VW Golf MK4 130TDI - Air leak when accelerating + grey exhaust smoke | Technical matters | Back Room Forum

Mon 8 Aug 2011 18:00

VW Golf MK4 130TDI - Air leak when accelerating + grey exhaust smoke - turbow

Reg Feb 2002. 131,000 miles. Owned for last 61,000 miles.

About 500 miles ago I became aware of a feint ‘whooshing’ sound when accelerating. This noise has got far more pronounced over the last few days appearing to come from the dash air vents – louder than when the fan is on full blast. Yesterday it was quite obvious that the exhaust gases were a grey colour all the time I was accelerating. I have also noticed a slight drop in economy in the last few days.

I think I have an air leak after the filter with extra fuel being drawn in to compensate (hence the grey smoke) - but where could the leak be? Is it near the turbo? Could it be the turbo itself?

The flexible hose air filter/large diameter alloy tube is OK. The large diameter alloy tube drops behind the engine but where to? Does it connect direct to the turbo? – but how?

On the off-side of the engine compartment a large, squarish plastic tube runs from the front low down, up and over the cam belt housing terminating in a rubber hose/alloy tube. This then connects in to a large diameter alloy housing on top rear of the engine. Removing this rubber/alloy end reveals black, oily gunge on the inside. I’m guessing that this is some sort of oil breather pipe and hopefully doesn’t have anything to do with the passage of air?

A friend has mentioned the Intercooler as a possibility – but other that thinking it may have something to do with the cooling of oil I am rather lost.

Approximately 1500 miles ago the original exhaust was completely replaced along with the cam belt, all filters and oil etc. The guy is on holiday for the rest of August so I can’t take back there.

I would be very grateful of any assistance in homing in on where my problem lies and how best to cure it.

Edited by turbow on 08/08/2011 at 18:01

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Mon 8 Aug 2011 20:12

VW Golf MK4 130TDI - Air leak when accelerating + grey exhaust smoke - unthrottled

Well you're not going to have a leak upstream of the turbo compressor! Follow the intake ducting from the exit of the turbo to the intercooler and through to the intake manifold. Leaks can often be identified by a streak of soot or oil.

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Mon 8 Aug 2011 23:11

VW Golf MK4 130TDI - Air leak when accelerating + grey exhaust smoke - turbow

Many thanks for taking the time to post a response. I take your point that the problem will be down stream of the turbo. I will do as you suggest and then post my findings.

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Sat 13 Aug 2011 17:06

VW Golf MK4 130TDI - Air leak when accelerating + grey exhaust smoke - turbow

Hello unthrottled,

Thankfully, I eventually found the problem. On the Golf MK4 TDI, the intercooler is located tucked away under the near-side headlamp unit. When the cam belt was replaced the mechanic must have to had to remove the stiff large diameter plastic tube (inverted U shape) that runs from the turbo (rear near-side engine) over the top of cam belt cover down to the intercooler. I found the end of the U tube virtually adrift from the interecooler allowing air to be drawn in. Removing the rear of the H/L unit and disconnecting the H/L at the top permit reconnection of the U tube with the large circlip sprung back in to its rightful place. All is fine now!!

Many thanks.

Regards

Edited by turbow on 13/08/2011 at 17:07

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Sat 13 Aug 2011 18:07

VW Golf MK4 130TDI - Air leak when accelerating + grey exhaust smoke - unthrottled

Wonderful news! Thanks for the update which is the most important post on a thread.

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