BMW 3 Series Overheating

THE CHOPPER

THE CHOPPER

THE CHOPPER

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Joined
5 Oct 2006
Posts
490
Location
Manchester
I was sat in my 3 series compact (1996) today waiting fot the other half whilst she went shopping. I had the engine running whilst I sat in it for around 40 to 50 minutes, by chance I glanced at the temperatue gauge and noticed it was in the red. :o Then when I started to drive the car the temperature returned to halfway which it normally runs at. My mate said it must be because of the viscous fan which spins faster as you drive faster, therefore the fan was spinning at very low rpm's and couldn't sufficiently cool the engine. I checked the fan it was working and the car isn't losing water. Is this right or do I need to replace the fan or something else? I remember my mate replacing the fan on his e30 325i sport because it was overheating but couldn't get in touch with him to get some advice so here I am. Help me out guys
 
As long as its got all its coolant it should be fine.


My local mechanic told me that as long as the water / Antifreeze mixture AKA Coolant is held then its a sealed system and wont overheat.
 
The fan should usually cool the engine enough, but sitting still for almost an hour will make the engine temp increase quite a lot, often up to the red. I wouldnt worry too much just dont sit at idle for so long.
 
In my experience anything upwards of twenty mins sitting still with the engine running is enough to get the temp gauge into, or nearly, the red. Seriously though, why not just switch the engine off?
 
rmuir said:
In my experience anything upwards of twenty mins sitting still with the engine running is enough to get the temp gauge into, or nearly, the red. Seriously though, why not just switch the engine off?
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Good point. Ive only ever sat in a car with the engine running for about 10 mins before switching it off :p
 
rmuir said:
In my experience anything upwards of twenty mins sitting still with the engine running is enough to get the temp gauge into, or nearly, the red. Seriously though, why not just switch the engine off?
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It was cold so I had the heaters on but not on full(otherwise I would've felt the heat from the engine getting too hot) and I was listening to my stereo, I didn't want to flatten my battery and be stuck in manchester town centre. It was absolutely packed, took me half an hour to get out of the centre. :D
 
THE CHOPPER said:
It was cold so I had the heaters on but not on full(otherwise I would've felt the heat from the engine getting too hot) and I was listening to my stereo, I didn't want to flatten my battery and be stuck in manchester town centre. It was absolutely packed, took me half an hour to get out of the centre. :D
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does the other half drive? if so you have missed an opportunity to tag along for ten minutes, get bored, make a stupid suggestion for buying something then head to the pub :D

It works!
 
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I had a problem with a 323 many years ago, which needed a new fan assembly as I was told there was a design fault with some E46 fan assemblies that could cause the car to overheat, which mine did. Might be worth getting it checked out just in case. It should not matter how long your car is running at stand still as the car is designed to cool as required for as long as required, though I would not leave it running that long myself.
 
I checked my fan, whilst spinning at very low rpm's I can put my hand in it and actually stop it and spin the fan in the opposite direction. My mates discovery is exactly the same. Another mate(the one who replaced the fan on his E30 325i) says it isn't right, he said it shouldn't have that much play in it. Is there any way to check if it is broken or not other than the car overheating. I priced a fan up, they're only cheap but why fix it if it isn't broken. It could even be my head gasket but the same again, I won't fix it till it goes. Cost isn't an issue as i'll do the work myself, its just a pain in the arse :p
 
A viscous fan spins faster as the engine revs increase, to a point - after that, it slips so the fan does not overcool the engine. This is why you can stop one from turning.

In the housing of the viscous assembly bolted to the engine there is a hollow filled with small grooves, which match those of the rotor to which the fan bolts. In the gap is a silicone oil, which the viscosity of depends on velocity. The greater the velocity, the greater the viscosity of the oil.

As the difference in speed between the fan and the engine decrease (i.e. RPMs increasing) the viscosity of the oil drops, as the differential velocity is decreasing, therefore the engine turns the fan less and prevents overcooling :)

You know when a viscous fan stops working properly as you get below-average running temperature at speeds and typically, they go 'bang' and attempt to throw themselves through the bonnet, or unscrew through the radiators :D
 
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You know when a viscous fan stops working properly as you get below-average running temperature at speeds and typically, they go 'bang' and attempt to throw themselves through the bonnet, or unscrew through the radiators

ARRRRRRGGGHHHHHHHH :p
 
As said above by someone, a modern car should run indefinitely on tickover/idle and not overheat, even in summer nevermind winter. The temp guage will rise, but it shouldnt go into the red.
 
Well I've been out on a decent run today, on the motorway for a bit of a distance and the car hasn't skipped a beat. Parked up outside mcdonalds for a while with the engine running while I ate my food and temperature was fine. I'm just going to leave it for now as it seems fine. If it breaks I'll fix it.....touch wood that it doesn't :p
 
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