S40: Overheating at speed

[moshejay]

Hi...any further news on this?

[rad01wel]

Here's my contribution to this issue - I had the same symptoms with my V40 GDi; it started to overheat at 70mph with the temp. gauge heading north at a rate of knots but cooled down rapidly once I either slowed down to 50mph or switched the heater on full. So I tried the following: -

1. Flushed the block, reverse flushed the block, and
2. Flushed the radiator, reverse flushed the radiator, and
3. Drained the system and replaced the coolant, and
4. Tested the thermostat (not the problem, it worked fine) - no impact from any of that, the car still overheated at speed
5. Replaced the engine coolant temperature sensor - I didn't really think this was the issue as it also operates the temperature gauge which appeared to be working fine but a new sensor was only £9.50 so it was a cheapish option - not the problem, had no impact at all, car still overheated at speed
6. Eventually decided to remove the radiator and do a "proper" reverse flush - once I had the bottom hose off (rusted jubilee clip was a bitch) I could see into the bottom of the radiator - there was a heavy build up of what looked like limescale which was clearly leading to reduced flow. So I replaced the radiator - a new one was £54 - replaced in about 90 minutes flat.

And the result - 12 points to the UK - sorry, Eurovision is over! It worked, the car runs like a dream now, no overheating at all. I have to assume therefore that at 50mph there was enough coolant flow from the radiator to cool the engine but at 70mph there wasn't. I just hope that the water pump hasn't been affected through all of this - there was a fair amount of crap in the radiator but no sign of broken fins, etc after the block flush so fingers crossed.