9 replies to this topic

[essexminiman]

Hello al,

My first post here and 1 of many I hope.

First of all, I have three Minis. A 1970, 1070cc Mini cooper, a 2004 1.3i and a 1961 Astin mini, converted to a cooper "S" with a 1480cc engine sitting on a TranX, 5 speed straight cut gearbox, fornt mounted rad and discks all round.

Anyway, the subject that I am after advice is to do with the cooling on a 2007 1.3i. my friend has one of these as well as me. She drove to London the other day and noticed that the engine was running a bit hot. She then realised that the radiator cooling fan was not cutting in.
I tried all the normal things yesterday and still no joy. I swaped the temprature sensor from my 1.3i and on disconnecting it whilst the engine was running, the fan ran fine.
So! it is not the fan, it is not the sensor, could it be the ECU (Ihope not) or is there another sensor elsewhere?

Over to you....


Daniel.

[Jammy]

A 2007? They stopped making the Rover Mini in 2001?

Could quite possible be the temperature sensor, cheapest thing to replace, but if you've got a multimeter you could just measure the resistance of it (hang in a bowl of water and heat).

[essexminiman]

Hi,

I have tested the sensor against the one from my mini and the resitance is the same at the same temprature.
I also swaped it over and there was no change.
If the sensor is dissconected for a second or so, the fan cuts in and remains running constantly.

Thanks.

Daniel.

[essexminiman]

Hello again,

It is looking very much closer to being the ECU as the temprature gauge does not get above normal, even if the car is about to boil over.

I will delve into the ECU when I get a chance to get into the workshop (very busy at work). There can only be an electronic reason why this is happening as the signal from the sensos must be prossesed within the ECU before it is sent to the MPU.
I will connect the ECU as a mock-up on the bench and have a probe around inside.

I will let you all know the outcome and as to how servicable the ECU's could be. It may be that I can analyse the output from the diag connector (this can only be in digital, serial format) and maybe build an interface and write some software that could read it.

Wish me luck.

Daniel.

[BoyracerAU]

Try swapping the radiator caps. Perhaps pressure is the problem here?

[ICAM]

is the fan running when the engine overheated?
Sometime when the fan carbon brush is about to finish, is goes intermittent before fully not working.

[essexminiman]

Hi,

the fan is working fine. If you dissconnect the temp sensor for a second or so, the fan cuts in. Therefore the fan and it's relay are OK.

At normal running temp, the resistance of the sensor is fairly low 200 Ohms or so. The sensor must be loaded within the ECU to give it sufficient range for the MPU to act on the data maybe as part of a bridge or potential divider.

The fan will be controled from that data I.E the MPU will switch it on and of at the programmed points (on at 105 deg and off at 98 deg) according to the Haynes manual.

The signal to the temprature gauge is also from the ECU (as an analog level) and the guage will not go over half way, even at boiling point. The logical expaination would be the sensor, but that has been replaced.

The ECU that I have on my 1480 Cooper is one that I designed, built and programmed myself and that uses this principal. It is also controling a digital dashboard using LCD's for all the guages on a single wire, serial data bus, along with the coded igintion and radio alarm system.

I will get to the bottom of it and let you know the outcome and remedy.

Thanks to all for your help so far. All the info is useful.

Daniel.

[BoyracerAU]

Daniel, did you check or swap the radiator cap?

My understanding is that the cooling system is dependent on the correct pressure to maintain higher boiling temps. If the pressure isn't right, it could boil over even though the temperature is actually normal.

[essexminiman]

Daniel, did you check or swap the radiator cap?

My understanding is that the cooling system is dependent on the correct pressure to maintain higher boiling temps. If the pressure isn't right, it could boil over even though the temperature is actually normal.

Yes, sorry, I did not mention that. The cap is fine and the coolant did not start to boil untill about 116 deg.

Daniel.

[essexminiman]

Ok,

Here it is.

The problem is now sorted. I unpluged the ECU, left it for about 5 mins and pluged it back in. I ran the engine with a digital thermometer placed in the radiator battery at the top left corner (near the inlet hose).
The themostat opened at 88.1 deg, the fan cut in at 105.4 deg and out again at 97 deg.

So problem solved.

Thank you to all for your sugestions. I will keep using the forum and may be able to help others in the future. My 1480 cooper comes of the road in a week for a full refurb and the 1.3i is in the garage at the moment, because I bought it from my ex-partner, drove it for about a week and the gearbox gave up. Never mind..... So I will be re-building the gearbox next week.

Thanks again.


Daniel.