2018 Fiesta ST temperature still rise fast when idle with upgraded radiator

[MaxY]

Hi everyone, I live in LA and My 2018 fiesta ST's coolant temperature will rise very fast when stopping at light or idling with AC on. It will go all the way to 230 and I suspect it will eventually overheat if I let it stopped long enough. And when stopped the AC will not blow cool air. But as soon as I am moving, the temp will slowly fall back and the AC will immediately blow very cool air. I have already upgrade to CSF triple bypass radiator and when driving normally the temperature stay under 190 with ac on full blast so it seems the system is working at this when moving. But once stopped and AC will start blowing warm air and the temp will slowly raise. Has anyone else experience similar problem? what else can be faulty? I just checked the radiator fan and it is working. the car is bone stock except the radiator. Appreciate all the help, thank you all.

 

[M-Sport fan]

You have to check the fan relay and it receptacles in the fuse panel for melting/corrosion, and if that is fully OK (or replaced), and you still have the climbing temps, the fan module/controller or any of the connectors/harnesses going into or out of it may be corroded, faulty or burned/melted.

But first thing, even before any of the above is to check to make sure all of the connectors are fully seated and plugged into their receptacle sockets correctly.

How long ago was the radiator replaced, and did you do it, or was it installed by a shop.
DIYers, as well as shops have been known to forget to plug all of the fan connectors back in properly, resulting in your problem.

 

[madhatter]

what M-Sport said. fan doesn't sound like it is coming on.

 

[RAAM]

I am having basically the same issue, fan not turning on, jut getting my very long parked FiST up and running again and noticed this today when doing some leak testing while idling. It got hot pretty quick so I did a top gear 60MPH drive as highway just up a short hill, cooled it down quickly. Temp "gauge" was maxed out, oil temp (inferred) on the AccessPort showed 236 and came down quickly as well. Parked, temps seemed fine and held steady then all the sudden had a serious water leak under the car I could not find the source of. Now I have two issues, hope just a bad hose, loose connector on the WG water cooling line perhaps...but the fan one might take more time to sort out.

What I need is the wiring diagram, I had all the factory manuals from when I got the car back in 2014, digital ones, and they got lost in the change of computers over the years, anyone have a link to them?

Thanks,
Rick