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MG MGF Technical - Low coolant light

Some time ago I had the engine management warning light come on solid amber. My local dealer (usually pretty good, they still have most of the MG team there in the workshop) said it was a problem with the engine bay cooling fan. Eventually they fitted a sensor to a loose cable that came from the loom that runs by the coolant expansion tank and the amber light disappeared. Where is the ambient air temperature sensor normally located? Is is really next to the cooling system expansion chamber?

My F is an 06 registered TF160, but was probably manufactured late 04 early 05. Dieter's site suggests that it should have a low coolant warning system installed, at least according to the VIN number. However, the expansion chamber has neither float or cables. The service guys say they've never seen a low coolant sensor on a TF.

Now last night my wife told me that the low coolant light was on, coming on just as she reached home after a 12 mile or so trip from work in some heavy traffic.

Could it be that the low coolant light is on as the new ambient air temperature sensor is trying to turn on the engine bay fan?

I also had a problem with it overheating the other day, traced to a blown radiator fan fuse under the bonnet (not the one under the steering wheel). Could this have caused an airlock? There was no coolant loss, and hasn't been since the incident occurred. The dipstick shows clean oil, and the expansion change cooling fluid is clear as crystal.

The car's due in for its 3 year service next week. If anyone knows the part numbers for the proper expansion chamber with sensors, I'll see if I can get them ordered and fitted, although that still leaves the possible problem with the ambient air tempaerature sensor and engine bay cooling fan, and why did the radiator fan fuse blow?

I really have to make this car bullet proof as I've just had my company car taken away, been made redundant and offered the same job at a 30% drop in salary, which I can't afford to refuse - unless anyone knows of any good IT Manager jobs going suitable for an, er, somewhat more senior applicant? :-O
David Dewick


Sounds like lots of rubbish (Polite said: misunderstandings) from the usual good guys there.

>Where is the ambient air temperature sensor normally located? Is is really next to the cooling system expansion chamber?

Your model will have no sensor. Just above the expansion tank may be a bracket with an empty 1 inch hole which usually was the location for this sensor at earlier models.

> low coolant warning system installed,

Please compare: Should look like this.

>traced to a blown radiator fan fuse under the bonnet
Take care, the must be a reason, like a worn cable isolation (short circuit to the meatl work) at the front, below the car.
Or the fan got stuck by any reason.

> part numbers for the proper expansion chamber with sensors,
See above link, but it's useless if you don't own a TF with the required harness.

What is the VIN of your car ?
Please post to (confident use promised)


Hello Dieter

Thanks for the reply.

I found a thread on another board that detailed fitting the low cooland sensor and the noted that there was a spare connector on the loom that runs by the expansion tank with a green/black and black pair of wires that the sensor connects to. This is the connector that the garage have fixed the ambient air temparature sensor to. So, I think that the low coolant light comes on when this sensor detects ambient air temperature above 100 degrees C.

I'll give the garage the parts numbers and get them to fix them

But, what sensor causes the engine bay fan to come on, and where is the sensor located? When was the sensor near the expansion tank deleted?

Both radiator and engine bay fans worked ok today when I ran the engine up to normal temperature.

David Dewick

Dieter, slightly confused by your site. Are you saying it is possible to install a low level switch into the old expansion tank?

I would like to do this and am quite happy to connect the electrical bits if you could tell me how to fit the switch into the tank?
Robert (Bob) Midget Turbo

>Dieter, slightly confused by your site.

Me too, ;) I try to improve since 10 years ...
Need to add a picture of the new and of the old can.

OK, all that could be done by owners with an MGF or TF before VIN about 630000 is:

1. get a B&G coolant sensor Kit and swap it in
(They supply the same can and sensor as the original, but have developed an electronic device to make the signal audiable and visible

2. source another coolant level kit incl. ecu device where the sensor gets put into the coolant filler hole.(Duno the supplier, see archives)

3. do as I did, swap in the new can and sensor and attach a low power beeper.
(disadvantage: it almost beeps when you drive sharpe bends ) ;)
Material needed
1 Sensor PCJ000040
1 expansion tank PCF000140
1 buzzer 12 V max 20mA , # 63S1120 (20S1120)
2 pcs app 90cm long automotive cable
2 pcs 2.8mm isolated Faston Crimp connectors
2 pcs of 20mm shrink tube
some cable ties
more on the above site.

oops, I had your VIn alrerady. Thanks for resending today.

However your car was made short after the introduction of the original sensor unit.
As the connector is mounted, it's obvious that they at first put in the remaining stocks of the old (useless) tank.

As said, there is no more sensor for the rear engine bay fan.
The fan gets controlled by the ECU. (No idea how)
I only assume the build the on/off with help of the ambient inlet air temp sensor and the ecu coolant temp sensor.

Unfortunately (fortunately ? ;)) I don't own a TF so someone else may investigate and post the result.

This thread was discussed between 20/02/2009 and 22/02/2009

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