SIL­I­CONE HOSES – BLING OR BLUSTER?

Land Rover Monthly - - Classic Q& A -

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

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