Volvo Cars are being forced to recall 8,500 of its popular environmental cars as they break down by the summer heat.

As The Swedish Wire reported last week, hundreds of Volvo-owners have been left by the side of the road as their vehicle suddenly dies. Oddly enough, the fuel pump breaks down when the outside temperature gets too high.

Now Ford-owned Volvo recalls 8,500 of its popular clean vehicle; Volvo V70 2,0 Flexifuel and Volvo S80 2,0 Flexifuel. Some 400 Volvo-owners have already been affected by the problems and all owners of the troubled models are now urged to hand in their cars for service.

“We are utterly surprised by the sudden origin of the problems", said Bo Larsen, spokesperson at Volvo Cars in Gothenburg, to The Swedish Wire. "It all occurred during the last few weeks when there’s been a heatwave in Sweden. We didn't know about the problem before that". 

The troubled cars are all produced between late autumn 2007 up to September 2008. Most of the cars are in Sweden, but also a few hundred in Germany, Ireland, Norway, the Netherlands and elsewhere.

What happens is that the non-return valve and pressure regulator in the fuel pump looses its grip, which stops the flow of fuel to the engine and the car dies. Volvo is currently investigating the problem to find out what causes the parts to fall of.

In April Volvo Cars recalled more than 20,000 vehicles across Europe over fears they have faulty cooling fans. The recall affects four-cylinder diesel engine models of Volvo's C30 hatchback, its S40 compact saloon and its sister model, the V50 estate.