"Funny"/"worrying" engine-related noise - turbo, aircon or what?

[jeallen01]

A couple of weeks ago we went out for the day and drove about 50 miles - most of which was "poodling" along in Bank Holiday traffic, but the last couple of miles was somewhat quicker (but definitely NOT "flat out") down some side roads.

 

Then, as we slowed to go through a village, there was this loud engine-revs related noise from under the bonnet - slowed right down immediately, suspecting ANOTHER turbo failure, and stopped for a couple of minutes to decide what to do. Then decided to back-track a couple of hundred yards to a pub to call the recovery service, and wait - still some noise at that point, but no smoke or other "bad" signs.

 

However, when the recovery truck arrived about an hour later, the noise had "gone away" and so, in the end, we got the recovery driver to follow us for a few miles  - and still no further "noise", so we drove home very gently along main roads with, again, no "noise" etc, even for the last few miles when I experimentally speeded up to about 70mph on some dual carriageway and then backed off again at the next exit.

 

Drove gently around for a few days and still no noise, and so gradually increased the revs until, one warm day last week, I thought I was beginning to hear something when I came to a halt with the engine running - not a turbo whine but more of a clattering which disappeared when the revs were raised above about 1200, and which did not come back again after the engine was switched off and then back on again sometime later.

 

On both occasions when the "noise" occurred the weather was warmish  (18-22C) and the aircon was being used (quite deliberately on the 2nd occasion as I was trying to find out if the noise would be aircon-related..

NB:

- aircon compressor was replaced a couple of years ago and it's definitely still working because you do get cold air when you ask for it

- no sign of any drop (or rise) in the engine oil or coolant levels, and no white/black smoke from the exhaust since the "noise" first occurred.

- pretty sure noise is not engine cooling fan-related as it does not appear to be coming from the very front of the engine bay.

 

So, per the Topic Title, turbo, aircon or what?

[jeallen01]

_{Sorry to have to have to ask again - but any ideas?}

 

_{Thanks in advance.}

 

_John

[Nikonite]

Something catching a fan? sorry couldn't resist the font change   

[jeallen01]

Something catching a fan? sorry couldn't resist the font change   

Thanks but I would have thought it would have happened at other times because most of my current driving is in town and the engine does get quite warm - however, maybe I can bypass the rad fan switch and get that fan running to check.

 

Font size issue - I tried to make it larger but couldn't do it that time - hope it is better this time

[Nikonite]

Any chance something was caught under the car? My old volvo dead a loose engine cover below car that gave me quite a fright once. Hard to think what would create such a noise Yet produce no symptoms.

[jeallen01]

Any chance something was caught under the car? My old volvo dead a loose engine cover below car that gave me quite a fright once. Hard to think what would create such a noise Yet produce no symptoms.

Good idea, but don't think so (will check anyway).

[jeallen01]

Woke up far too early this morning as I was supposed to be going to Portsmouth but then lay awake worrying about "the noise" on a long journey (haven't done many of those lately) - and then I had a thought: could it be from a worn water pump that only "rattles" when the engine gets really warm?

 

You used to get this sort of noise from the pumps on older (1960s/70s)  cars as the pumps got worn but I have never heard it from more modern ones because (I assume) manufacturing standards have improved a lot.

 

However, as I have never heard a VAG pump "rattle" I don't know if they do, and, if so, what they actually sound like - does anyone else?

 

Or else could it be coming from the cam belt tensioning rollers?

 

PS: decided not to go to Portsmouth for obvious reasons!

[whitep]

I had a noise like htis, it was the fan clipping the air intake at the top of the radiator. I was really worried, but it was nothing.

[faradaycage]

Woke up far too early this morning as I was supposed to be going to Portsmouth but then lay awake worrying about "the noise" on a long journey (haven't done many of those lately) - and then I had a thought: could it be from a worn water pump that only "rattles" when the engine gets really warm?

 

You used to get this sort of noise from the pumps on older (1960s/70s)  cars as the pumps got worn but I have never heard it from more modern ones because (I assume) manufacturing standards have improved a lot.

 

However, as I have never heard a VAG pump "rattle" I don't know if they do, and, if so, what they actually sound like - does anyone else?

 

Or else could it be coming from the cam belt tensioning rollers?

 

PS: decided not to go to Portsmouth for obvious reasons!

If you.ve reached the stage when you are actually cancelling journeys it really is time to get the opinion of a good,local VAG specialist,I'd say.Just for peace of mind.

Edited 28 April, 2015 by faradaycage

[jeallen01]

If you.ve reached the stage when you are actually cancelling journeys it really is time to get the opinion of a good,local VAG specialist,I'd say.Just for peace of mind.

Problem with that is that the noise is so very very intermittent that it will inevitably not happen if I do!

[faradaycage]

Problem with that is that the noise is so very very intermittent that it will inevitably not happen if I do!

I understand what you're saying,but just describe the symptoms to them,they may have come across the problem before and be able to offer you a solution that will put your mind at ease.As things stand at the moment you don't trust it on long journeys and thats not a fun place to be,nagging doubts ,long term don't equate to satisfied,happy ownership.

[jeallen01]

FWIW, just been out for a short run and then checked the fans (which were not yet running because the engine was not warm enough) behind the rad - spun and wiggled both of them with no sign of either being likely to touch anything else, so probably not them.

 

Also, as I remember, the noise was coming from further back in the engine compartment, on the driver's side.

