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MG MGF Technical - Fan on temp?

Where should the temp needle be on the guage when the fan (front) comes on? My fan seems to come on when the guage reads just under half way. If I have a fast drive, not stationary the fan is on when I stop. it does go off when I switch off the engine( it doesn't run on ) nor does it come on when I stop.

On another note, how easy is it to change the batteries in the remote? how long do you get once the old batteries are out?
Kevin s

>Where should the temp needle be on the guage when the fan (front) comes on?

100 deg C?

> My fan seems to come on when the guage reads just under half way.

The gauge should never move once the engine has heated up - if it is moving you have a fault.

> If I have a fast drive, not stationary the fan is on when I stop.

Strange when you add in :
> nor does it come on when I stop.

> it does go off when I switch off the engine( it doesn't run on )

There is no reason for the fan to cool the water as there is nothing causing water flow when the engine is off.
Will Munns

The gauge is not very helpful - it is so damped, that a temperature change of 5-10C is not visible as a movement. IIRC the front fan should come on when the water temp reaches 110C - but you'd need a digital readout (or more accurate calibrated analogue gauge) to know when this happens.

Second question is - are you sure you're hearing the front fan? It's inaudible from the driver's seat. The engine bay fan, however, it easily heard working, especially on a MPi after a fast run in hot weather. This fan is not triggered by water temperature, but rather by engine bay temperature.

Changing the battery in the remote is pretty simple. There is some useful info on this on Dieter's web page IIRC ( You need to separate the upper and lower halves of the casing (a screw driver will do the job, but be careful of damaging the soft plastic). The battery is a button type (similar to that used in calculators etc). It slots straight in. :o)
The plipper will then need re-synchronising with the alarm unit - 3-4 presses of the button usually does the job.

Hope this helps Kevin! :o)
Rob Bell


Many cars fans come on after the vehicle stops, the heat soak from the water is sufficient to trigger them.

Yes it is definately the front fan, I have got out of the car with ithe fan running to check

I'll do the batteries ASAp

Kevin s

>Many cars fans come on after the vehicle stops,

Many cars have an engine at the front which appreciates the cooling effect of the fan blowing air over it even if the water does not circulate. The F has a seperate fan to do this job.
Will Munns

But their fans are still triggered by the water temp in the rad rising NOT the temp of the engine. The fan switches are usually in the rad which I assume is the same on the F?
Kevin s

Nope, all newer cars (fuel injection) have the temp sensor in the water channel from the head. This is so the ECU can use the info to adapt fueling for when the engine is cold - Then the ECU makes the assumption that the thermostat must be open fully if the outlet temp is above 100, so the radiator must be hot and need cooling. So if you have no water in the radiator (HGF for ex) the fan will still run.
Will Munns

Experienced similar problem over the weekend driving back from Cormwall ... and would welcome some advice.

We got stuck in traffic for about 15 mins and temp gauge started to rise from its normal mid positon (less one mark).
It slowly moved up to within a couple of marks from the red.

I could not hear the engine bay fan working and there was no way of knowing if the the radiator fan was on (the gauge suggested not).

Fortunately, traffic started to move and we got off the motorway at the next exit (1/2 mile)and the temp very quickly dropped to mid position again.

After a few miles I checked the water in the expansion bottle which had risen by about a centimeter (the engine was still hot and engine bay fan now working).
I left the car over night ... water level has returned to normal ... and no signs of mayo in the oil.

Obviously, something went wrong, where do I start looking ... some of the above is probably relevant.
Any suggestions gratefully recieved.

Many thanks
RL Lane

>> My fan seems to come on when the guage reads just under half way. <<

That is normal for the F :o)

>>If I have a fast drive, not stationary the fan is on when I stop. <<

That's pretty normal too: the rad will struggle to disperse the excess heat without any airflow through the rad - hence the fan comes on.

>> it does go off when I switch off the engine( it doesn't run on ) nor does it come on when I stop. <<

There is no water circulation once the engine is switched off: the K has a mechanical water pump, so leaving the fan running after ignition off would be pointless, as Will says (although Dave and I have been working on an electric water pump installation).
Rob Bell

>> We got stuck in traffic for about 15 mins and temp gauge started to rise from its normal mid positon (less one mark).
It slowly moved up to within a couple of marks from the red. <<

A classic case of the radiator fan not coming on. If faced with this situation, your best bet is to turn on the heater to full heat and the fan to full speed. This is enough to stop the engine overheating until you can fix the underlying problem which can be one of the following:

1. seized or failed rad fan
2. blown rad fan fuse
3. failed ECU water temperature sensor.

