strange noise over 4700 rpm.

[arjunior45]

Just after having fixed the fuel leak at the fourth injector, raising the fuel pressure and replacing a couple of broken water tubes, when the engine is above the 70 - 75 degrees {not when is colder} I hear a strange noise, something like fsssssss, when I pass the 4700 rpm in all gears and this noise is getting stronger as the revolution goes up! Seams that is coming from the right side of the car but I can't locate it.

Any suggestions?

Nick

[Steve Webb]

Is that the right hand side when you are sitting in the car, (cambelt end)?

Is it losing any water?

Have you noticed any lack/increase of power?

[arjunior45]

Is that the right hand side when you are sitting in the car, (cambelt end)?

Is it losing any water?

Have you noticed any lack/increase of power?

yes, it is from the right hand side sitting in the car {driver's side for UK, passenger's side rest of Europe}.

There was a water leak before but I did not notice any after changing the tubes from the expansion tank.

I think I notice a minor lack of power at high revs, but I can't be that sure for I use a 0.65 - 0.7 bar boost map {not the oem eprom} all the time. But I believe that the car hesitate a little bit more than the first day {after fixing the leaks - tubes when I did not herd that noise} at high revs. The second day the noise started and maybe the lack of power.

I though it might be an air-boost leak but I believe in that case I should hear the noise around the revs with max boost {3200 - 3500} and not at the revs {4700 onwards} when the boost starts to lower.

Nick

[AlfaJack]

Could it be one of the rubber bits that join the two parts of the inlet manifold is split? Maybe disturbed from your previous work...

[RMB-Racing]

You got to check all your pressure tubes, hoses etc. for any leaks.

And I mean them all!

The smallest of the smallest rip in a pressure hose, can make your loose power.

What about your blow off vent? Have you checked this one?

It could be malfunction...?!

[arjunior45]

Could it be one of the rubber bits that join the two parts of the inlet manifold is split? Maybe disturbed from your previous work...

replaced them with new one {from Kappa turbo I believe} when I took off the inlet manifold {for a second time}. The old one were quite hard and that's the reason I've replaced them.
Though the noise was - is still there.

Nick

[arjunior45]

You got to check all your pressure tubes, hoses etc. for any leaks.

And I mean them all!

The smallest of the smallest rip in a pressure hose, can make your loose power.

What about your blow off vent? Have you checked this one?

It could be malfunction...?!

I was afraid of that {checking them all} for the axes to all is not that easy, mostly those in the back - under the inlet manifold.

What is the 'blow off vent'? Where is it located?

Nick

[Brul(tm)]

What is the 'blow off vent'? Where is it located?

This a valve which releases the build up pressure back into the air inlet or into the open air "whooossssshhhh"

You can find this valve in the front of the car in the hose from the airbox next to the left front headlight unit.

Greetings,
Marc

[arjunior45]

This a valve which releases the build up pressure back into the air inlet or into the open air "whooossssshhhh"

You can find this valve in the front of the car in the hose from the airbox next to the left front headlight unit.

Greetings,
Marc

you mean the "Pierburg"?

Nick

[AlfaJack]

I think he means the dump valve.

[arjunior45]

I think he means the dump valve.

is the dump valve the one called 'stall prevention valve' in the workshop manual?

is this the tube {see picture} that is connected to this valve? I mean the tube under the 'vacuum tube' for the fuel pressure regulator?

Nick

[AlfaJack]

is the dump valve the one called 'stall prevention valve' in the workshop manual?

is this the tube {see picture} that is connected to this valve? I mean the tube under the 'vacuum tube' for the fuel pressure regulator?

Nick

Turbo stall prevention valve - thats the one. If its worn, it will leak.

From memory I am not sure if that is the hose that connects to it but its one of those small bore types. Can check tomorrow though.

[arjunior45]

Turbo stall prevention valve - thats the one. If its worn, it will leak.

From memory I am not sure if that is the hose that connects to it but its one of those small bore types. Can check tomorrow though.

well, I'm almost certain that this is the tube-hose for the dump valve.
At the begging, the hose that connects the inlet manifold to this valve was interrupted. After restoring the connection {see picture}, the noise started!

Well, how do I check this 'blow off vent' - dump valve - turbo stall prevention valve? I did not find anything in the manual.
If this valve is worn, is there anything I can do for that or do I have to replace the valve?

Nick

[arjunior45]

today is a raining day and,
I hear NO NOISE AT ALL.
I went up to the rev limits for many times and still no noise. I believe my 'problem' has nothing to do with the tubes - hoses and certainly is temperature related!!!
Need to check the dump valve yet and thinking to replace it. But I need a sunny day!

Nick

[arjunior45]

today is a sunny day at 22 degrees and I was thinking - hoping to hear the strange noise so that to locate the problem. Took the car for a spin, following an RS4 and a Golf GTI, until we 'met' a police car but still NO STRANGE NOISE at all.
I'm getting angry with it. The only thing I've done was to disconnect the wires from the idle valve and replace the plastic cover of them.

Nick