Edited 28 April, 2015 by jeallen01

[pikpilot]

Not sure its the same on a Mk 2 but on a Mk 1 I would have said it could be the alternator free-wheel and the tensioner for its drive belt? Failure of the freewheel can also cause the tensioner to fail so replace both if necessary.

Edited 28 April, 2015 by pikpilot

[jeallen01]

Have you checked the alternator free-wheel and the tensioner for its drive belt? Failure of the freewheel can also cause the tensioner to fail so replace both if necessary.

Thanks, not heard of that one, so not yet checked

[whitep]

Oh yes, EVERY SINGLE VAG car I know (about 8 in the family) have had an alternator go to one extent or another every 120k miles. Almost on the dot. So much so I generally clear some time to do it when I know the car is approaching 120k.

[jeallen01]

Oh yes, EVERY SINGLE VAG car I know (about 8 in the family) have had an alternator go to one extent or another every 120k miles. Almost on the dot. So much so I generally clear some time to do it when I know the car is approaching 120k.

This one has done 112k miles, so that could be right.

 

The wife's Mk IV 2l petrol has done 103k, so I will keep an eye/ear out for that happening in the future

 

OTOH, my old Mk IV Golf TDI did over 150k before it happened (to my neighbour who now has the car!  )

[whitep]

150 isnt that far away, but a couple of years driving. I used to send it in to a garage to have it done till i needed one done in an emergency and realised how easy it is.... no way woul dI pay anyone to do it now. Euro car parts every time. Think I paid £80 for a Bosch one last time, after I returned the old one, which actually wasnt even from a VAG car, it was just an old one I had kicking around! Ha Ha.

[jeallen01]

150 isnt that far away, but a couple of years driving. I used to send it in to a garage to have it done till i needed one done in an emergency and realised how easy it is.... no way woul dI pay anyone to do it now. Euro car parts every time. Think I paid £80 for a Bosch one last time, after I returned the old one, which actually wasnt even from a VAG car, it was just an old one I had kicking around! Ha Ha.

They are a BIT (!) more expensive at ECP for this car nowadays - quoting about £250 for the Bosch version today. Other makes are cheaper, but still £150+ !!!!!

[whitep]

Yeah I think the 250 is pre exchange. It was only 2 years ago when I paid that for a 1.9 MK1 TBH, not a MK2, but I think they are all very similar.

[jeallen01]

If you.ve reached the stage when you are actually cancelling journeys it really is time to get the opinion of a good,local VAG specialist,I'd say.Just for peace of mind.

After a fast 40 mile thrash down/up/down/up the M4 from J3 to J6, and then a gentle tootle around the area, but no "noises" , I went to see my local VAG specialist.

 

Looks like the possibilities are the water pump or the alternator and/or associated components (but not the turbo, T.G.!), so I will have to wait and see as to when/if the "noise" returns!

[faradaycage]

After a fast 40 mile thrash down/up/down/up the M4 from J3 to J6, and then a gentle tootle around the area, but no "noises" , I went to see my local VAG specialist.

 

Looks like the possibilities are the water pump or the alternator and/or associated components (but not the turbo, T.G.!), so I will have to wait and see as to when/if the "noise" returns!

I know how you feel,its maddening,but at least as you say its not the turbo.

[jeallen01]

UPDATE & GROAN!

 

Having left the car where it was overnight, I went to start it this morning - but it won't!

 

Engine turns over quickly (new battery fitted recently), all the initial warning lights extinguish, but makes absolutely no effort to fire on even 1 cylinder (usually starts quickly and evenly).

 

Ran a Vagcom check - no engine error codes, but, possibly significantly, no response from the Diesel ECU.

 

Only other fault indication was that the green oil can pressure warning light went off after a few turns of the engine, but continued cranking brought up the amber oil can - I assume this means low oil level, but dipstick level is fine.

 

Could the problem be a failure of the diesel lift pump, or something associated with it, and could that have been from where the "noise" came.?

[jeallen01]

Update again!

 

Was something to do with the fuel pump system! :clap:

 

Quick search on Google lead to some threads on the vwaudi forum pointing to possible fuse-related issues for the diesel pump - pulled all the fuses, one by one, in the fuse box in the cabin -> no blown fuses -> reseated them all.

 

Tried to start again, and after a prolonged period of turning the engine over, it began to show signs of wanting to fire, so carried on - and it then fired on all four cylinders! Turned engine off and then on again several times, and it fired up immediately each time.

 

I assume it was a little bit of corrosion on the blades of the relevant fuse, and so either the tank pump or the diesel ECU was not working - but does anyone know exactly which one that is because I can't be sure?

 

Still not solved the noise problem though!

Edited 30 April, 2015 by jeallen01

[jeallen01]

 

I assume it was a little bit of corrosion on the blades of the relevant fuse, and so either the tank pump or the diesel ECU was not working - but does anyone know exactly which one that is because I can't be sure?

This Dodo did not RTFM, or at least the right manual (i.e. the "Owners Manual", no less!), and it was one of the two that I had suspected:

F1 is for the diagnostic socket, engine ECU and pump tank - the diagnostic socket and ECU were working, so not that one.

F27 is for the fuel pump relay and injection valves - so must have been that one. Will put a new one in (with some contact cleaner) tomorrow to try to avoid this happening again!

[wonkyewok]

maybe not the same thing...

I've got a 1.4 tsi petrol. it's just started sounding like a clattery diesel but a bit quieter between 850 and 950 rpm. smooth as normal above that. When fully warm the noise almost goes away.