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Minifinity The Classic Mini Forum and Resource | • View topic - Overheating and no fan

Overheating and no fan

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Overheating and no fan

Postby Chunkychops » Wed 7th Aug 2013, 09:37am

My '97 MPI with front mounted rad has recently started overheating and i've just discovered the fan is not working.

I'm not sure whether the fan has ever worked atall since I bought the car about a year ago. Can you hear it when it kicks in as I can't say I've ever heard it. It has always run at normal temperature up until a couple of weeks ago when I heard the water bubbling in the header tank. Would it normally overheat in cooler weather if the fan was not working?

I drained the cooling system and flushed it out with a hose yesterday and the water was running clear and checked the thermostat which is opening and closing fine. Re-filled the system and ran the engine and it stated bubbling up again. The fan is wired to a pull apart connector to the left of the radiator although there is another smaller pull apart connector to the right of the rad which comes out from the inner wing close to the headlight which is not connected to anything.

Where is the fan normally wired to? Is there any way I can test to see if the fan works before I buy another one? I've checked the fuse and It's fine.
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Re: Overheating and no fan

Postby royallingham » Wed 7th Aug 2013, 06:00pm

Simple test - run the fan directly on the battery to see if it works. If so - then you need to look at the switching, but of course short term you can wire it through temporary switch - or leave it running all the time, although not sure how long it will last like that....... The bubbling etc may of course be more ominous...and not down to the fan..........
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Re: Overheating and no fan

Postby jedi_stud » Thu 8th Aug 2013, 09:45am

I had this exact same problem on my MPi a few years back. It wasn't until I had the engine out from a cam swap that the reason for it (frayed wiring loom that had affected the switched live to the fan) became apparent, although this might not necessarily be the reason with your car.

First thing is a relatively simple test - switch on the ignition and diconnect the plug from the temp sensor (brown plug on the thermostat housing) - this should switch the fan on as by disconnecting the sensor the ECU 'sees' that the coolant is too hot. If that works it could be that the sensor is up the duff, or that there is a short somewhere in the fan circuit. If it doesn't work, you'll need to do some further investigation.

The good news is you can put in a temporary repair (read bodge!) - the connector you are referring to in the inner wing is actually the connection for the aircon that was fitted to Jap spec minis. If you supply a 12V feed into (the live side) of that connector it will switch on the radiator fan (presumably to supply air to the aircon). Only problem is that with that arrangement your fan will always be on whenever the ignition is switched on, which can be a bit of a pain! :roll:

Might also be worth replacing your expansion tank cap as well - its only a couple of quid.
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Re: Overheating and no fan

Postby Chunkychops » Sat 10th Aug 2013, 01:16am

I have ordered a new thermostat, housing gaskets, sensor and cap. Will fit and try the fan and see what happens...

Cheers for the help.
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Re: Overheating and no fan

Postby Chunkychops » Thu 15th Aug 2013, 09:11pm

Well I fitted a new thermostat, temp sensor, expansion tank cap and re-filled with new coolant/water. Then I took the fan out and tested it, not working, ceased solid. Surprised the car has never overheated before!
Ive been running the car for a few days, just short journeys with no fan in it. The temp gauge not going past normal, but noticed a smell coming from the back end, like that familiar smell of the water when its overheating.
Then yesterday started her up and shes chucking white smoke out of the exhaust which cleared after a minute. Last night started her up again and more plumes of white smoke billowing out, but the car seems to running ok, though idling a bit weak when first started up. Any ideas?
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Re: Overheating and no fan

Postby Nozzle » Thu 15th Aug 2013, 09:44pm

White smoke = steam from your water jacket! Likely that the over heating has caused the head gasket to die with possible warping of the head. You may even be able to see bubble coming through the radiator, and possible water into the oil (mayonaise in the filler cap). Don't continue to run it! Head needs to come off and checked for flatness.

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Re: Overheating and no fan

Postby Chunkychops » Thu 5th Sep 2013, 01:37pm

Yeah it was the head gasket, luckily the head was still flat so got a new gasket fitted and now seems to be running ok.

Anyway I bought a brand new Spal radiator fan and fitted it this morning, plugged it in and started her up. Left the engine running for about 15 mins until it reached normal running temperature, but fan didn't kick in. Drove to work, still nothing. I dont think theres a fan switch, I think it runs straight off the E.C.U.
Any ideas, is the E.C.U knacked?
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Re: Overheating and no fan

Postby Chunkychops » Thu 5th Sep 2013, 01:54pm

Ive just started the car up and disconnected the temp sensor on the thermostat housing and the fan switched on. Reconnected the sensor and the fan stayed on until I turned the engine off. Started it up again and fan not working.
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Re: Overheating and no fan

Postby Brumski » Thu 5th Sep 2013, 04:23pm

Chunkychops wrote:Ive just started the car up and disconnected the temp sensor on the thermostat housing and the fan switched on. Reconnected the sensor and the fan stayed on until I turned the engine off. Started it up again and fan not working.


This implies that the wiring, relay and trigger signal from the ECU are ok and that the sensor isn't playing.
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Re: Overheating and no fan

Postby Chunkychops » Thu 5th Sep 2013, 05:09pm

I'll take it for a spin later and see if the fan kicks in atall , the temp sensor is brand new. New thermostat aswell.

Thanks for the help so far :)
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Re: Overheating and no fan

Postby Nozzle » Thu 5th Sep 2013, 10:33pm

Maybe fluid isn't getting to the sensor - is there a lot of sludge in there or poor performing water pump?

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Re: Overheating and no fan

Postby Chunkychops » Fri 6th Sep 2013, 03:57am

No sludge as far as I know, I flushed the system out. Water seems to be circulating ok.
I did about 10 miles earlier and the temp gauge sat at normal, and then just as I was parking up the fan came on so at least thats working, although could still smell hot antifreeze from the engine. Just realised I fitted 2 more spot lights a few weeks ago so ive now got 4 across the front.
Thats not helping matters is it?
How would I know if the water pump wasnt performing?
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Re: Overheating and no fan

Postby Nozzle » Fri 6th Sep 2013, 08:22am

I just recall reading in one of the mags about after market pump impellers having too-large clearance so much of the flow is bypassed and consequently poor performing - I guess this doesn't apply to factory fits though, so if you're still on your original pump this particular concern may not be valid. I guess it's all down to a visual inspection of impeller and clearances.

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Re: Overheating and no fan

Postby Chunkychops » Sun 8th Sep 2013, 12:25am

All is now good!

Did 70 mile round trip today, temperature normal and fan coming on when required.
Sailed through M.O.T this morning.

Emissions a bit high but you can't have everything :)
Thanks for all the tips.
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Re: Overheating and no fan

Postby Zippyrude » Sun 8th Sep 2013, 02:59am

Main issue cured so one less thing to worry about !
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