HUGE vacuum leak Help! :(

[a3rider]

Hey Guys, few weeks ago i went to check the oil noticed that my engine is sucking a lot of air, when i took the engine cap of the engine would almost die/turn off and would shake.

Ive looked around and needed to know has anyone else experienced this, had the vagcom checked it and returned nothing. ANY Advice would be appreciated.

Been driving for weeks now accelerate is terrible at low revs ive been getting around 190km half a tank is that normal?

 

[warren_S5]

Engine size / fuel type / age / mileage??????????

Give us a clue!

 

[a3rider]

A3 2.0T quattro 2006 around 72,000 km Petrol of course.

 

[Sarah's A3]

Have you checked all the levels and seals for leaks or split pipes??

 

[a3rider]

yeah i have, cant see anything that will cause such a vacuum leak.

 

[warren_S5]

Next step would be to check all your hoses. Have you tightened any jubilee clips recently that may have cut into pipe work? (easily done).

Check the TIP as sometimes oil gets between this pipe and the turbo and can cause it to rise off it's flange which may compromise the seal to the turbo housing. Might also be worth checking inter cooler hoses too. Appreciate DV is a pain to check on 2.0T, but have you checked it recently?

Would a knackered PCV cause vacuum issues??? Not sure, but if you try the others and find nothing try the Jonny C PCV delete to see if it creates any improvement for not much money.

Would be useful if you could get someone to VCDS scan the car to make sure it's nothing less obvious.

Cheers
W

 

[Lewis583]

Sounds like it could be PCV valve in my opinion. With a knackered pcv valve, at idle the inlet would be creating a vacuum in the crankcase and when you take the oil cap off it would allow unmetered air to enter the system possibly causing the unstable idle.

 

[a3rider]

the thing is the idling remains fine when i take the engine cap off./

 

[Lewis583]

You said when you take the cap off the engine almost turns off?

 

[a3rider]

yeah it does, but when i go and check the bar sits at 1000 rmps idling normally :S

 

[Lewis583]

It will idle normally with the oil cap on because the oil cap in effect seals the crankcase therefore stopping the unmetered air entering the system, whereas when you take the oil cap off there is nothing stopping the engine from sucking unmetered air through open oil filler through the crankcase and then through the pcv valve.

 

[a3rider]

idling remains at 1000 rmps with cap off or on i just checked it.

 

[warren_S5]

Hey Guys, few weeks ago i went to check the oil noticed that my engine is sucking a lot of air, when i took the engine cap of the engine would almost die/turn off and would shake.

So what you are saying is when you take the cap off it almost dies and shakes, but then continues to run at 1,000rpm.

You're going to get a pressure change within the system if you just take the cap off whilst it's running, so I'd expect to see a fluctuation in the running of the engine.

120 miles from half a tank of fuel does seem on the low side, but not unachievable if your caning it about the place.

To be honest these kind of issues are very hard to determine on a forum without seeing the car in the flesh, there are so many variables that can throw things out it's never as simple as a 'magic identifiable fix'

 

[a3rider]

So what you are saying is when you take the cap off it almost dies and shakes, but then continues to run at 1,000rpm.

You're going to get a pressure change within the system if you just take the cap off whilst it's running, so I'd expect to see a fluctuation in the running of the engine.

120 miles from half a tank of fuel does seem on the low side, but not unachievable if your caning it about the place.

To be honest these kind of issues are very hard to determine on a forum without seeing the car in the flesh, there are so many variables that can throw things out it's never as simple as a 'magic identifiable fix'

yeah it remains constant at the 1000 rpms, if it was idling problem i would know how to fix it, but this isnt something ive experienced before so any advice or any past experience would be appreciated, And the thing is i've been driving to the best of my ability changing gears at 3000rpms and super good driving and still i get crazy consumption. but thanx. i guess ill check everything mentioned tomorrow when i have time