Its a 3 cyl engine 🙃, I haven't tried swapping the sides over but I have unplugged them one by one, the sound happened less frequently and quieter when I unplugged the injector closest to the timing belt side of the engine, although it didn't make the sound go away completely so I don't think it's related to the injector/ignition on that cylinder, might swap out the spark plugs regardless and I'll need to take a look at the belt for the squeeking but probably won't get around to anything till Sunday so I'll update then

25 minutes ago, LightRobin said:

Its a 3 cyl engine 🙃,

 Yeah I forgot that bit then.  

 

Course it also means you are paying less for new sparkplugs.  

 

Just taking the belt off, after you've got the engine fully warmed, might also quieten any noises from it's use perhaps helping to locate the knocking sound.

 

The old stethoscope trick where you use something to amplify  the vibrations/noise , screwdriver to ear /check bone /skull type of thing but be ware a running engine is hazardous and if you slip and damage your ear or eye you may sorely (perhaps literally) regret it possibly for the rest of your life. 

 

US Pro are a reasonable quality low price make of tools - US PRO Automotive Stethoscope Mechanics Engine Diagnostic Tool Probe 5389, 7 Euros including P&P - https://www.ebay.ie/itm/152736005277

 

Be interesting to see your update - don't hide it if it's a bonnet prop knocking.  

 

Good luck.

Edited 19 August, 20214 yr by nta16

Sorry, I forgot to put - I'd always do any type of servicing maintenance work, such as changing sparkplugs (if required) and test the result before going to the trouble of other work which would be additional work to what's normally required for service/maintenance such as removing the belt, or buying special tools but a simple job like spraying the manifold with carb cleaner or WD40 if they're readily to hand I'd also try.

 

And if you really want to know the cause and/or remedy you'll need to do one thing at a time and thoroughly test it.

 

I'm sure I've probably mentioned keeping the battery in a good state of charge to keep the computers happy or they'll really mess with the car and not necessarily throw up warning lights until it's too late.

 

A better scan tool would give info on the various sensors actual functioning.

 

As servicing (and many repairs) are just basically about cleaning and lubricating I'm a fan of next level servicing such as cleaning MAF and throttle body or at least a visual check for muck and crud.

 

I've rambled again, "nurse time for my coco".

 

Edited 19 August, 20214 yr by nta16

Yeah I'll change the spark plugs anyway, the throttle body had a bit of carbon buildup in it but nothing major, haven't talked a look at the maf and a better scan tool would be pretty expensive, especially one with live data so I don't think I'll invest in one quite yet

 

I wasn't thinking of you buying an expensive scan tool rather going to someone who has the correct system and can do a full reading and report for you and clear any unneeded codes.

 

17 hours ago, nta16 said:

You really need someone who knows what they're talking about, which ain't me and someone with a good VW scan tool there's only four marked on this map if it's still current and the person still wants to help out. - https://tinyurl.com/yn6mmtyk

 

 

The hyperlink in above takes you to a map of Ireland with perhaps four people who may be willing to help you by scanning your car and give you a report if you contact them, I've no idea if you're near any of them though.

 

Be very careful with the MAF sensor as it's delicate and you're supposed to use a special cleaner for it, I've no idea if ordinary electrical contact cleaner is suitable or not if it's not too dirty.  You could also check it and other sensors are the proper makes and numbers in case an poor quality aftermarket has replaced any of the originals.  Again a good quality scan tool would show what figures they're working at and you can look up if that's within usual tolerance.

 

As always you want your battery and all connections in good condition and battery in a good state of charge, the battery starting the car and the headlights seeming bright enough means nothing if the computers aren't getting enough electrickery to keep them fully happy.

 

Edited 20 August, 20214 yr by nta16

Ah right, I don't think its an issue of aftermarket parts since it only started making the noise about 5-10km after I did an oil change on it, that combined with it only happens when the engine is warm, could have something to do with the variable valve timing, maybe the computer changes the timing a bit as the engine warms up, as for the people with scanners there seem to be 2 of them 30mins away from me so I might see if they want to take a look

Don't think your engine will have a MAF sensor.

1 hour ago, Wino said:

Don't think your engine will have a MAF sensor.

Fair enough, what does it have instead (for the computers to be upset about, apart from everything else)?

 

What did you think of the video of the noise?

 

Edited 20 August, 20214 yr by nta16

A MAP sensor I should think. Manifold Absolute Pressure. Somewhere downstream of the throttle body.

Tend to be very reliable. 

 

i wonder if the OP has considered trying my suggestion from some time ago, about investigating whether the oil pressure warning system is functional?

1 hour ago, LightRobin said:

maybe the computer changes the timing a bit as the engine warms up, as for the people with scanners there seem to be 2 of them 30mins away from me so I might see if they want to take a look

As you've probably picked up I'd not over-rely on any computer and just about anything seems to upset them so best to see what they're moaning about, real or not.

 

Whilst the belt is off if you hold about 4,000 revs for a while to see if there's any start of turbo rattle or clattering. 

6 minutes ago, Wino said:

A MAP sensor I should think. Manifold Absolute Pressure. Somewhere downstream of the throttle body.

Tend to be very reliable. 

Thanks, another three letters to try to remember, what would a leak at the gasket or other do to that little computer minion?

 

 

8 minutes ago, Wino said:

i wonder if the OP has considered trying my suggestion from some time ago, about investigating whether the oil pressure warning system is functional?

 No doubt you'll discover the answer later.

 

The noise was before and after an oil change but with an oil additive added and if still using 10w-40 I'd do a hot and long drain and refill with 5w-30 by autumn before the cold weather but ready for it treating the 10w-40 (if it's still in the engine) as a running flush (changing oil filter too).

