Help. Coolant in header tank cold & fluctuating temperature gauge issues.

[swinman]

Hi New to the forums. I have a Peugeot 2008 with the 1.6 HDI Blue 100 engine. I am having issues with the temperature gauge fluctuating, the car runs up to temperature then rises just below the red section then drops down to just above 90. I have had the car checked out by a auto electrician & he diagnosed the temperature sensor switch was faulty. I have changed the sensor, but i am still having the same problem. When I went for a test drive to see if everything was ok, I had the same problem, I only travelled a couple of miles up the road. I pulled over & checked the engine, the water in the header tank was cold. the top radiator & heater hoses were hot, bottom hose cold. I have heard that the water pump fails on these engines or the thermostat fails. Ive been quoted between £250 to £270 for an thermostat housing & £140 for a timing belt kit with a water pump. I don't know, if I'm honest which one to go for next. Any advice would be greatly appreciated.

[RichardW]

Generally a failed water pump will lead to overheating under load (i.e. climbing a hill) whereas a failed thermostat gives unreliable temperature control. To me sounds like the stat is faulty, but it could be the sensor leading you astray. Need to check whether it's really too hot. This weather, it will take a long time for the header tank to get hot, it's only an expansion tank.

[swinman]

Hi Richard. Thanks for your reply. Yes I was climbing a hill at the time... Also when I checked the header tank, when releasing the cap there was no pressure there & the water in the tank was stone cold.

[PaulC5]

I do not know how old the car is but the blue hdi engines started about 2015. If your car is this old it is getting due for a timing belt change so if this needs to be done it is not wasted money. You have not mentioned if the engine fan is coming on, this ought to be around 96°C so if the gauge is going up to the red section I would have thought it should be running - if not then something else that might need sorting. If you have a code reader that does live data you can see what temperatures the sensor is giving and when the thermostat is opening (should start around 90°C) and the top hose gets warm.

[swinman]

Hi. Update.... It was water pump failure, the impeller was intact, but it was turning on the shaft. The temperature gauge sits just above the 90 no issues. Thank you for your input & advice.

[CitroJim]

Excellent, useful to know I last had exactly that on a 2.0HDi in a Pug 407. Confused the heck out of several others who checked all the usual suspects and found them good...

A good excuse to swap the cam belt too. I trust you did the same whilst all was in bits...

[swinman]

Hi Citrojim. Yes new timing belt kit fitted.

[CitroJim]

Hi Citrojim. Yes new timing belt kit fitted.

Excellent!