Cooling system checklist

[duckhunt]

Hey all, after my long euro trip I started the car after a lunch the other day and a loud screeching was on with the engine running. Stopped and started again, no instant noise but it's now developed a
Bit of a screeching whine, it's quite subtle and is matched with the revs. A bit concerned of course. Nothing looks untoward on visual inspection.
I haven't driven the car since. I have taken the belts to be the most likely candidate, so I'm doing some work and have a list of bits I'm replacing. So two questions, 1.what could the noise be? 2.should I do any other bits while im doing this :

Fan coupler/clutch
Water pump
Thermostat & housing
Idler pulleys
5050 de ionised water & bmw Coolant
2 new contitech belts

Ill give it all a good clean and hopefully this will fix it.

Thanks for any input.

 

[Dino D]

Do you have an aircon? Is worth checking the additional aircon fan function properly (it's on the front of the radiator and should work in it high and low speed).

 

[duckhunt]

Do you have an aircon? Is worth checking the additional aircon fan function properly (it's on the front of the radiator and should work in it high and low speed).

Ok, so when should it be on? I stopped the car with the engine running to have a look on the way and it wasn't moving. I wasn't sure if it moves with airflow when the car is in motion or what..? Cheers. Yea I have aircon

 

[mwpe]

The aircon fan should run with the aircon switched on but if it is not running that is not the problem I would take the viscous fan off and run it for a short time and see if it is there. The other suspect is the tensioner. You could also take the drive belt off and check for any play in the water pump. All these are easy to change but the water pump is the worst as it means a coolant change as well.

 

[Dino D]

The aircon fan has two modes:
1. Low speed (may come on in traffic)
2. High speed - it always runs at high speed when the aircon is on. It can also use the high speed if needed to cool the radiator.

I run with out a viscous fan altogether and have only heard the fan come at low speed so far.

To see if it working on low speed do as mwpe says and run the engine with out the viscous attached. If the engine is already warm the aircon fan should kick in and out after a few minutes of idling.
I think with viscous on place the viscous may take over most times so the aircon fan low speed mode doesn't get used unless sat on a really day after a run.

When running both viscous and the electric fan it acts a back up I guess - it may kick in at idle so the vicious doesn't have to I suppose.

Some early 2.8's had been wired incorrect from the factory causing it to never run at low speed (mine was like this). If it was wired correctly it would kicked when my viscous fan failed...twice..that's another story (ive have had genuine viscous ones fail after a year or two so I binned them altogether now)

Hence I mention checking it.

The rest of your list is good.

I guess you could change the expansion tank - OEM manufacturer ones like from Behr are around £25 on eBay and you will be able to see the coolant level again (I have been meaning to this).

 

[duckhunt]

Ok thanks for all the information, I have all those parts ready or on order, so it'll probably order an expansion tank too.

Do you think the aircon fan could be the noise? I seriously hope it goes away after all this work, as I don't want to drive it until it's fixed, it doesn't sound very good. I'll be able to get on with the work in a week or so so I'll let you know the results. Then I can fit my new exhaust and m50 manifold

 

[Dino D]

You can unplug the aircon fan to rule it out.
You can also spin it by hand, should be quite - it's just a bi electric motor.