Volvo KAD 32 Screaming Turbo's

[Ian Brown]

Recenlty purchased two new complete Volvo KAD 32 Compressor Turbo's as my old one's made such a high screaming noise when they kick in at 2000rpm. Having replaced them with new ones at £488 for the pair.

I have exactly the same problem with them screaming a high pitched noise like metal on metal. Can anyone help with some advise?

Regards

Ian

[doggypaddle]

have you checked for air leaks in the manifolds and pipework? turbo air leaks can reall scream.
a tip to find air leaks in turbo pipework is to spray an aerosol around the joins when the engine is idling, the engine note will change when the aerosol gets sucked in. you can use easystart, but be careful to keep the area well ventilated, and keep it away from the air intake as it will give a false indication!
check all the high pressure pipework from the turbo to the manifold and dont forget the compensator pipes and head to manifold gaskets.
it can help to restrict the air intake a bit with your hand too so there is more suck!

failing that get some to drive the boat with the engine hatch open and use a pipe as a stethescope to source the noise best done on a calm day!. when doing this its best not to get the pipe tangled in the alternator belt!
its unlikely to be the turbos if you have replaced them.

of course it could be something completley different

[ian parkes]

Where's Bob
I can't remember what its for but --
There is a small centrifugal governer on the top left of the engine that kicks in and makes a noise something like you describe . If you watch the engine as it revs up you can't miss it .

Maybe you have seen this but your description sounds just like it . Bob and I wondered what the noise was on his boat

[Searider]

Have you replaced the compressors (belt driven) or the turbos (bolted onto the exhausts)?

The compressors are normally pretty noisy, and it's not a pleasant noise either, almost like a gear whine.
The electric clutch on the compressor will screach a bit when it engages and there might also be a bit of belt slip. Does the noise go away once you go above 2800/3000 rpm?

Turbos should only give a bit of a whistle, although could be a bit of a screech if you have your ear close to the intake.

[ian parkes]

Originally Posted by Searider

Have you replaced the compressors (belt driven) or the turbos (bolted onto the exhausts)?

The compressors are normally pretty noisy, and it's not a pleasant noise either, almost like a gear whine.
The electric clutch on the compressor will screach a bit when it engages and there might also be a bit of belt slip. Does the noise go away once you go above 2800/3000 rpm?

Turbos should only give a bit of a whistle, although could be a bit of a screech if you have your ear close to the intake.

That guvernor I am on about is on the compressor pulley , its the top belt

[jwalker]

Originally Posted by doggypaddle

...a tip to find air leaks in turbo pipework is to spray an aerosol around the joins when the engine is idling, the engine note will change when the aerosol gets sucked in.... it can help to restrict the air intake a bit with your hand too so there is more suck!...

Except that manifold pipework after the turbo charger is pressurised by the turbo compressor so any leaks are outward.

[jwalker]

Originally Posted by ian parkes

That guvernor I am on about is on the compressor pulley , its the top belt

That's not a governor, it's a clutch and it shouldn't make any noise other than a firm click as it snaps on. However, they and their bearings do fail and can make metallic sounds.

[Nos4r2]

Originally Posted by jwalker

Except that manifold pipework after the turbo charger is pressurised by the turbo compressor so any leaks are outward.

Not when it's on intake stroke while idling.

[jwalker]

Originally Posted by Ian Brown

..my old one's made such a high screaming noise when they kick in at 2000rpm.

[doggypaddle]

Originally Posted by Nos4r2

Not when it's on intake stroke while idling.

JW may have a point though, the KAD 32 has a belt driven supercharger too in which case the pipework may be under pressure at tickover but only after the rootes blower.
i hadnt realised Volvo used compound charging until i looked at the KAD32 engine data.
Various different terminology used by different manufacturers dont help.
i generally call an exhaust gas driven centrifugal supercharger a turbo-charger, anything else mechanically driven i call a super-charger, whether its gee rotor, rootes blower, or a centrifugal blower, although a lot of manufactures call mechanically driven centrifugal compressors turbos too. confusing!

Well spotted JW.

[jwalker]

On my KAD300 and I'd guess the KAD32, the supercharger blows at tickover while the engine comes up to working temperature. Then the clutch releases the drive from the belt and it drops to normal aspiration until the throttle is opened.

