Strange noise is driving me mad.

[bigcarpjohn]

Hi all,

My van has been making a strange noise that's been driving me mad. It's not a metallic rattle and it's not a squeak – more of a throaty/vibrating noise. It sounds like it's coming from the middle of the engine bay. It's quite subtle, but I'm the type who can hear grass growing!

It's most noticeable on the motorway at low RPM. For example, with cruise control set at around 60mph, when the van comes to a hill and is under load, I can hear it. I can also hear it when stationary at traffic lights.

Today, while sitting at some lights, I started trying to narrow it down. The van is a DSG T6 180.

• Put it in neutral – noise remained.
• Turned OFF the A/C but left the blower running – noise remained.
• Turned the blower off completely – noise disappeared.
• Turned the blower back on – still no noise.
• Turned the A/C back on – noise returned.
• Turned the A/C off again – noise stayed there until I switched the blower off.
• Once the blower was switched off and then back on, the noise disappeared again (until I turned the A/C back on).

The noise also disappears if I increase the RPM.

Any thoughts on what could be causing this?

 

[Dellmassive]

I'm thinking AC compressor clutch bearing.

See if you can get a video clip on your phone.

The closest you can get to the AC compressor is under the van, front. Drivers side..... They normally make a sqweel sound.

Other options are any pully in the auxiliary belt.

 

[Dellmassive]

What year and how many miles?

 

[DXX]

I'm thinking AC compressor clutch bearing

No AC clutch on a T6, maybe you mean the alternator clutch pulley?

 

[bigcarpjohn]

Its 106k 2016

 

[DXX]

De-tension the auxiliary belt and check the action of the alternator clutch pulley by hand. A defective alternator clutch pulley will damage the aux’ belt tensioner.
I can’t say if that’s the cause as I don’t know what a ‘throaty vibrating noise’ is.
You could record it and post it via YouTube etc.

 

[willythepooh]

My van has a cyclic noise similar on the lowest fan setting (1).
Very annoying when you tune in.

 

[whodat]

Something (small bit of plastic wrapping or similar) caught in vent/fan? Sometimes gets caught in fan? warped rubber grommit around that area?
Have you changed the Aircon filter? 10minute job - just make sure you know which way round it came out. If that is dirty - could it cause fan to work harder?

Keep us updated.

 

[DXX]

My van has a cyclic noise similar on the lowest fan setting (1).

Best not use fan setting 1 as it can lead to the thermal fuse blowing on the fan speed resistor pack.

 

[willythepooh]

It hasn’t yet after 52,000 miles.

 

[whodat]

My van has a cyclic noise similar on the lowest fan setting (1).
Very annoying when you tune in.

Yeah - unfortunately my van has that on setting 2 which is the one it is at all the time. (3 is too loud and blowy and 1 turns out breaks the van!)

 

[bigcarpjohn]

De-tension the auxiliary belt and check the action of the alternator clutch pulley by hand. A defective alternator clutch pulley will damage the aux’ belt tensioner.
I can’t say if that’s the cause as I don’t know what a ‘throaty vibrating noise’ is.
You could record it and post it via YouTube etc.

Ill try my best

 

[bigcarpjohn]

So here is qn update.

I took it to a couoke of places, both were saying DMF but in my head i couldnt work out why it would be so bad driving yet fine on tickover. Very ocasionally i got a rattle when stating for a split second.

Today we got it up on the ramp, we could see the dmf was fine when running. Took off the AUX belt checked the tensioner, tensioner was fine. Alternator pully wasnt sounding great; also AC pully was falling apart a bit. Ran it for a few sec9nds with no belt and noise was gone. New belt fitted and armed with a stethascope had someone sit inside foot on break and into drive, no noise from dsg turned on the AF and the pump spunded lije a box of spanners.

With that in mind do you think a pump on its way out, along with the Alt pully would case a small vibration under light load and coming to a stop?

Also has anyone had a AC Pump from auto doc? Or even anything from autodoc? They are showing a Ridex pump for under £150 and a Ridex Remf (one being brand new far east and one remanufactured in europe ) for £200

 

[DXX]

Alternator pully wasnt sounding great

The defective alternator pulley will cause the tensioner to bounce, hence the noise. The tensioner may feel OK now but it will wear out rapidly if it’s bouncing.
Ref my earlier post #6.
By ‘pump’ I guess you are referring to the AC compressor. I generally buy from Autodoc, the only issue I’ve had and it’s a major one …….Evri. Otherwise very good.

 

[bigcarpjohn]

The defective alternator pulley will cause the tensioner to bounce, hence the noise. The tensioner may feel OK now but it will wear out rapidly if it’s bouncing.
Ref my earlier post #6.
By ‘pump’ I guess you are referring to the AC compressor. I generally buy from Autodoc, the only issue I’ve had and it’s a major one …….Evri. Otherwise very good.

Thanks for that. Would you buy the recon oump or the brand new one? One is made in china one is re built in Croatia?

 

[DXX]

Thanks for that. Would you buy the recon oump or the brand new one? One is made in china one is re built in Croatia?

Well half the worlds consumables are built in China but I would avoid anything with bearings like an AC compressor. If the one from Croatia is re-furbished with Chinese bearings you’re also stuffed.
I might go down the OEM route from a breakers providing the ports have been blanked off.
It’s a bit odd for a compressor to fail at 106K miles, before you remove it check the pressure and get the workshop to weigh the refrigerant that’s vacc’ed out. If there has been a large leak and it’s running dry there might be debris in the system.
I’d visit an auto AC specialist and check that the compressor actually needs replacement.
Just because a component makes a noise doesn’t mean it’s defective.