on cold start, goes away as soon as water pump is engaged.
Any ideas why does it do that?
Thank you!

 

I guess I’m not understanding the “engaged” part of the water pump. Shouldn’t your water pump always be engaged with the friction wheel after disengaging the release tab? Sorry if I’m not understanding your question.

 

when engine is cold, water pump is disengaged, to warm up faster and that's when it makes that knocking noise. If I pull that service tab, no noise.

 

Ok, I guess my engine is different. It has a water pump driven by a constant connection between the friction wheel and water pump pulley. Coolant flow is regulated by the ECU controlled thermostat housing. Knocking noises in the area are usually a breakdown of the friction material on the water pump pulley on my setup.

 

Water pump pulley and belt are new, really stumped.

 

There is a contradiction in your posts. This:

contradicts this:

Pulling the service tab dis-engages the water pump. From my understanding, a knocking noise cannot be produced by the friction wheel (or from the entire assembly driving the water pump) when the friction wheel is not engaged.

FWIW: in my car, residue of melt belt rubber inside the tracks of the crank pulley caused a knocking noise when the pump was engaged (and a rattling noise made by the vibrating friction wheel when the pump was not engaged). If you want to compare the knocking noise with your car, listen between 1:10 and 1:20 in this video of my car:

 

(Some?) american models have the water pump constantly running. European models all have an ECU controlled friction wheel assembly (in addition to the ECU controlled thermostat).

Knocking noises can also be caused by a worn serpentine belt.

 

Well I guess my R56 with a very European N18 engine has a mechanical friction wheel with a constantly running water pump. Had everything off when I did my timing chain and no wires connected to the friction wheel. Do you do your own maintenance on your car or go by the words of a mechanic?

 

Was your R56 made in order to be sold in a european country?

Of course all R56 (and the engines inside of them) are made in Europe. I was referring to cars made for the american market (according to US regulations) vs. cars made for the european market.

 

To clarify - on cold start, there is knocking noise, if I pull service tab while it's knocking, noise goes away ... engine running very quietly and there is no noise if engine is warm. Replaced friction wheel 3! times. Belt is new, water pump and its pulley are new. Planning to take it back to mechanics and let them deal with it, engine was running very quietly before timing chain guides, along with water pump were replaced.

 

So the knocking noise is there when the waterpump is driven.

The fact, that there is no noise when the engine is warm points to the water pump itself (assuming that all pulleys are attached properly).

 

I thought that water pump is disengaged on cold start, to warm up the engine faster? And at this point friction wheel is "loose" and making noise. And it's quiet when it's actually driving water pump. I could be wrong, but I thought the whole purpose of friction wheel is to control water pump, engage it(drive it) only when needed.

 

As mentioned above: R56 made for the US may (or always do?) come with a permanently engaged friction wheel. If your car was made for the US market, the water pump will be driven at all times, including at cold starts.

If that were the case, how would pulling the service tab make the noise go away?
Note: pulling the service tab always leads to a disengaged friction wheel (whether it was previously already disengaged, engaged due to the ECU telling it to be engaged or engaged due to it being engaged at all times).

Either this is true, or this: "If I pull that service tab, no noise." Both cannot be the case. Which one is it?

See above (country specification)

 

R56's made for USA all have water pumps driven by the friction wheel. They are not ECU controlled. Pulling the friction wheel service tab will dis-engage the wheel and stop the pump from turning. Pretty obvious to me, based on the above descriptions, that the new water pump is defective or installed wrong. I suggest that GrneEyeDog find a copy of the Bentley manual and learn about his car. Maybe bookmark this illustrated parts list too --- https://www.realoem.com/bmw/enUS/select

 

I really appreciate all your help, thank you! One thing I do not understand ... say it's defective water pump or pulley on it is installed incorrectly. But why the knocking noise stops, once engine is barely warm? Wouldn't it make noise all the time?

 

Does it do this on every start up, or just cold start ups?

Could possibly be cavitation in the water pump system on start up? Has the water system been carefully bled for air etc?

 

Heat makes many materials expand. Expansion may eliminate gaps/tolerances which at lower temperatures allow parts to move instead of being afixed.

It is useless to speculate further about the noise of your engine given that we do not know what is actually happening. Judging by your contradicting descriptions so far, I wouldn't want to eliminate anything at this point (including the possibility that the noise has nothing to do with the water pump driving assembly but comes from inside the engine).

So (for my last time), please check (with your eyes, not by infering):
Is the water pump pulley turning when the knocking noise is heard?
If so: does the knoking noise stop immediately when you pull the service tab of the friction wheel?

 

Issue solved: defective water pump was making this noise! Symptoms, horrible knocking noise, resembling engine rod bearing knocking on cold start, goes away after engine warms up or if tab on friction wheel is pulled. Replaced friction wheel, belt tensioner and belt, noise still there. Water pump it is.
Defective pump was brand new, Hamburg Technic, with metal impeller, makes very faint squeaky noise when out of the car and span by hand, like rubber rubs on something.

 

I have had consistently dismal experiences with both BMW and Mini aftermarket coolant pumps, they have had a high failure rate and fairly short lifespan. I no longer buy anything but OEM pumps and that is about the only OEM component I buy.