Diesel Turbo whistle question

As I have never owned a diesel car before is it normal to hear the turbo whistle ?

Its not loud but I can hear it if I rev up !??! Mate of mine says his Citroen is like that.

Putting out to the masses !

Yes it’s normal

Turbo diesels will always make a whistle noise BUT if the noise has got louder all of a sudden it’s poss an intercooler leak , or a split it an air pipe , this will def be the case if the car had lost power at the same time I.e turbo boost pressure is leaking out of the system .

no power loss that I know of how could I tell if there was power loss?

its prob always done it I have just never noticed (only had it a week )

only does it if I rev or apply more gas and its not loud at all

only does it if I rev or apply more gas

That’s generally how turbos work. (-:

I shouldn’t worry.

Some do it more than others – my Octavia vrs tdi sounds like it has an ambulance under the bonnet when pootling through 30 zones at low revs.
My Scudo van makes more of a hiss than a whistle.

it’s probably the dump valve – is it more of a “wish/woosh” sound? and happens when you depress the clutch/change gear?

its an auto diesel

stew1982 – Member
it’s probably the dump valve – is it more of a “wish/woosh” sound? and happens when you depress the clutch/change gear?

erm – don’t think that diesels have dump valves…something to do with not having a throttle valve, but can’t remember exactly. Molgrips’ll explain if he’s about….

edit – oh and it’s normal unless it’s getting louder or you are losing power or noticing loads of blue smoke in the exhaust.
A boost leak is fairly obvious as you’ll normally be chucking out a lot of soot when accelerating.

My VAG whistles too,( 😯 ) but you can only hear it if you have the window open, think its quite normal.

ski, you need to see a gynaecologist pronto.

If there is a boost leak the car will drive so slowly for so much right foot you will think it has begun to die. Listen to the engine with the bonnet up whilst a trusted mate (who won’t accidentally run you over)does big blips on the gas, it can be as simple as a hose clip that needs tightening up.

Old bimmer here, whistles all the time.

I’m pretty sure all turbo engines need to have dump valves otherwise the turbo would stop spinning straight away when you took your foot off the gas.

I’ve had a variety of diesels with almost no turbo whistle to quite loud whistling. Never an issue. Plus some older diesels that sounded like a bag of spanners rattling to a now a quite quiet diesel.

I’m pretty sure all turbo engines need to have dump valves otherwise the turbo would stop spinning straight away when you took your foot off the gas.

No, since a) diesels don’t have throttles, so keep pumping air through without any fuel, and b) most modern turbos have variable vanes so they can keep spinning without pumping much air (and thus don’t need to spin up much again when you put your foot back down, reducing turbo lag).

Start worrying when it stops whistling.

IF it still runs and doesn’t smoke don’t worry about anything.

If it was a boost leak there would be loads of black smoke out the exhaust.

Some diesels whistle when you let off the throttle but that is the exhaust resonating due the drop in pressure more so if they got a de-cat fitted.

Many thanks for all your help

de-cat fitted no idea ? its a Merc 270 cdi (2002 52 plate) if that helps

Dont worry about all the intermediate answers, the first one was correct.

As a general rule Turbo D’s dont have dump valves and with almost all standard cars you won’t have a dump valve anyway, you MAY have a recirc valve but you won’t normally be able to hear it.

It’s normal to whistle, if it whines or screeches, or hisses, it’s a potential problem, any other time just ignore it.

On the subject of turbo diesels, if I’ve got my foot on the gas and the engines at, say 3k RPM, the turbo will obviously be working/spinning pretty hard.

If however the engine’s in an over-run situation, i.e. foot off the gas but at 3krpm whilst engine braking down a hill for instance, is the turbo spinning/working?

Just wondering. I think not, but I’m not sure.

Turbo Diesels don’t have Dump Valves like Petrol. They have recirculating valves that force the unused air back into the system, they do have a waste gate so if the Turbo is being fed more air than needed it will divert through the waste gate.

The hissing you can hear is perfectly normal. The type and level of the noise differs from make to make, depending on type of Valve or how much Boost the Manufacturers run the engine at. Vauxalls for EG have a lot of Turbo Lag and are pretty placid on the power, My Golf GT TDI has a right kick on it.

A recirc valve is just a dump valve that puts the gas back into the engine intake rather than vents to atmosphere. They can still make a bit of a hiss when you lift off, certainly Golfs & Astras i’ve driven in the past did.

My Turbo (1.9TDi VAG ’96 reg) used to kick in around 3k rpm. Pretty bad mpg below the turbo, but damn good on the motorway!

I had a 53 plate 270 CDi and it did the same, it did have a new turbo fitted at 9K though but they assured me it was normal and it was coming from the air box, with it’s post contract lease owner now it’s up to about 160K and still runs fine and still does nearly 40mpg too.