Supercharger whirring under load

[Cheyne92]

Hey everyone, just recently purchased a supercharged VT Calais and have noticed that it is making a bad whirring noise when under load with the a/c on, as soon as you turn the a/c off it revs nice and smooth and a hell of a lot quieter. All pulleys including supercharger spin freely with out noise when belt removed. It looks as if it has had new snout put on the supercharger with a smaller pulley, oil level is good s/charger as well. Any ideas? Thanks in advance

 

[BlackoutSteve]

I can't see how the accessory belt can can affect the supercharger just when the A/C is switched on.
Have you removed the supercharger belt and ran the engine with the A/C on? Take it off and go for a drive.. Can't hurt anything, it will just be underpowered.
It could be either or both belts making the noise, as a bad belt can sound a lot like a bad bearing, or it could be your A/C compressor. Does the whirring switch on and off as the compressor cycles on and off automatically?

Also, carefully inspect the s/c and acc pulley's bearings that are mounted on the same pedestal above the compressor. If either bearing fails, they will destroy the pedestal and you'll lose both belts.

 

[Cheyne92]

I haven't ran it without the belt on the supercharger but I'll give it a go tomorrow, as for when the a/c cycles on and off can't say I've noticed a difference to the whirring. Say for instance you hold it steady at 2500rpm and then switch the a/c on there is decent decrease in revs and it really seems to struggle to rev out. No hesitation/miss just a lot slower and noiser you can really feel a massive difference

 

[dirty hands]

IF not the air con compressor bearing
then its an idler pully or the bearing in the super charger

 

[Immortality]

Aircon pumps do suck a bit of power. I'd be looking at the A/C pump.

 

[Cheyne92]

I've ran it without the belt on the s/c and it didn't seem to make the noise, but hard to tell as it would barely run and kept wanting to stall. Really need to get it hot to find out, not sure I want to with it running like that

 

[BlackoutSteve]

Strange. I had to run mine without the s/c belt for a day or two once.. Ran completely normal except for no additional power above where the air bypass would have allowed the s/c to produce boost. Hot and cold..
The bypass valve should allow completely normal running at low engine load/high manifold vacuum.
How's the general condition of the engine then? Plugs? Injectors? Oil consumption?

 

[Immortality]

^^^ agreed. Something else may be going on here as the engine should run OK without the blower running.

 

[Cheyne92]

Yeah that is strange, definitely has to be something else. Plugs are brand new, leads are all good, and have replaced one of the coils. That fixed the miss I had before. I replaced all the baskets and o-rings on the injectors, still need to do fuel filter. I've also done the intake gaskets and s/c base gasket. Starting to think it may have a slight head gasket leak to, seems to be excessive steam coming out of the exhaust when it's hot

 

[BlackoutSteve]

Doubt a head gasket but it is possible. They make a very good seal.
Get the cooling system pressure tested if you think it's losing water. Even a comp test may reveal a lrak or a crack (perish the thought).
I have heard of people plugging the vacuum ports and/or overriding the linkage on the bypass valves. Maybe the previous owner did something, or maybe the hoses are perished. Still wondering why it wouldn't run normally.