1.4hdi 2005 overheating when on the open road

Good day to all.

I'm new to forum and a recent citroen owner.
I'm from south Africa.

As the topic states the car is c3 1.4hdi 2005.
When I drive short distances like to work and to shops and so forth the car runs fine and everything's good. As soon as I drive on the open road and accelerate to 100km/h (60mile/h) the car seems to overheat, or the gauge seems to go past normal running temp. I thought it might be the thermostat and replaced it, still same issue. And then the waterpump, replaced it and still same issue. The radiator was properly cleaned and unclogged about a year ago.
I can someone please assist me with the issue because I'm out of ideas.

Hello and welcome.

As your car is running OK some of the time it suggests to me that the temperature sensor is working correctly.

I'm just wondering if you have air in the cooling system causing an airlock?

You said you'd had work done on the radiator and also that you'd changed the thermostat. Was the system bled correctly afterwards?

Not something you maybe use often given your climate but does the cabin heater work OK?

As soon as I drive on the open road and accelerate to 100km/h (60mile/h) the car seems to overheat, or the gauge seems to go past normal running temp.

Hello

How many bars on the temperature display do you consider to be 'normal running'

And

How many bars do you consider over heating to be?

Hi and thanks for your responds I really appreciate it.

The radiator work was done by professionals so I would assume the system was bled properly. If it was bnot bled properly how can this be fixed? I can't take it back to the shop since my Financials can't alow it at this point

The cabin heater works fine, and yes seldomly use it in sunny south Africa.
In fact when the temp gauge passes normal, which I consider 3bars, please correct me if that's not right. I would switch on the cabin heater and the gauge Wil drop back in a minute or so to 3 bars... But still then I can't go any faster than 100km/h.

Im really stuck at this point and I'm afraid of something worse happening... Can it be headgasset?

Mine gets to 3 bars and stays there, never over.

If yous goes over 3 bars but can be brought back down to 3 by using the cabin heater it indicates a problem with the radiator efficiency and/or the bleeding that has been mentioned.

If it's not been bled properly it would just be a case of bleeding the system.

The system would need to be bled after each change of a radiator, water pump or thermostat if they were changed at different times.

It could be the head gasket but my bet is the radiator.
Have you owned the car since new?
If it was "unclogged" about a year ago I'd say the radiator is not running at 100% capacity.
If it needed to be unclogged they should have done a capacity test to check their work.

I didn't own the car since new... I only had it for about 6 months now... The reason I know the radiator was unclogged is because the previous owner's son told me. The car belonged to a old lady that passed away not to long ago.
I Wil get back to the car over since I'm working during the week.
I will give updates a soon as got something.