Loud blowing sound from under bonnet

[supersyz]

I'm noticing a blowing sounds from under the bonnet when I'm hard on the power, I took it to my garage to get it checked out.
They have come back to me saying they think its my air pump and have recommended I put my standard air box back on.

I only ever put the cone filter on years ago when I went stage 2. Would it all of a sudden be making this sound years later?

Any advice would be greatly appreciated.

 

[Phillc]

I am assuming you have a Cupra, the secondary air pump ( can only think thats what they ment) only comes on when you start from cold so doubt its that

 

[supersyz]

Yes its the cupra, I hear that sound from cold and it isn't that. I didn't have much confidence in what they said. Its only recently been making this blowing sound.

I thought it was a blowing gasket or something but they said they checked all that's and its fine.

Thnx for your reply!

 

[ash_453]

not a vacuum pipe just behind the engine above the dump valve is it? they can rub through where the metal clip is on them, unless thats just lcr not sure

 

[Muttley]

Boost hose split or leaking at a joint.

 

[supersyz]

Coincidently I had a 5 piece hose kit and the breather hose replaced today also. That's what I had the car booked in for initially and just got them to check for the noise while they where there.


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Those where the hoses I had fitted today but the sound is still the same, is there another I should check?

Thnk so much for your replies.

 

[Muttley]

Listings ended, items no longer available. You need to check every hose and joint between the turbocharger and the inlet manifold. You could also check the intercooler - they have been known to spring a leak, although it is fairly unusual.


But just listening at the open bonnet while someone revs the engine for you should give a clue as to the precise location of the noise. Just don't lean into the engine bay unless you have nothing dangling at all: hair, jewellery, shirt-sleeves, anything.

 

[supersyz]

Thnx buddy, you can scroll down and still see the items but I think you have given me enough info to hunt myself.

 

[rsmith]

Just get a leak test if you think a pipe is blowing, you won't hear much with someone just revving the engine as there is no load generated and the turbo won't great boost.

 

[Seatmann]

The turbo will still boost even when revving in neutral bud, if it's a burst pipe it kinda sounds a bit like fiiisshhhh when you rev reasonably hard. You might also see an oily patch on one of the boost pipes or around a connection which would indicate a leak or burst.

 

[rsmith]

The turbo will still boost even when revving in neutral bud, if it's a burst pipe it kinda sounds a bit like fiiisshhhh when you rev reasonably hard. You might also see an oily patch on one of the boost pipes or around a connection which would indicate a leak or burst.

No, it will barely create any positive boost more over if there is a leak it will not generate enough to highligt it unless it's a huge tear, Check your boost gauge next time your revving in neutral, it will barely get into positive pressure, even better check your wastegate duty cycles next time....

 

[Seatmann]

It does if you rev it hard enough lol, me and a mate found his doing this, made a big farty fish sound.

 

[rsmith]

It does if you rev it hard enough lol, me and a mate found his doing this, made a big farty fish sound.

Sure, if you say so.

 

[Seatmann]

No need for sarcasim, we found the leak on a friends fiat td this way, if the leak is big enough then it works because the turbo still spools up when you rev it reasonably hard.

 

[rsmith]

No need for sarcasim, we found the leak on a friends fiat td this way, if the leak is big enough then it works because the turbo still spools up when you rev it reasonably hard.

Do you know how a turbo works, it will spin on revs but will not build boost, there needs to be engine load.If you are generating above atmospheric boost, enough to find a leak in neutral then there is something up and fair play to you if you can hear a big leak over an engine revving at 7k with your head in the engine bay.

I am just pointing out that its not a realiable test and turbo don't generate enough boost at idle for the test.

 

[Seatmann]

Ok so it's not scientific but the turbo has to produce some sort of boost in order to match the fuel otherwise surely it'll smoke. How else can it up the combustion pressure to the required amount?
I certainly don't suggest revving to 7000 either, I'm talking a quick rev to about 4000 then off with the foot and I'm not arguing or saying I'm right and you're wrong, I love my tdi and like learning more as I go but when revving a friends fiat turbo diesel it did make a big fiiisshhh sort of noise through a burst in a pipe, it was an 06 plate.

 

[Random1989]

i've got a boost gauge in my car and rsmith is right it only just gets to 0bar at full revs in neutral but on the road i get 1.5bar

 

[supersyz]

Turns out my exhaust was blowing at a joint, I got it repaired by the peole who made it and its allot better.

The turbo sound still doesn't sound as smooth as it used to but then I could be just listening too close. I was advised again to remove my cone filter and put my standard box back on with a panel filter.

 

[rk696]

That's good advice.

Oh, and rsmith, Seatmann has a diesel, which will spool a lot easier compared to a petrol engine (no throttle plate to restirct airflow into cylinders)

And when you put your foot down when revving it, you will get 100% engine load for a second until it redlines.

 

[supersyz]

Will a standard box be OK as I only fitted the cone as it was recommended for my stage 2 from revo.