Worrying noise under boost/acceleration

[icyd]

recently, my 1.8t auto started making this noise, i'm not quite able to describe it perfectly but my best is gluk gluk gluk. when even my wife is able to notice it, surely it's there. whatever it is, the noise is pulsating at constant rate only under heavy/partly heavy acceleration. no noise at cruising speed. no noticable loss of power, or probably that's because i always back up the throttle a bit from fearing something might burst.i don't think that's highly likely but i prepared for the worst.the noise goes away when i do that.

 

to help with diagnosing here's a list of info;

 

-just did the coolant flange change (hoses were disconnected but inspected all seems to hv been put back in nice and tight)

-replaced two cracked hoses on top of the turbo (i think they're breather hose or water hose of some sort) with generic non OEM hoses

-topped up with g13 coolant instead of g12 (the only one i could find during that time frame)

-no CEL

-noise absent in 1st gear even when pushed hard

-fuel consumption normal -temperature rock solid at 90 deg

-differential is seeping oil,not seriously leaking tho

-air filter hasn't been changed since the last 2 service intervals (1 year)

-timing belt and water pump done at 150k km, now at 180k km

 

i know im shooting at random here but i have yet to find time to send it for proper inspection so i guess these details might help u to help me and.always reassuring to have a heads up.

Edited 9 June, 2015 by icyd

[KenONeill]

Reassurance on one point - G13 has replaced G12, so it really shouldn't be that.

 

Query - is the noise related to road speed or engine speed?

[icyd]

thanks for that.

 

the noise is related to engine speed, and load.light throttle doesn't produce that noise.seems something to do with turbo, air gong in.usual symptoms i found on the net related to N75, 710N valve, coil, they don't match with what im seeing with my car,as far as my observation skill is concerned

[KenONeill]

That makes me think of broken pipework or a failing control valve (N75, 710N etc).

 

So as being free, I'd start by manually examining every air pipe I can find, and I mean manually. Some of them can fail in points that you can't see, and the externally fabric armoured ones can fail internally and feel soft but look ok when they do.

[icyd]

i'll start off by cleaning the airfilter.my logic says since it only happens when the turbo kicks in, thus huge increase of demand for air more than what can pass thru the clogged filter hence weird stuff happens.it's about time anyway.

[jimbof]

I had something similar to this after gearbox rebuild, and so was very worried.

It was a clunk clunk clunk (always 2,3, or 4 times during moderate acceleration.)

Took it back to gearbox place, no joy.  Swapped driveshaft, no improvement.  Took it to another independent who noticed exhaust alignment was out and knocking during acceleration.  Exhaust had been disconnected by garage to get the autobox out.

[jimbof]

Video of my noise (you can just hear it around 5 secs in)

[KenONeill]

i'll start off by cleaning the airfilter.my logic says since it only happens when the turbo kicks in, thus huge increase of demand for air more than what can pass thru the clogged filter hence weird stuff happens.it's about time anyway.

 

If you're near a road you can do an acceleration run on, it won't do damage to do one or 2 runs with no filter in the box.

I had something similar to this after gearbox rebuild, and so was very worried.

It was a clunk clunk clunk (always 2,3, or 4 times during moderate acceleration.)

Took it back to gearbox place, no joy.  Swapped driveshaft, no improvement.  Took it to another independent who noticed exhaust alignment was out and knocking during acceleration.  Exhaust had been disconnected by garage to get the autobox out.

This is possible, but the OP's description doesn't sound much like any misaligned exhaust I've heard.

To check this, go under the car and look for very clean patches on the system, and on the bodywork near it.

[icyd]

KenONeill was right. that's not the kind of noise im having.i have a strong feeling that it has direct effect from the turbo spooling

[KenONeill]

If you're suspecting it's related to the turbo, there's a couple of things you could try but they're both at least potentially messy.

 

1) Disconnect the lower of the 2 pipes from the intercooler, and see if oil runs out. If it does, that could solve the problem.

 

2) If (1) didn't work, you need to check the turbo feed and return pipes, and check the oil pressure properly (gauge rather than idiot light).

[icyd]

hi all,reporting back from the garage.did nothing to it apart from topping up differential fluid and replacing air filter.as i suspected the noise is still there,except louder that now im able to properly discern the noise pattern.or maybe just because i had the radio off and no kids.i was mistaken.it was not constant.it follows the wheel speed.and it's most likely mechanical.please see the recordings;

 

https://youtu.be/C5tzI9l7BHs

 

https://youtu.be/1L84nnOzGkY

 

err..embedding youtube,am i doing it right?

 

my mechanic said it's likely the gearbox final drive gear.i believed him.but on the drive back,my suspicion arose.that may not be the case judging from the noise that's seem to be originating from the right side instead of the middle.and no clunking during start stop traffic jam.i figured if the final drive gear is knackered,that's when the noise should appear because that's the initial point the engine torque gets transferred,and that's a hell of a stress to a bad gear.or maybe im just biased since i really don't want to part the gearbox