1.25 14 plate fiesta. Engine overheated replaced head gasket, water pump cam belt, thermostat, water bottle cap.

Now as soon as it reaches temperature, engine starts to get hotter then idle gets iratic and stalls. If I remove oil filler cap. Instead of blowing it sucks. Compression slightly low on one cylinder. 

We have also replaced electric fan but still overheats. 

Do you think this is piston rings or another breather issue 

 

Thanks

Was the head skimmed or at least pressure tested?

40 minutes ago, TomsFocus said:

Was the head skimmed or at least pressure tested?

Yes both

11 hours ago, philldoddy said:

Yes both

Ok, that rules out most parts that could cause low compression.  Really the only part left is the piston ring.  Unless the new headgasket got pinched as the head was torqued down.

Sucking from the oil filler is odd though.  I'd expect the compression to be leaking into the crankcase with a worn piston ring.  Probably worth replacing the PCV valve if not done already but I'm not convinced that's the issue here.

So it overheats and despite throwing time and money at it, it still overheats. Worth checking that the radiator is not blocked. I would have started with a compression test and I strongly suggest that you carry one out before doing anything else and report your findings.