Mondeo V6 1999 - Temperature gauge - Cicero


My water temperature gauge which has always read low, usually just off the lower end, is now showing no movement at all. Does anyone know how to test if the problem is in the gauge or the engine temperature sensor, please? I'm assuming the sensor is the one on the nearside close to the water pump etc.


Mondeo V6 1999 - Temperature gauge - Peter.N.

Its unlikely that the gauge is faulty - although not impossible, if the sensor only has one wire on it short it to earth and the gauge should then read hot.

Mondeo V6 1999 - Temperature gauge - elekie&a/c doctor

A Mondeo of this age will have 2 sensors,one for the engine control system and one for the gauge.Both are 2 wire devices.So you need to make sure you replace the correct one.While you are in that area,check the condition of the water pump drive belt.Hidden under a plastic cover,at the end of the cam box,over the gearbox.

Mondeo V6 1999 - Temperature gauge - bathtub tom

Your thermostat's at least sixteen years old (unless it's been replaced) and the weather's been a little chilly lately - if you hadn't noticed.

I'd consider replacing the thermostat.

Mondeo V6 1999 - Temperature gauge - Cicero

Thanks to all for your replies.

The non-reading temperature gauge pre-dates the cold spell by a considerable time, so it is not connected to that. The heater works fine so it may or may not be the thermostat. I accept that the thermostat is 18 years old but it is typical of this car that most of it is original.

The reason that I am concerned to understand the problem is that MOT time is approaching and last year the CO and HC readings were higher than I would like although, of course, still below the required limits. I wondered if these would be affected by poorly functioning temperature senders. If these are 2 wire systems how could I test whether it is the sender or the gauge. please?

This car has over 200,000 miles on the clock and is still drives beautifully and is mechanically excellent but, unfortunately, is suffering from corrosion on the rear wheel arches which is a worry at the MOT.

Thanks again for your help.

Mondeo V6 1999 - Temperature gauge - elekie&a/c doctor

The temp gauge operation will not affect emission levels.If the engine coolant temp sensor was faulty(for the engine control system),then you would have starting and running issues.If the co level is too high,then this could be an indication of cat issues.There are 3 on this car.

Mondeo V6 1999 - Temperature gauge - Cicero

A short update. The sensor is a one wire type. I tried shorting the wire to earth but it was so awkward to access by more than one screwed-up hand that I'm not sure I made contact. Anyway, no change observed on the gauge. I have decided to get my trusty village garage to replace the thermostat and the sender, then if the gauge still doesn't work I'll just leave it.

Thanks again for your collective help.

Mondeo V6 1999 - Temperature gauge - Cicero

Final bulletin: The problem was solved by replacing the temperature sensor and the thermostat (which was found to be in 2 pieces). Gauge now works normally, heater comes on sooner. Emissions also hugely improved, I had treated it to 3 tankfuls of Shell V-Nitro Plus leading up to the MOT to see if it made any difference. Maybe this helped, maybe not - who knows?


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