Hello everyone.
This is my first post here and unfortunately it is regarding a technical issue I am facing.
I have a 1990 Uno 45S with approx 80000 miles on the clock.
The problem I am facing is that when I am driving on the motorway with 5th gear, the engine temperature goes slightly higher than it used to.
This happens only under these conditions and it doesn't happen i.e. in heavy traffic.
Also I have the feeling that the performance is slighly lower than it used to.

Some history:
The engine has recently had a blown gasket replacement, new radiator, new thermostat and a new water pump.

In the attached photo, the needle shows the usual temperature in traffic conditions.
I have also drawn two lines. The green one shows the temperature the engine used to operate in the motorway and the red one shows the current one.

Any suggestions?

Thanks!

Have you set the intake air lever to summer ?
Contacts of the gauge board often corrode.
So don´t worry as long as there´s no steam out from the engine bay.

How do you set the air lever to summer mode to cars equipped with the air filter box as shown in the picture?

The first time I noticed it, I stopped the car immediately and opened the bonnet.
There was no steam or any other suspicious boiling water sound coming from the engine compartment.

Also the car has had some electrical problems in the past, mostly due to corroded ground contacts so maybe I should indeed check for false indications.

Well you can let check the ECU faults memory (there is a special plug under the dashboard) to see if anything is not working properly.
Also check faulty hose ends and leaking air.Electrics corrosion is often an issue in an old car.
Your version has the automatic summer/winter air inlet.

There is no ECU in mine. It is a carbureted version!

After some research, I have narrowed down the possible reasons to to a water circulation problem.
Before proceeding I would like to confirm something.
I heard that cheap radiators have been the cause for such kind of the problems as they don't allow coolant to circulate properly.
When I replaced the radiator, I installed a cheap £25 one. Not Marelli or Valeo.
Has anyone heard about this before?

no idea of poor quality radiator..??

have you flushed the ENTIRE cooling system with clean water..?,
checked / changed the thermostat..??,
charlie