Low temperature

I have a 2007 Renault Clio Series 3 1.5 dci 68 diesel. Since the car was new, the dash temperature gauge has only shown two bars when the engine is fully warmed up (the handbook says that normal temperature should show four bars on the gauge). The only way I can get the gauge to show the correct normal temperature of four bars is by running hard, above 60mph, for a few miles on the motorway. When I do manage to get four bars, if I switch off the engine and immediately start the engine again, the gauge is back to two bars, even though the engine has had no time to cool down.

The Renault Dealer told me Diesel Clios are all like that and that they take a long time to show four bars. I was not convinced, so I removed and checked the thermostat. This was fully-closed when cold and opened at the correct temperature of 83°. I also bled the cooling system at the heater hoses and thermostat housing – the heater gives a good output, so I am certain there are no air-locks. I also checked that the wiring terminals were clean and secure on the Temperature Sender Unit, which is fitted into the thermostat housing.

I am concerned that the low temperature reading from the Temperature Sender Unit may also be used to supply temperature information to the ECU and might affect its correct operation.

The engine starts promptly when cold – about two revolutions of the engine

– and even quicker when the outside temperature is below zero. If the engine is started when the engine is warm, it takes a bit longer to fire-up – about four revolutions of the engine. Otherwise, the engine runs well with good performance and good fuel consumption.

I would be grateful if you could tell me if this temperature gauge behaviour is considered normal with Clio Diesels and, if not, what would be the likely cause(s)? I would also be interested to hear your comments on why my engine starts quicker when it is cold than it does when it is warm. Jim Mclaughlin

The diesel engine will run colder when not under load and I would have no worries about the temperature reading you are seeing on your vehicle. If you want to ensure the engine temperature sensor is

should stop the cooling fan.

If the relay is not at fault, the problem may still be the coolant sensor. This can be checked by using an EOBD diagnostics device to read off the live data and ensure that the ECU temperature reading from the engine is realistic. when starting from cold, as we have to reverse the car first. It only occurs after slight use or during a journey, but very occasionally the clutch bite variation is also very haphazard and seems to have no discernible pattern. I suspected there might be a problem with an electrical connection, so I checked and dosed every accessible connection under the bonnet with penetrating fluid, but to no avail.

Have you any ideas please?

John Cook

The two issues are most likely connected. The system on your car employs a sensor on the gearbox to measure the speed of the gearbox input shaft. If this is too high for selection, the gearbox will not shift into reverse gear, but will display a zero rating, as you are seeing.

The problem may be a faulty sensor, but is far more likely to be the clutch centre plate sticking on the input shaft and being spun by contact with the flywheel. Your dealer should be able to confirm this by reading off the input shaft speed on their scanner. If this is the case, the gearbox will need to be removed and the clutch plate lubricated where it connects with the splines, to ensure it slides freely on the input shaft.

On the other hand, the problem could be electrical, in which case the connections should be cleaned with an electrical cleaner. However, the sticking clutch plate is a far more likely culprit.