I don't know the change over revs for the 32 from supercharger to turbo but it's possible that when the supercharger clutch releases at speed the bearing, which then comes into action within the clutch, begins to scream. This would coincide with the turbo coming on song and could easily be presumed to be a turbo noise. Just guessing.

[doggypaddle]

that would make sense, its probably a sealed ball race in the middle of the blower clutch?

[ian parkes]

Originally Posted by jwalker

On my KAD300 and I'd guess the KAD32, the supercharger blows at tickover while the engine comes up to working temperature. Then the clutch releases the drive from the belt and it drops to normal aspiration until the throttle is opened.

I don't know the change over revs for the 32 from supercharger to turbo but it's possible that when the supercharger clutch releases at speed the bearing, which then comes into action within the clutch, begins to scream. This would coincide with the turbo coming on song and could easily be presumed to be a turbo noise. Just guessing.

Thats the sound i thought could be confused with a turbo bearing, i had just lifted the cover while bob was driving and seen that clutch kick in and start to scream , by the way it expanded I presumed it was some sort of governer It does make a fair noise when the cover is off
Anyway its all clearer to me now what was going on there .

[doggypaddle]

Originally Posted by ian parkes

Thats the sound i thought could be confused with a turbo bearing, i had just lifted the cover while bob was driving and seen that clutch kick in and start to scream , by the way it expanded I presumed it was some sort of governer It does make a fair noise when the cover is off
Anyway its all clearer to me now what was going on there .

Do you mean it makes the noise when the clutch disengages and the turbo charger takes over from the rootes blower? if so theres probably a pair of £5 bearings in the middle you can press out and change like on an aircon clutch?
I have done a few of them, silent with the aircon on, scream like a banshee when you turn it off.

[ian parkes]

Originally Posted by doggypaddle

Do you mean it makes the noise when the clutch disengages and the turbo charger takes over from the rootes blower? if so theres probably a pair of £5 bearings in the middle you can press out and change like on an aircon clutch?
I have done a few of them, silent with the aircon on, scream like a banshee when you turn it off.

Its hard to say if the noise is normal without comparing it to another one . Its randski's boat and i just had a brief look at it after helping him fit new belts . When the revs increase to about 2k I guess ,the centifugal clutch opens up and there is a whirring or whining noise . I thought it was just the noise the compressor made ,
but if the clutch releases when it expands and the compressor stops turning and a bearing inside the clutch begins to spin then yes there could be a bearing making the noise in the clutch .

i thought the clutch was switching in the compressor as the revs increase and the noise was the compressor working

[doggypaddle]

my understanding of compound charging is the turbos do the high rpm boost, the supercharger does the low rpm, and the supercharger disengages when the turbo starts to build boost, so if the noise starts at 2krpm then i would guess its the bearing n the middle of the clutch thats U/S
probably best to take the belt off and check the bearing with the clutch disengaged, if the bearing fails completley then the belt could do a bit of mischief too!

[jwalker]

Originally Posted by ian parkes

Its hard to say if the noise is normal without comparing it to another one ....

There should be no noticeable noise from the clutch. The blower makes a kinda mid range shoooooshy hiss.

...the centifugal clutch opens up and there is a whirring or whining noise...

The clutch is electrical in operation. You should be able to find the wires and a connector in the vicinity of the clutch. You could check for a faulty clutch by increasing the revs a bit and the clutch should engage and be silent. Disconnecting the cable will prevent the clutch actuating and you would then hear the noise, if any.

[ian parkes]

Hmm 2 different theories here , don't remember seeing any wires etc the clutch is on the front of the pulley top left as you face the engine driven by a multi v belt and its silent untill the revs increase , comes in with a heavy click and appears to be centifugal force that does it .

I would like to see a manual

Are all Cad 32's the same? do they all have turbo's and compressors ? do some just use a compressor and no turbo ? I dunno never seen one before Bobs

[doggypaddle]

you probably wont see the wires, they will be tucked around the back well away from the belt like on an aircon compressor clutch.
I am not saying its not centrifugal but i think its unlikley, to work properly it needs to disengage when the turbo generates boost so its more likley to work of a manifold pressure switch? after all the boost the turbo generates its not rentirely rpm reliant but load too, so the rpm at which it needs to disengage may vary. I suppose there could be a big overlap though, any i digress.......
sounds like you found the problem though!

[jwalker]

Compressor and clutch

Note the cable and connector hanging from the clutch. The actuation is magnetic and the cable supplies the current to energise the electromagnet.