Overheating and and rough idle

Hi all. I hope every one is enjoying the sunshine :slight_smile:
I have a bit of an issue of which I cannot overcome.

The engine overheats, especially during hot weather. I drained coolant and flushed ita few times, it was extremely dirty and rusty due to car bein sat for a long time. I bled it properly so no air left in coolant system. It didnt work.
I changed the thermostat, no luck.
I checked all hoses for leaks, nothing.
There is circulation when i check both top and bottom radiator hoses.
The fan turns on when it starts to overheat but its not enough to cool down the engine.
The fan turns on when it starts to overheat but its not enough to cool the engine down.

Maybe a blocked heat exchanger ? When you bled the system of air did you have the heat controls in the full heat position ? (not the fan speed but the highest heat setting) often gunk forms a bottle neck in the heat exchanger especially when sat for a while. You mention you have circulation but do you have it through the heat exchanger ? worth checking imho

or possibly sounds like a blockage somewhere or maybe a weak water pump.

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Ive also flushed the heater matrix, there is a perfect flow there. The only thing is a weak water pump (of which i had replaced when i changed the timing belt). Unless anyone has other ideas

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Check ignition timing isn’t miles out … can cause overheating and rough idle. Worth swapping out the radiator cap (cheap but wouldn’t point to rough idle)

When you rev it high, do you hear slushing around come from behind the dash? Sounds Like water leak?

I would get garage to test for head gasket as well .My guy used some liquid that goes green when it detects carbon in water. I had a pin prick size hole on rear head that caused the overheating on the red auto which still let me drive around 100 miles but when I stopped or stuck in traffic it would be overheating.

Amazing only a pin sized hole caused that.
Would compression test identify that?

Yes compression or better vacuum test the cooling system.
As greena28 pointed out it could easily be a head gasket problem.

Probably but fluid test does it quicker and easier than pulling plugs. I imagine it slowly overpressurised coolant. Final straw was arrived back home town and it stopped at some traffic lights and had to refill with load of water to get it home as it was so hot it would not start. Was perfect 2 hours later but obviously thats when it went t garage and the dreaded fluid turned green.

Take the radiator out and get it flushed professionally. If the cores are blocked it will overheat. I had the same issue. Best $100 I could spend.