 

I haven't tried unplugging the oil pressure sensor, will add to the list of things to try tomorrow, 

17 hours ago, nta16 said:

Whilst the belt is off if you hold about 4,000 revs for a while to see if there's any start of turbo rattle or clattering. 

This engine doesn't have a turbo

Also I put 5w-30 in it when I changed the rod bearings

18 hours ago, Wino said:

A MAP sensor I should think

Just did a bit of research, you are indeed correct, it has a MAP sensor

48 minutes ago, LightRobin said:

This engine doesn't have a turbo

On listening to your video again with headphones what I thought I heard I didn't and all sounds different this time, sounds more engine like.

 

I've had three cylinder cars 599cc, 657cc, 659cc all with turbos, and a 997cc without turbo, that was from new and it sounded a bit rough when pushed but was fine and economical but I do wonder how it'd be at 100k-miles of use and abuse.

 

 

53 minutes ago, LightRobin said:

I haven't tried unplugging the oil pressure sensor, will add to the list of things to try tomorrow,

 As that's from someone who knows what they're talking about rather than me I think that'd be a good idea - and a scan with a VW program scan tool may tell you a lot especially with live data and if historical codes haven't been cleared.

 

 

56 minutes ago, LightRobin said:

Also I put 5w-30 in it when I changed the rod bearings

All good then, I wasn't sure which oil was now in there.  Interestingly I couldn't find the Castrol oil you put at Castrol UK but different markets have different versions of the same name and different availabilities.

 

Here's hoping it's something cheap like spark plugs causing the computers to play silly-devils.  

 

Time for me to be driven to and/or from drink.

 

Bois we've had a break through, went and got new spark plugs today and got to work, changed them out and got bummed when the engine still ran the exact same, the old spark plugs were in pretty bad condition anyway so no biggie. The I decided to take the alternator belt off, which in my car actually has a tensioner even the the service manual says it doesn't, anyway took it off and boom, no more foreign sounds, engine runs perfectly, first time hearing about an alternator knock 🙃, now I'm not sure if its the alternator or the tensioner but my bets are on the tensioner seeing as how the belt is loose enough to squeek when cold, mad at the fact that I changed the rod bearings over a bad tensioner pulley but we live and we learn, just glad to have come to a conclusion, thanks for the help and suggestions

Tensioner details here (view on computer, not phone to see all columns) connecting and mounting parts for alternator; pol... - Fabia(FAB) [EUROPA 2015 year] (7zap.com)

 

Just now, Wino said:

Tensioner details here (view on computer, not phone to see all columns) connecting and mounting parts for alternator; pol... - Fabia(FAB) [EUROPA 2015 year] (7zap.com)

 

You read my mind, I was just looking for the part number for that, thanks

any ideas what i could do to test if its the alternator or the tensioner making the noises?

also the tensioner at the link you sent looks different to the one in my car although the engine code and model year is the same, weird

 

also why would it make noise only when i rev it in neutral, no noise if i hold constant rpms, no noise when decelerating, super weird

 

 

 

Edited 23 August, 20214 yr by LightRobin

the tensioner on my car looks like this one, same with the belt, https://skoda.7zap.com/en/cz/fabia/fab/2015-797/9/903-903030/

although thats for the 1.2L model

I don't feel I can help you much from here.  

Looking on the dark side, it could be neither tensioner nor alternator, as you've removed a side load on the crank nose by taking the belt off. 

 

Unfortunately the dark side does need considering in which case anything that reduces the stress there is a good idea so having good sparkplugs to help the engine run well is a good idea, as is reducing the work the alternator does.  This would mean babying the car by not driving it hard, overloading it, lugging in too lower gear or revs and to keep your electric load to lower levels where possible and have the battery in a good state of charge.

 

On the optimistic bright side perhaps it's the alternator making the noise or contributing a lot to it, careful use of something like the stethoscope might help pin this down more.  - ETA: see also my next post

 

One way to see if the tensioner or alternator are making a noise is to bypass them one at a time with a made-up belt but if it breaks or comes off more damage can occur but if the alternator was making that much knocking noise you should be able to tell just grabbing its pully and spinning it and  rocking it, you should feel and/or hear it.  You might also be able to feel or hear get some movement on the pully too.

 

These two items might be damaged independently, separately, together and/or with or without something in the engine, a good interpretation of a scan read might establish this.

 

I'll see if I can find better ideas for tensioner or alternator, in the mean time, this Gates link.  - https://www.gatestechzone.com/en/problem-diagnosis/accessory-drive-system/tensioner-failure-signs

 

And this video is well explained and gives audio to noise. - https://www.youtube.com/watch?v=jVZK7iMTdc8

 

 

Edited 23 August, 20214 yr by nta16
ETA:

I couldn't find a suitable video but was reminded of the much better idea of using a a length of hose, as wide as possible, to hold to your ear to listen for the noise rather than risking cracking your skull or ear with a long screwdriver or stick and a bit of metal on a stethoscope that might also go astray and damage you and stuff in the engine bay.

 

Just a little bit of an update, changed out the belt tensioner today, fixed the rattle but the knock is still there, perhaps I'll try changing just the alternator pulley since the alternator bearings feel smooth and tight

I forgot to mention before to check belt for wear, rubbing and cracking but assume it was OK. 

 

With a new belt tensioner fitted it should be easier to hear if the alternator bearings are noisy with the engine running and careful use of hose.

 

If the alternator bearing feels smooth and tight and you've checked the alternator fixings are tight too then I can't see the alternator pulley effecting anything unless it's loose, in which case (usually?) it can be tighten.

 

Taking above into consideration or action, without see or hearing the knocking, over the internet only, it tends towards the engine knocking noise rather than the alternator as that's more of a grind/squeal/whistle sorts of noise.

 

Edited 30 August, 20214 yr by nta16