M radiator fan not kicking in

S

samZ4M

Active member
 Oxford
Driving to work today I noticed that my coolant was getting rather hot, I even got a yellow warning. It was fine at 70 on the A roads, but coming into the city it was slow, so got hot.

Pulling over and checking, it seems the fan is not kicking in. My Intravee was saying 110degrees, so it should definitely be on! I let the car cool and put the heating on, which enabled me to get to the work car park without it getting too hot. The drive home will be clear (I hope), so should be cool enough.

So, on to fixing it! Going by the fuse layout, I figured the fan was either 33 or 57, both looked in good shape. So what's next to test? I imagine it's probably the fan that's knackered. Any thoughts?
 
Unusual to hear of an S54 overheating, personally id be careful about driving it, you really dont want to see the amber light on an S54...
Anything to do with overheating is usually a ticking time bomb, the last thing you'd want is to damage the engine or cook a headgasket, both will attract big bills!
As you mentioned my first port of call would be check coolant level/mix, fan/AC function(use the same fan) or thermostat :)
 
Sounds like your fan is dead. They are pricey items, but easy to replace. The good news your temp gauge is doing exactly what it is there for. Warning you before the engine is too hot. Keep a very careful eye on the temp gauge and get it changed as soon as possible. Mine failed on a scorching hot day in the middle of Bath, ie miles from home. I had the amber lamp on twice, before I was able to get home and change it, both times were in traffic and both times I pulled over and waited for the temp t drop. As above if you don't have to then don't drive it, to be on the safe side. Mine was absolutely fine by the way, like I say, that is what the amber warning lamp is there for. :wink:
 
Fan pack is common..

My roady had to have one years ago... Mad money from BMW,think there over £500,but breaker parts are available,

IIRC they are identical on 3.0si...
 
I drove the car home and it didn't come on, got up to 99 on the Intravee system in light traffic, but doing 60 it was at about 80, obviously I keeping a close eye on it, ready to pull over.

Car won't be used now until it's sorted.

Is it worth trying this fan stat, as it's a cheap part or not likely to be this bit?
 
If you get a decent indy with decent diag kit,then the fan can be activated through the diag machine.

If it doesnt work,the wiring and connection needs to be checked..Then you have a definite diagnosis
 
There is a great one 20 miles away... Don't really want to risk it. I'll think about it for a bit. Just seen that a new fan is £550 on ebay. Just as my INSP I is due, great!

Edit: Local breakers has a Z4M with no front end damage, have asked for a price.
 
I got the (assumed working) rad from the breakers. The car was working and was rear ended, no reason the fan should not work. My car has plently of coolant.

I have run my rad without the sensor connected, I’ve read this causes it to go on max speed. It did not.

I have run the new rad with and without the sensor connected and it did not come on either time.

It got to ~80, then dropped down to 78 and the bottom hose got warm, so can assume the pump works.


Car water got up to 90 when tested, before I turned it off.

Seems electrical. My code reader is not working, so will have to borrow a mates next week.

Only thing I’ve noticed is the thin cable that is the fan connector is a little green like it’s gone rusty. The main 2 are fine. I am assuming the thin cable is the ‘switch’, maybe the cause?

Any other thoughts?

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Thats got fretting corrosion..Its the modified signal wire that tells the fan to activate

Will be rotten inside,you have found your fault just need to repair that wire now
 
Humm. seems there is enough slack to trim it and re-crimp, at least for now to test it fixes the issue. I'll give it ago Monday.

I'm struggling to find the parts on RealOEM, there are similar but not it 100%. I suppose the crimp is going to be fairly standard, if I can't reuse it. I don't need a whole new plastic connector.
 
You can disemble it,so the pin pulls out of the connector and gives you room to let in a new wire properly.
 
Well I got it out, but managed to break it in the process. It also is pressed and I can’t get the retainer open. Best bet is to buy some new ones. But the wire in the cable had snapped, so fingers crossed this is the fix!
 
Looks like part #5 on this diagram... I'll have to measure thge gauge of the cable to get the right size.

https://www.realoem.com/bmw/enUS/showparts?id=BT93-USA-09-2005-E85-BMW-Z4_M32&diagId=61_2292

92E1B135-4EE9-4A9E-B282-492AA12DD41E.jpeg
 
Bmw generally do all wiring and plug repair kits

You could always take it into your local dealers and they will match it up
 
It’s 25 miles and generally busy the last few, don’t want to risk it. I’ll take the connector in and they can match it up.
 
The part was correct, chopped the cable back and refitted. Tested quickly with sensor disconnected and the AC on and the fan comes on straight away.

Put the sensor back on, got it up to temp and the fan kicked in at 91C, then the coolant slowly went down in temp. Going to go for a drive now, get it nice and warm then just stop and let it idle, see what happens.

Seems like it was that cable, which is a result and the parts for less than £1 to fix!
 
It’s a common fault on Z4s. Cost me a lot to fix mine, including a 2nd hand fan.
I had it at two renowned independent garages and I ended up doing the crimp fix for less than £1 myself.

Glad you fixed it.
 
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