[SteveG]

A bloke at work also has an st but a diesel.
He had the engine management light come on and went into limp yesterday when planting it to overtake.
He said at the same time the heater blew cold which I find surprising. It returned to normal and he contined the journey
He also had seen the temp rise a couple of times lately but has (probably unwisely) ignored it as it settled quickly.
In the old days if you were overheating, just to get home you suffered a hot air blast from setting the heater to full to help engine cooling so I wondered why his heating went cold during this and also of course what might be wrong with his car.
Thoughts anyone?

 

[jameo]

I had a similar problem on my kuga, turned out to be a split thermostat housing, it’s plastic and a common part to fail, so the garage told me, temp shot into the red and went into limp then 20 seconds later all seemed ok, it happened a couple of times whilst I was towing my scissor lift and Plant trailer so the car was working hard, managed to get it back without to much issue, just took it steady and then found coolant dripping from under the car, not loads but enough to notice. All has been fine since the housing was replaced, happened about 4 months ago

 

[Alb]

If the heater suddenly goes cold it means there is no coolant flowing through it.
That could mean no coolant at all, an air lock or (least likely) a blockage.

 

[sttwoton]

The egr coolant jacket can spring an internal leak, on these Peugeot engines, bit of a faff to change, maybe you need to get it pressure tested.