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MG MGF Technical - m.o.t. failure and overheating

Just purchased a MGF VVC,took for an M.O.T. failed on emmissions and overheated while this was taking place(fan not cutting in).headlights dipping to the right.
Before the MOT I changed the oil filter,oil,air filter and plugs.The MOT guy thought the emmissions could be the sensor on the exhaust manifold,Can anyone help - Thanks
R Gowland

Hi Reg,

Seems any MGF that has stood for a while is almost guaranteed to blow the fan fuse. Replace with a 15A and it shouldn't happen again. Headlights go dim & lose beam pattern, but usually no problem aligning them. Or do you mean someone has fitted LHD headlamps..?

The lambda sensor is a likely suspect if the emissions are up, there is a method for testing it but I've not actually done it (yet) but someone better informed will be along shortly. Dirty or corroded electrical connections can also be the cause, many is the time a squirt of electrical contact spray in the right place is a full cure.

If there's any gap in the service history where cambelts might not have been changed, now would be a good time to check them out, and the tensioner too. Takes some wriggling to get the cambelt cover off, but worth the effort as you can also check there are no small leaks from the water pump (small enough that they'd never manifest themselves as a drip off the bottom of the cover); overheating a K series is occasionally a once-is-enough case for something to begin to let go, and early detection is a Good Thing. Sadly, MGR didn't specify a coolant level alarm until the TF years, and being so frugal with coolant the K series has to be looked after attentively. To rub salt in the wound, the temperature gauge is pretty useless, particularly in its reaction time.

If you're at a loose end on Monday, you'd find about the most MGF knowledge in a 50 yard radius anywhere in the paddock of Castle Combe circuit, where MGs On Track are having a track day (bathed in sunshine we can but hope)
Mike Hankin

Hi Mike
I owe you a fiver,your diagnosis was completely correct - temperature sensor.
The car has just passed its MOT
The car has left hand drive headlights,to pass the MOT I have had to put converters which was done on the headlight machine in the garage
During the emmissions test at approx 3000 RPM ,the power steering light came on and there was no power steering,after a couple of minutes the light went out and it corrected itself.
Is this a normal fault are you aware of.
Many thanks Reg
R Gowland

>Is this a normal fault are you aware of.

That's no fault. It's correct in that way.

>During the emmissions test at approx 3000 RPM ,the power steering light came on and there was no power steering,after a couple of minutes the light went out and it corrected itself.<

The amount of assistance given by EPAS is related to road speed,if the system sees high engine speed with no/very low road speed it turns itself off giving the alarm light.I think.
Pete C

Yep, safety feature. Full power steering at 70 mph on a motorway would not be good.

I would like to thank everyone for their comments they have all been most helpful.
I gave the car a good run at the weekend approx 300 miles and the little lady run superb
R Gowland

I would just add to the above info regarding the fan fuse. Change it to a 20amp rather than the 15. One of the reasons being that if it hasn't been used for a while there is a chance that a sudden power surge could blow the 15 with horrendous results i.e no fan = HGF.
Paul Carugati (MGF and MGBGT)

Thanks for the correction Paul, I wasn't convinced I had the numbers right.

Reg, good to meet you, glad to hear your trip was worthwhile ;o) I'll let you put that fiver into your tank, in gratitude for the fact that I didn't have to do any hands-on investigation, which invariably leads to pain and blood loss... If you'd hung around, you'd have witnessed how much power MGoT have over the weather - yet again, the rain held off until the day was over and people on their way home. We like that ;o)

I suspect you had to mask the headlamp beam quite heavily to dip the right way? If the net result is candles for headlamps, I may have an almost perfect solution for you - email me (mike at to hear more.

For the sake of the archives, the brown ECU temperature sender was apparently the cause of the emissions being high - if the ECU fails to get any input from the sensor it assumes 'cold' and richens up the mixture accordingly.
Mike Hankin

This is a message for Mike Hankin
I have tried to email you with no luck,so my email address is PS the car is still running superb
R Gowland

This thread was discussed between 06/07/2007 and 10/08/2007

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