Front cooling fan

[Heinkeljb]

My 450 city coupe +passion (1999) has decided to beep at me because it is overheating. I turned on the interior heater and fan to full to try and reduce the coolant temperature until I could get to a safe place to pull off the road. Second problem, no hot air from the heating system! (Obviously an air lock somewhere in the system). I managed to stop on a garage forecourt, so was able to buy a litre of ready mixed antifreeze. When the temperature would allow, poured the anti freeze in - lots of bubbles and overflowing of the header tank. More water as required.
Finally got hot air from the heating system, but very soon after driving off, overheating again! Back on the garage forecourt, more water into the system.
Getting intermittent hot air from the heating system. Eventually, managed to get stable hot air from the heating system (it seems very hot). Managed to drive to work with no further overheating issues.
Drove home this evening with no overheating issues. I did have the interior heating on full blast!

Question: At no point during the overheating / beeping did I hear the sound of the front fan.
Question: Can you turn the front fan on using Star C3 diagnostics? If so where do I find it.
Question: Where is the sensor which should turn it on? Is it the normal temperature sensor on the thermostat - in which case that's working as the temperature gauge "blobs" went all the way up and that should have turned the fan on.
Question: Where is the most likely place for a leak? It must have one to develop an air lock out of the blue.

Any help appreciated.

John

[tolsen]

Most likely leak area is either radiator or tunnel pipes. Buy a cooling system pressure tester to find leak.
Temperature sensor is the one in thermostat housing.
Fan relay is inside Zee. Tested by selecting Zee with Star. Can’t remember how but not difficult to find.
Radiator auto bleeds through expansion tank. There is no auto bleed of engine so leak is therefore most likely in rear of tunnel pipes. Pipes are supported by a plastic piece each end. Years of vibration and external corrosion due to capillary action could be the cause.

[Heinkeljb]

Thanks Toslen,

Will look at things this weekend. Do you have a recommendation for a cooling system pressure tester? It's obviously not a very big leak as there is no puddles under the car. It bothers me that the radiator fan did not come on, so that will be the first thing I try and check, should also be the easiest if it can be switched on and off via Star Diagnostics.

John

[tolsen]

My pressure tester is similar to this one:
https://m.ebay.co.uk/itm/14PCS-Radia...10&_mwBanner=1

Here is photo my kit.

[tolsen]

Some clever sellers also include case into the count so many stupid buyers go for the 15 piece kits and overpay.

[tolsen]

Have you seen flashing temperature gauge more than once? Could simply be knackered cooling fan. After 18 years of service something got to fail.

[pinger]

You could hot wire the fan to the ciggy lighter socket.
Leaks leave puddles.....

[Heinkeljb]

Saw the flashing temperature gauge begining of the year when it did a similar thing. Had a thought that it might be the water pump, but water was circulating in the header tank both times.

John

[tolsen]

It is quite normal to loose some coolant over many years. For that reason it is recommended to check coolant level from time to time and top up as required.

[137699]

Most likely leak places in my experience are:
- turbo coolant pipes
- thermostat/housing
- water pump/housing

You need to get the car in the air with engine running and up to temperature and thoroughly inspect these places to find out where it's leaking from. They're incredibly difficult to spot because the coolant evaporates almost as soon as it surfaces in a hot engine.