Engine sound when pulling away 9N

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Andrew S
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Engine sound when pulling away 9N

Post by Andrew S »

Hi All

Stupid question, but would I be correct in thinking that as the engine on my daughters 1.2 Polo is a 3 cylinder, when you pull away from stationary, it starts off sounding like a diesel? It sounds for a short while as if the plastic under stray is loose but its not. If you rev the engine in neutral, there is no noise at all, only under load.

As I say, its a stupid question but compared to the daily BM we drive, its a different animal :)

Cheers
Andrew
colingZA
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Re: Engine sound when pulling away 9N

Post by colingZA »

Hi there,

Yes, the three cylinder engine is a little diesel-ish in sound. Even the newer Polos that are 3 cylinder are rather 'raspy'.

Regards,

C.
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

Thanks for confirming that :)
Cheers
Andrew
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

Managed to find time today to video the noise that I am referring too.

Its a 9N 1.2 16V 2005 engine and only done 80k miles

If you blip the throttle quickly at low revs or when pulling away slowly you get this noise but also I can feel it through the pedal. Its not, but it sounds like under tray vibrating.

I am wondering with such movement with the engine tipping as to how the exhaust copes. Are both engine mounts shagged or is this normal

If you rev its slowly, its quiet and very smooth as can be seen in one of the clips

https://youtu.be/rq0jv91XHcc
https://youtu.be/Sc1uwLcyzmY
https://youtu.be/Wj38V4Y6WEI

Any help and comments appreciated

Cheers
Andrew
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

Bump
Thank you
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

How much should the engine rock when revved or when pulling away?

Thank you
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alexperkins
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Re: Engine sound when pulling away 9N

Post by alexperkins »

A little but not a huge amount. If you can rock if when the engine is off relatively easily it’s a sign the engine mounts are past it
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

Thanks Alex
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

I need to look at this again as its a pain.

I have replaced the lower rear engine mount and all seems to look OK but to be honest, not being too familiar with the car, I could do with some suggestions

When you pull away, especially from cold, it feels like the there is either loose trim or engine transmitting through the bodywork only in the drivers front corner. You can feel it through the body shell as if something is touching. When I say touching, its like the exhaust is vibrating under the floor but in the front corner only and improves when warm or the engine is hot. Cant see exhaust touching anywhere. It has done this now for many months and hasn't got worse, just embarrassing when pulling away as you can clearly hear it outside of the car.

Could it be:-

Bumper fixing, but then again why would it be worse when cold?
Water pump bearing? Would there pump quieten down when warm?
possibly the drive belt tensioner spring as I can see the belt has polished the top of the sump or whatever it is under the bottom pulley although the local garage said that was normal. Do they wear and become sloppy?

I'm thinking the fact that it seems worse when cold must be a clue
When cold, you can hear something vibrating or transmitting noise when its just ticking over

Engine I think is in great shape as it doesn't lose water or use oil

Any other suggestions much apprenticed

Thank you
Andrew
Andrew S
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Engine sound when pulling away 1.2 9N

Post by Andrew S »

Hi All

Been having a look at noises from the engine offside area

This is done with ease using a bar, but should the mount be this soft and low down?

https://youtu.be/hDv2Hg-Mhhs

https://youtu.be/x5dNmevJUh0

Also, when i look a the belt, it has or is touching now and then as can be seen by the shiny patch below the pulley, would this be a stretched shiny pulley or the tensioner? Cant feel any play by hand on the tensioner and I suppose if the coil spring has broken, it would allow play and very noisy

https://uk-polos.net/download/file.php?mode=view&id=454

Any feedback or advice appreciated
Cheers
Andrew
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RUM4MO
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Re: Engine sound when pulling away 9N

Post by RUM4MO »

That is a horrible noise!

These engine mounting are very compliant so I'd think that they are okay.

The shiny bare metal area - I'd think that you should be concentrating on working out why that has been happening and stopping it.

Sorry no more ideas!
Andrew S
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Engine sound when pulling away 9N

Post by Andrew S »

Thanks for quick response

Presume the belt can either be stretched as its very very shiny or the tensioner has weakened. There again, I'm not convinced a tensioner with that sized spring can weaken. That only leaves a soft or stretched belt, can't be anything else surely.

Although then engine mount is captive rubber and may not be knocking, a soft one would surely allow the engine to rock more and even the exhaust movement would be affected etc

The mounts appear a reasonable price Borg and Beck I have seen for £35'ish on ebay so maybe worth replacing anyway, not sure

Thanks again
Andrew
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Re: Engine sound when pulling away 9N

Post by RUM4MO »

I'd only expect the exhaust to touch the body under certain sudden engine loading conditions as the drive train will flex in its mountings in reaction to its load change.

For instance, I had the front flexi replaced by a proper exhaust builder - he did not get delivery of the correct size of flexi so just fitted one diameter size up and length size down, car seemed okay apart from an annoying slight resonance or other noise when driving on a level road. The next day I reversed it up our steepish driveway and the noise was terrible - okay let the revs drop too far and exhausts and drive trains do make horrid noises when labouring. In that case we failed to agree that his work was at fault as I am only a DIYer, so I bought in the correct flexi, paid him to replace it, which he still said would not make any difference - and that returned the car to being as good as new!

Back on topic, from your video clips, that noise seems to be coincident with a snap/step change in demanded engine speed - and any issues with the crank end float, auxiliary belt tensioner or anything else in that area, should still be the centre of your investigation.

Tip, with the engine warmed up, remove the auxiliary belt - then see if there are any noises, if they have gone then you know where to look - auxiliary belt or associated parts, if the noise is still there, I'd be checking the end float of the crankshaft by trying to move that bottom pulley in and out, or even check that bottom pulley.
Andrew S
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Re: Engine sound when pulling away 9N

Post by Andrew S »

Thanks, that is a good suggestion about removing the belt as the engine will still run, will do.

I did fit a new exhaust last year all bar the flexi pipe, will look into it

Cheers
Andrew
Andrew S
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Re: Engine sound when pulling away 9N

Post by 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
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