Defender 90 TD5 - Whistle on over-run

Hello all - MOT was due last week and as I am currently unable to work on the Landy myself, had it serviced (and top end of injector loom replaced) at the same time. It failed the MOT on brakes so had a new servo fitted. Drove it today and there is an audible transient whistle on the over-run when changing gear…at least in the lower gears…the rest of the Landy symphony drowns it out after the change to third. I have seen a number of posts about continuous whistles and am assuming that the cause of mine is probably the same…but would appreciate input from the wisdom of the forum! Thx in advance.

Update on my post from Friday. Blipping the loud pedal at rest does not induce the whistle, there are no sign of splits in hoses and the manifold studs all seem fine...no signs of soot or hot gas escape anywhere that I can see. The air filter box does not quite seat properly along it's front edge and no amount of persuasion will get it to sit right - but there's no obvious gap. Any thoughts?

You say servo was replaced, check the vac pipe and fittings. As there were no problems before I would look in that area.

If it only happens with the engine loaded then it could be the turbo.
My exhaust manifold started to blow slightly but that produced a squeal, and it was worse when the engine was pulling.

Does it only happen for a second?
Maybe a turbo wastegate issue not opening properly.
Don’t know the TD5 setup so that’s all I can say.

J

Thanks all! Will check the servo..had not thought of that. Am seriously hoping it's not the Turbo - that might take some explaining to the boss!

marjon said:

Does it only happen for a second?
Maybe a turbo wastegate issue not opening properly.
Don’t know the TD5 setup so that’s all I can say.

J

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Thanks Marjon. Whistle dies down over 2 or 3 seconds on each gear change - and I don't hear it when the engine is under load, only on the over-run.

Yep sounds right.

it’s the “boy racers” whistle

When under load it is using all the boost available, when you let off it still has pressure that the engine is not needing. Should go out the wastegate/over boost, if not it will whistle it’s way out somewhere else.

As I said I am just guessing as don’t know the TD5 setup.

J

Thx Marjon - although as a 60-something retired bloke driving a Defender, boy racer could not be further from the truth! Logic of the waste gate makes perfect sense though….more homework for this week.