Squeal Noise thru turbo - Excessive clearance or what

Hearing squeal noise like fan hitting metal cowling and has come on suddenly.

08 GU CRD 127,000KM - NADS, single Dawes/Needle valves, 3"H/Flow, EGR solid plate fitted at exhaust manifold, TIG I/C.
Run max boost around 21-22psi, Good spool. Good EGTs (ecu remap).

Can stop noise on the fly by slowing spool (open needle from 3/4 to 2 turns), hot or cold. No noise when cruising on hwy and comes on when the eng boost/spool drops right away (rapid deceleration) and remains whilst spool comes up again with the increase of pwr / load until cruise spool again when noise stops.

Initially thought it was a leak on the boost side or @ turbo its self. After ruling out boost ducting and hoses, I removed the air inlet ducting at turbo flanged alloy elbow. Then with veh stationary, engine revs @ constant 1200 RPM with needle valve closed (no boost measured), picked up the constant metallic squeal noise and appears to come from inside the turbo inlet throat. Opened needle 1.6 turns and noise stops.

Removed alloy elbow off inlet side of turbo, inspected comp wheel and there is approx 0.010 – 0.015”" side slap (clearance). Checked by moving end of shaft with fingers. The OD of comp wheel can touch turbo housing bore. With a mirror and torch can see slight rub marks on the turbo housing bore (slight hone marking opposed to being a well machined finish).

First noticed the noise few days back when up the mtns (1200m), packed up to come home, warmed eng up, pulled out of camp easy 4WD pocking along then bringing on pwr @ nom 2000 RPM and heard the squeal noise Seemed to vary in pitch going thru rev range but mainly under load and when increasing spool and boost from 18-2200 psi. Noise came and went and then out on hwy, I was able to control it (stop noise) by reducing spool rate (open needle) from say 3/4 to 2 turns. After settling into cruise boost (hwy), was able to close needle to normal position (3/4 turn) and no noise.

Cold or hot eng, it does not have any impact on squeal noise generated.

All vac / boost hoses, TIG I/C and ducting look good. I do get a bit of turbo whistle and it is not that.

Thanks Hodge, for your earlier comment.. Will remove heat shield to inspect manifold and egr pipe for leaks. Fun times..(never done it)...LOL

Hope you are all still with it, very wordy.

What do you blokes think is going on?

Worst mechanic ever me with even less turbo knowledge. Do them suckers-blowers have opposite bearings inside that can possibly wear/off-kilter spasmodically maybe?


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New little about turbos a week ago myself. Not sure if a pair bearing on blower shaft. A wild guess, could be only one race but appears to be worn for it to look as it is touching side of housing bore. Read that they have some movement when new but would not recon so much to touch housing. Its not like a foot in a over sized gum boot but does moves about.

CRD and Zd30 I know commonly warp their turbo manifolds so they leak.
I wonder if this has happened to yours.

Guess I will attempt to take of the heat shield today and have a look around. So many bit in the way that need removing and will impact on running eng.

Looking up around dump pipe flange to/and manifold, egr pipe no soot evident from what I can see with shield in place,

The noise appears to be related to comp whl speed variation and maybe if it is out of balance the wheel throws and runs out and clips the housing slightly (effects from inertia and centrifugal forces):

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Removed alloy elbow off inlet side of turbo, inspected comp wheel and there is approx 0.010 – 0.015”" side slap (clearance). Checked by moving end of shaft with fingers. The OD of comp wheel can touch turbo housing bore. With a mirror and torch can see slight rub marks on the turbo housing bore (slight hone marking opposed to being a well machined finish).

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Originally Posted by drgtr

CRD and Zd30 I know commonly warp their turbo manifolds so they leak.
I wonder if this has happened to yours.

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Do you know how to check for this?

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Originally Posted by Bidja

Do you know how to check for this?

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Take the heat shield off and look carefully for black sooted area. It wont be much but you will find it if its leaking.

Then you can fix it two ways.

Required to take manifold off first anyway.


Use two gaskets and putty it up in between. This works well but I prefer the second way which is get it machined properly.

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Originally Posted by drgtr

Take the heat shield off and look carefully for black sooted area. It wont be much but you will find it if its leaking.

Then you can fix it two ways.

Required to take manifold off first anyway.


Use two gaskets and putty it up in between. This works well but I prefer the second way which is get it machined properly.

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Agree, if it is leaking, would definitely have it machined to ensure that faces mate well. Will inspect, Thanks

I am leaning more towards the turbo is at fault. The comp wheel runs out due to bearing side slap resulting from excessive bearing wear and the comp wheel is making contact with the turbo housing bore. As stated above there are witness rub marks on the turbo housing where the comp wheel is scraping the bore. The surface finish is typical of a light hone, opposed to being a well machined finish like the rest of the inlet bore.

Need to identify a new turbo that will handle my boost, tune and provide good low rev torque. Current ECU Remap spec is Max B 20-22 psi and AFR 22:1. Currently run max boost around 21psi, get max boost @ 1800rpm and max torque of 374 N-m with 95 kW at 2800rpm.

If its an exhaust leak or a turbo flange leak the tell tale sign of soot is what to look for. Mine was the same but the noise went away when the motor heated up. I had snapped a stud the first time. Second time round was due to the #$@* who fixed it the first time being a dodgy bastard resulting in me getting all faces of the exhaust manifold and turbo machined again and correct studs put in

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Originally Posted by growler2058

If its an exhaust leak or a turbo flange leak the tell tale sign of soot is what to look for. Mine was the same but the noise went away when the motor heated up. I had snapped a stud the first time. Second time round was due to the #$@* who fixed it the first time being a dodgy bastard resulting in me getting all faces of the exhaust manifold and turbo machined again and correct studs put in

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Growler makes and excellent point.

Change all your manifold studs when you take it off too. They either want to snap or the threads have stretched.
They are cheap enough too.

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Originally Posted by growler2058

If its an exhaust leak or a turbo flange leak the tell tale sign of soot is what to look for. Mine was the same but the noise went away when the motor heated up. I had snapped a stud the first time. Second time round was due to the #$@* who fixed it the first time being a dodgy bastard resulting in me getting all faces of the exhaust manifold and turbo machined again and correct studs put in

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Good move to replace exhaust manifold stud when they look at all suspect (good advice).

Crawling all over it, no soot marks yet but could be hiding. My noise is present when engine is hot or cold, that is why I started looking at turbo. Noticed the comp wheel bearing play and saw that the comp wheel can touch housing.
Noise occurs at faster spool, that equals more load on turbine wheel so more misalignment of the shaft in the bearings and could cause the excessive misalignment hence the noise. Could have over revved the wheel shaft as running 21psi boost.

To hedge my bets, unless a leak is found, looking at upgrading the turbo and the air flow ducting.