Coolant Temperature 5008 hdi 2011

[amazighman]

Hi all.
I finally put my 5008 2.0 hdi back on road , before then I changed the cooling thermostat and replaced coolant .

On my first test drive I noticed that temp gauge goes up to 90 , but occasionally it falls to 80 ish , depending on driving , never lower than 80's

Could it be air pocket in system ,or my new stat/ temp sensor is duff , or its normal for it to behave like that?

Stat was Motorad brand that came in a Denso Box

Any ideas?
Thanks

[Arkis]

It seems like a bubble to me. I have 1.6 HDI and bleeding it was pain in the ass. No matter what I did the bleeding screw did not take all bubbles away. By the capacity of fluid I put in I knew there is still some air. I just gave up and drove the car normally. About half a year later I heard splush coming from the engine and when checking over I noticed the coolant was about 1/4 lower in the expansion tank... Yeah, the car bled itself after that long with a big fat noise as the bubble popped in the expansion tank.

Also dropping temp as you drive is quite normal too. The engine heats up and thermostat opens. That opens new circuit where the fluid is still cold and it will drop overall temperature as it mixes with hot coolant. It will happen only once during one drive tho. So if it is repeating multiple times during one ride, there might be bubble at the temp sensor.

[amazighman]

Thanks for that.
I have a feeling its a bubble in the system , didn't help it that I did fill the cooling system upon Stat change and left it for sometime ,some air might have trapped in awkward places i guess

[amazighman]

Whats the ideal operating temperature on these engines?