In terms of frequency, (3) is the commonest. More details on his can be found here:
Rob Bell

Thanks for the advice Rob and the link to www.mgf etc ...

As the water temp sensor is screwed into the block, I guess I will loose some water when it is removed.
Is it enough to warrent bleeding the system?
I read somewhere that air locks are a problem on the F.
RL Lane


If you're quick you'll lose very little coolant. I've managed to DIY change the sensor, so I'm sure you'll be able to :-) No need to bleed the system.
Dave Livingstone

First check that it is the sensor.

Unplug the sensor and run the engine - if the fan spins up (even when cold) then it is the sensor - if not then the problem is elsewhere.
Will Munns

As Dave says, water loss is pretty minimal when changing the sensor - so no worries. :o)

The quick check to ensure that the fan is working is to disconnect the sensor plug with the engine running. The rad fan should come on immediately. :o)

Let us know how you get on! :o)
Rob Bell

Just for the record:
front fan will come on 95C and go off at 88C, if the car is equiped with an EFI ECU (PTP guys).

mgtffront fan will come on 95
Dieter K.

Thanks for all your replies.

My car has a working front fan and it doesn't get hot is stationary traffic, but when on a long run at around 90 the temp starts to rise. I think I have found the problem - there are about half of the vanes missing on the rad. By vanes I mean the crinckled bits of matel between the thin tubes on the rad.

I imagine that the higher temps associated with the engine working harder at faster speeds mean that the rad cannot disperse the excess heat?

It also seems to me that the rad appears to be in a "box" at the front of the car and the heat generated cannot easily escape, the only way out is back under the car and then inot the engine bay?

Maybe some vents like the Elise would A) help and B) look great?

Any comments anyone?
Kevin s

You may also have a lot of air in the rad and even an airlock too Kevin - what has the coolant level been doing? I think that you're going to have to book in for a rad replacement ASAP.

Regarding an Elise like arrangement - it's a cool looking mod, and it has been done: see the MG TF 200 HPD as one example - Tony's pictures can be seen here:

Also, there's a guy on the XPF who has done exactly this too - but I am having a heck of a job trying to find the thread...argh!

Basically, it isn't a bad idea (I actually really like the concept) - especially if you don't plan on selling the car. Unfortunately, if you value your car's resale value, don't do it...
Rob Bell

The water pump was replaced recently but I have checked the bleed valves and only coolant seems to come out, no air bubbles....

With regards the bonnet idea, I was going to find a cheap 2nd hand bonnet and work on that, If I ever wanted to sell the car I could simply bolt the old one back on!!

But hey, the darkside is growing stonger (young skywalker) I overtook a Passat TDI yesterday, he didn't want me past and sat right up my a*$e at 110, I know those TDIs are very grunty but still.

I know the VVC revs to 7250 but is there any point going that high or is a change to fifth worthwhile at 6500?

Going to order an SU 52mm TB today, air filter next and then plumb in my airbox
Kevin s

I found that XPF thread I was talking about:

Kevin, I thnk that you'll find it rather interesting! ;o)

The Darkside calls!
Rob Bell


I cannot access the pics - any chance you can post them here or email to me?
Kevin s

What's your email address Kevin?
Rob Bell
Kevin s

YHM :o)
Rob Bell

I have contacted the UK distributer and they have only just received stocks from the Italian people, no prices yet but the interseting thing is that they have apparantly had loads of calls in the last few days for the part!!!

They are going to call me back on Monday with a price and availability.
Kevin s

Go for it Kevin! :o) It looks stunning doesn't it?
Rob Bell

Feedback (Rob/Dieter)

< The quick check to ensure that the fan is working is to disconnect the sensor plug with the engine running. The rad fan should come on immediately.
Let us know how you get on! >

Thanks for the advice and links ...

I followed the three steps on the link you suggested and checked the 15A fuse under the bonnet first ...
The fuse had blown so I replaced it ...
warmed the engine on the drive way and waited for the temp to rise to just above normal running posn.

The engine bay fan came on so I checked the new 15A fuse ... it had blown.

Am I correct in thinking that this must mean that the temp sensor is doing its job and giving an input to the ECU ... which in turn is giving an output to the fan (maybe through a relay)..?

So, I guess there is a short circuit somewhere on the fan or in the wiring to the fan...

Managed to get to the fan from under the car and it seems farely free to turn???

Would be gratefull for any suggestions or maybe even a circuit diagram ..?

