SILICONE HOSES – BLING OR BLUSTER?
My Discovery 2 Td5 is due a new set of turbo hoses. They have been on since new and the car has now done 147,000 miles and seems to have lost a little power and there is a high pitched whistling noise. I understand they can delaminate inside, restricting the airflow. Is this likely and, if so, would it restrict the airflow? Are the coloured silicone hoses any better than the OE hoses from Land Rover? What do you think I should fit? Neil Coates, Rochdale
Hoses used to delaminate on earlier Land Rovers, but only after a long time. Standard hoses are of good quality, but after a lot of use, heat, and especially oil contamination (partly caused by failure to flush out the intercooler at regular intervals, or a defective engine breather system), can soften and then don’t resist the pressure changes within the system. For example, when accelerating, the increased turbo pressure may cause a weak hose to expand, thus defeating the pressure momentarily. Likewise, when decelerating, a weak hose could be sucked in slightly, though this shouldn’t make a difference because you’d be slowing anyway.
A hole or a split in one of the induction hoses may cause the whistling noise. But it’s more likely to be a blowing exhaust manifold gasket, the manifold itself may have become warped or a couple of the fasteners securing the manifold to the head may have snapped. Lift the engine’s acoustic cover and look for signs of black soot on the cylinder head adjacent to, and along, the top of the exhaust manifold.
Your lack of power could be caused by a split in an induction hose, or a loose hose clip. But there are plenty of other possibilities such as wastegate problems or engine oil travelling down the injector harness by capillary action and reaching the ECU connections. This can cause misfire, though it’s not easy to hear on this engine. It would be reasonable to replace the induction hoses (and the clips) at this stage anyway, but if you still feel a loss of power, some investigation of the engine and fuel system would be the next step.
I’m not aware of any worthwhile comparative tests, but OE hoses can be expected to do their job perfectly. That said that silicone hoses are more resistant to expansion when the turbo boost pressure increases, thus the delivery of full boost pressure is more instantaneous, eliminating any pressure lag that might occur with a more flexible hose material. Ed Evans
Here is an old and new Genuine hose that fits the turbo outlet. I’m applying equal pressure to both, and you can see how soft the old hose (right) is These silicone hoses are on a 300Tdi engine. Pictured (left to right) is a turbo outlet to intercooler and intercooler to engine inlet