Engine noise suggestions?

[Andrew S]

This s not my engine but I have a similar noise sometimes on idle but definitely when pulling away under clutch biting point. Had the noise for well over a year and engines only done 80k. New belt fitted no difference

https://youtu.be/R3WzXMhyrQU

Any suggestions appreciated
Cheers
Andrew

[bvs]

We had a rotating noise start on our Polo 1.4 a couple of months ago,I did not take any risks and got the cambelts/tensioner/water pump/aux belt replaced by an indy VW specialist.

[littlepolo]

Did you have only a new belt fitted or also pulleys, water pump, etc.?

[alexperkins]

Could be clutch release bearing

[Andrew S]

Ok, today finally got round to removing the belt and wow, noise gone. Presumed and replaced new belt tensioner and alternator tesntion wheel. All done and noise now back.
The air con pump seems to be the problem when I listen with a stethoscope I can here erratic knocking.
What puzzles me is that you seem to hear this noise when steering is on full lock or when youre pulling away. At low revs. Why should it do that?
Looks like it’s eBay pump and get it topped up
Thanks
Andrew

[alexperkins]

Checked the power steering pump?

[Andrew S]

Ah no, will do
Cheers
Andrew

[Andrew S]

The noise is coming from just below the alternator and o have aircon. The steering pump is under the green top up lid isn’t it? If so that maybe too far to the right

Are all the aircon pumps the same?
Cheers
Andrew

[alexperkins]

Yes that’ll be the air con pump. All the same but it’s a garage job as you’ll have to purge and charge all the refrigerant.

It could be the bearing on the air con pump as It has an electronic clutch built in

[Andrew S]

Thanks
When I ran the engine without the belt on, no noise at all so has to be something turning. I grabbed the pump pulley and couldn’t get any movement by hand. Put stethoscope on pump and could hear intermittent rattle on case but not on Alternator, exhaust or engine sump.
Still can’t work out why the air con pump would grumble when engine idling and using the power steering on maximum turn. Maybe it just puts a load on engine and plays with the air con
By the way, the pump makes the noise with air con off too

Cheers
Andrew

[alexperkins]

Sounds like it could be something else then. That is a weird one

[Andrew S]

Had the noise for well over a year now and car used daily.
As said, with belt off, nothing at all, silent and smooth. Can only mean something driven off a pulley. Stethoscope only picks up noise on the pump, nothing else but as you say weird as to why putting a strain on the steering you hear it clearly
You hear it when pulling away at biting point and sounds like a bag of nails or Diesel engine
Thinking about it, you can hear a harshness from inside the car with air con on and idling when driving after a short time and then you turn air go off and it goes.
Looks like an eBay replacement pump, thick glove and get the gas out and swap the pumps over and get it topped up by garage
Can’t wait to get it sorted as it’s a different car when the noise isn’t there

[RUM4MO]

The air con compressor does not have a clutch, it is continuously driven but is a variable displacement type of compressor so as demand for cooling increases, so its displacement is altered, this means that there is always a small amount of R134A being pumped round the system and also means that the load applied to the engine is dependant on cooling requirements so overall saves fuel.

One thing also to consider is, when you are demanding steering assistance, quite a high level of current is being demanded from the alternator, so at idle this current demand will mean taking a lot of current out of the battery and the alternator will be getting max demand to replenish it - so the load on its older/worn bearings will be very high and so it will/could be making a lot of noise.

Replacement power steering assembly, be very careful when picking a replacement as typically it will need recoding - it is not just the pump that you will be replacing but the entire electronics control pack as well, leaving only the steering angle sensor which lives in the column/rack.

[alexperkins]

Thanks Rum. Didn’t realise the 9n was displacement as the 6N2 was a clutched air con compressor

[Andrew S]

Thanks Alexand Rum
I was wondering if a non air con drivebelt could be fitted so that I could cut out the air con to prove the issue?