RL Lane

unplug the fan (if it's the same as the 400 then there is a plug on the rear of the fan) then retry - if the fuse does not go again then the problem is the fan
Will Munns

it's said the is harness below the front is prone to get worn for some reasonand does a short circuit then. Check from below as Will suggests.

.. and when it blows cause of fan failure instead,
Swap it to a 20Amp in any way.
30Amp Fuse will not hurt though.
----- ADVERT alarm ----
I've still some 'anti' steam kit's with fuses for sale :)
Almost website donation :)
-------- alarm end -----------

Dieter K.

Tried to remove the connector this morning ... its difficult getting in to the fan through the slot and the connector appears to be retained ... has anyone tried disconnecting the fan before.

Thanks for the replies ... my wife is a bit happier knowing that I'm not the only sad person with nothing better to do on a Saturday evening than talk MGFs.

Cheers again ...
RL Lane

Sounds as though you are getting somewhere Richard. I suspect that the fan may have seized - but Will's test ought to nail the problem to a circuit short or the fan... :o)
Rob Bell


a similar case came up in our DE Forum today. Sold the guy one of the funny kits. He wanted to install and found the fuse blown _already_. Fuse changed, blown again. Same as RL Lane.

Including RL Lane it's the third guy of about 45 within the last three month.
One had a small piece of wood clamped in the fan. *removed and repaired*

Two now are obviosly with short circuit.

"MoD" thinks :
*nightingale, I hear you knocking* !! ;)

Come on, anyone may tell me it's coincidence only.

Dieter K.

It's a case for the X-files Dieter! ;o) LOL
Rob Bell


Thanks for the replies ..

I think I need to invest in a Workshop manual or CD.

To get the fan out looks like a major strip down and its probably worth having a circuit diagram as well.

Any suggestions ... CD or manual etc ... and where is the best place to get one from.

Has anyone considered putting an overide switch in so the radiator fan can be activated at any time, bypassing the ECU temp sensor and ECU etc.

The fan probably siezes up through not being used ... I don't burn rubber and have never seen the temp gauge above midway and cannot recall the rad fan ever coming on in the 18 months of ownership.
(I must put my foot down one day ...)

If it does not come on in normal driving conditions it would be good to spin the fan up occasionally to keep it running free.
It could also be a backup for the motorway/traffic jam overheat situation I experienced.
As you have probably noticed I have lost a bit of confidence in the cooling system due to this and the many reported HGF.

Any Comments ..?

Richard (age49 and 7months) (Xreg)
Richard Lane

It might be possible to reach up and attempt to rotate the fan to see whether it has seized or not before removing the bumper Richard. Raise the front of the car securely, and crawl underneath...

Circuit diagrams you can download from Dieter's website:

The workshop manual you can buy on CD from either your local MG dealer, B&G etc or from eBay...

I'm not convinced that you need an auxillary override switch, but I understand your logic. Should be pretty easy to do too.
Rob Bell

Just a brief update ...

Remember the motorway traffic jam ... then the overheating and no rad fan coming on?

Checked the 15A fuse, it had blown.
Put in a second that also went ...
Unplugged the fan ... checked for a short circuit with a meter, no short circuit. Okay so far.

Checked the fan was spinning ... it ran freely for about 1 turn and stopped.
Nothing to compare it to except my wifes Focus ... both fans span on with very little effort.

Removed the fan from radiator and rigged it on the bench with ameter and 15A fuse etc.

It fired up no problem running steadily at 7.5amps after a current surge on starting. (Too high to read on ameter).
Left it running for about 10 mins and the current dropped to 7amps ... guess it has started to loosen up a bit.

Are you still with me ... hang in there.

Armed with this data I have contacted my local MG garage ... reading between the lines, the fan can get a bit "stiff" after a few years if not frequently called upon.
Hence the higher starting current which pops the fuse.

The fan should run at approx 5A. mine runs at 7amps on the bench and probably a bit higher in the car against the rad.

So to the solution ... take a flier with a bigger fuse ... 20A, or by a new fan 95.56 MGR.
Could I use a better fan..?

Either way ... yet another way to collect an HGF.

Comments welcome..?

Richard Lane

No more comment required (dieters sale)
Will Munns

No harm fitting a different fan - but a 20A fuse seems like a sensible way forward, as this is exactly what MG themselves fit from new on the TF... :o)
Rob Bell

Thanks for your input guys.
Confidence restored ... a 20A fuse it is.
Richard Lane

This thread was discussed between 06/09/2004 and 20/09/2004

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