General Main cooling fan always runs on max when engine is running

[nick88highline]

A few seconds after starting my Grenadier, with the B58 petrol engine, the main engine cooling fan comes on at full speed regardless of the engine temperature. It then stays on until the engine is turned off. It does not run when then engine is not running. Very occasionaly, the fan will not come on for some time, ie after the engine has warmed up.
It was looked at by an Ineos dealership (based outside Birmingham, England), but they couldn't work out what was wrong.
I cannot see how this can be normal because the fan uses a lot of power at full speed and also makes a tremendous noise!
Does anybody else have this issue?
I have heard about something called "Max Cooling Mode", but if that was set, why, very rarely, does the fan not come on?
I thought it might be the fan relay stuck on, but I cannot find that relay even after extensive research.
Thanks
Nick

 

[Tinerfeño]

Either engine or AC gets false or missing temperature sensor data and turns on max cooling. Seen this on Land Rover.

 

[landmannnn]

A few seconds after starting my Grenadier, with the B58 petrol engine, the main engine cooling fan comes on at full speed regardless of the engine temperature. It then stays on until the engine is turned off. It does not run when then engine is not running. Very occasionaly, the fan will not come on for some time, ie after the engine has warmed up.
It was looked at by an Ineos dealership (based outside Birmingham, England), but they couldn't work out what was wrong.
I cannot see how this can be normal because the fan uses a lot of power at full speed and also makes a tremendous noise!
Does anybody else have this issue?
I have heard about something called "Max Cooling Mode", but if that was set, why, very rarely, does the fan not come on?
I thought it might be the fan relay stuck on, but I cannot find that relay even after extensive research.
Thanks
Nick

Grange Solihull are worth a miss.

 

[Skydance]

As always, check the blue and black coolant is level to max on a cold engine. I suspect the blue side is low on coolant and the fan is activated.

 

[nick88highline]

Thanks for all your responses so far.
Max cooling from missing sensor, I assume, would turn up as a fault code?
I checked the black and blue coolant tanks shortly after receiving the car, and both were overfilled (measurement taken when cold) to a point where I couldn't see the level indicator. I took a lot of coolant out, around 400ml from the blue tank (yes, it was that overfilled) and have been checking since and nothing has changed, but the issue persists. I have run the coolant bleed procedure once too, but there was no change to the coolant level. I also have a non-working HVAC, which may or may not be related, blows hot almost all the time, despite trying all the tricks from this forum.

 

[Skydance]

Thanks for all your responses so far.
Max cooling from missing sensor, I assume, would turn up as a fault code?
I checked the black and blue coolant tanks shortly after receiving the car, and both were overfilled (measurement taken when cold) to a point where I couldn't see the level indicator. I took a lot of coolant out, around 400ml from the blue tank (yes, it was that overfilled) and have been checking since and nothing has changed, but the issue persists. I have run the coolant bleed procedure once too, but there was no change to the coolant level. I also have a non-working HVAC, which may or may not be related, blows hot almost all the time, despite trying all the tricks from this forum.

I suspect it is trapped air. Needs bleeding again. At least 3 times. Mine, after 3 years it’s finally working properly.

Has the dealer checked the refrigerant gas in the air con?

 

[nick88highline]

An update:
It turns out that both engine cooling fans are running at full speed all the time! I hadn't noticed that before due to the tremendous noise it all makes.
I have found the fan relay - it's under the positive charge point in the engine bay. Hard to see and access but it's there and it's working as expected, ie it switches the power on for the fan(s) a few seconds after the engine has started. Obviously being a 1000W fan, you don't want it coming on before the engine has started. The fans are controlled by PWM which is why there are acutally 4 wires going to the main cooling fan. The white wire on the fan accepts the PWM signal and this is what controls the speed of the fan. If no PWM signal is received the fan defaults to full speed. The fourth wire is to sense when the fan hits water so it can be turned off when in wading mode.
I have put the vehicle into wading mode, which should turn off the auxillary cooling fan, but it does not, which suggests to me that the PWM signal is non-existant. I have tested for the signal, but so far have found nothing.
I have bled the system again, but clearly the fan issue is nothing to do with air in the system. The HVAC system still only blows hot. Not sure if it's all linked, but maybe it is. I've yet to check the A/C charge.
The vehicle has done almost 17,000 miles and I'm not the first owner.

 

[Skydance]

An update:
It turns out that both engine cooling fans are running at full speed all the time! I hadn't noticed that before due to the tremendous noise it all makes.
I have found the fan relay - it's under the positive charge point in the engine bay. Hard to see and access but it's there and it's working as expected, ie it switches the power on for the fan(s) a few seconds after the engine has started. Obviously being a 1000W fan, you don't want it coming on before the engine has started. The fans are controlled by PWM which is why there are acutally 4 wires going to the main cooling fan. The white wire on the fan accepts the PWM signal and this is what controls the speed of the fan. If no PWM signal is received the fan defaults to full speed. The fourth wire is to sense when the fan hits water so it can be turned off when in wading mode.
I have put the vehicle into wading mode, which should turn off the auxillary cooling fan, but it does not, which suggests to me that the PWM signal is non-existant. I have tested for the signal, but so far have found nothing.
I have bled the system again, but clearly the fan issue is nothing to do with air in the system. The HVAC system still only blows hot. Not sure if it's all linked, but maybe it is. I've yet to check the A/C charge.
The vehicle has done almost 17,000 miles and I'm not the first owner.

If you done all the checks including this final one. Prop up the bonnet in service mode, on a cold engine, top up both coolant levels especially the blue one, both are level with max. On the bleeding instructions, unfortunately it’s doesn’t say check levels AFTER on a cold engine. It only says check before running the coolant procedure. BMW H12 coolant. If this doesn’t work then dealer I suggest. Trying to save you a journey.