Temperature

[Westauspug]

The temperature reading on the dash was always steady but now it constantly oscillates between 80 and 90.
I have changed the thermostat and the temperature gauge sensor but it still goes up and down once the car warms up.

[Rubyoptics]

Have you got A/C? Could be as simple as having very hot weather = you having the A/C on which is kicking in the cooling fan as causing the temp to cycle?

[GrandadMonkey]

When was the timing belt and water pump last renewed? Should be every 80,000 miles or 8 years, whichever comes first.

[Westauspug]

The timing belt and water pump are less than 2 years old. The temperature cycles with aircon off or on. It is currently winter here in Western Australia, 6 degrees C at nights 17 C during the day.

[IanL]

One possibility is restricted flow (perhaps through the radiator), such that the flow cannot quite cope with the heat generated by the engine, even with the thermostat fully open, with the fan on low speed. That would required the fan to perform high speed cycles to manage the extra heat. You could try flushing or even replacing the radiator.

[Westauspug]

The radiator was replaced three years ago and the fan does not go to high speed until the temperature reaches 100C and that only happens if I leave the car idling for at least ten minutes, the temperature then returns to 90 and then goes back up to 100 until the fan comes on again, I think that is a normal temperature cycle for when the car is idling. With normal driving the temperature cycles between 80 and 90, as soon as the car warms up to 90 with normal driving it then starts cycling but if I let it warm up in the garage by leaving it idling it goes up to 100 then cycles back to 90. The oil temperature is usually steady on 90.

[IanL]

I've been watching mine, and it does the same. Hard to tie it definitely to anything, but it is probably how much ram air is passing through the radiator in my case. On a small island, one is constantly changing speed, so the airflow is one variable and the engine heat output another. Reminds me of an aircraft oscillating in height and speed (I think its called a fugoid oscillation). Anyway, it holds the temperature between acceptable limits, so I don't mind.

[Westauspug]

Thanks IanL, I think I will just keep an eye on it and wait and see how it is in summer when we get days of 40C.

[Capncol]

Peugeots use an unusual system whereby the temp sensor reports to the ECU, and the ECU tells the temp gauge what to read. If you can get a good pro code reader on it and look at live data, it will show you what the ECU is seeing