Leon TDI 150 blow-off valve?

[Scottl]

Hi

Im not sure the TDIs have a dump valve like a petrol turbo, but I've heard they have some kind of valve to vent excess pressure, etc,

Can someone tell me whereabouts it is in the engine bay so I can check it over?

I knew where everything was on my old Impreza but I'm struggling a bit with these vag diesel engines!

Cheers.

 

[Muttley]

There is no need for anything like a dump valve on a turbodiesel, even less for a blow-off valve. No throttle, power output is varied by injection quantity. No other need to vent excess pressure, there is no excess pressure. Boost is controlled by the ECU and turbo vane positioning.

 

[Scottl]

Oh good, I'm still learning the diesel way I guess.

What causes the strange noises when you lift off suddenly then?

I can hear the faint sound of what we used to call 'impeller stall' but there also sounds like a sucking noise, possibly coming from the airbox (I did post a similar thread before but I like to try and understand what my car is doing).

 

[johntheboy]

I still wonder that myself what the noises are.

 

[Scottl]

I eventually found the source of the sucking type noise - The air box is resonating against something in the engine bay (strange)!

I'm thinking the rubber bushings may have come loose or something so will try and re-secure/dampen it this weekend.

 

[johntheboy]

Sorry to sound stupid but how do you mean resonating against something in the engine bay?

 

[black04ctdi]

Most likely the battery cover in front of the airbox. Mine used to vibrate all the time when idling and up to about 1200-1500 revs, when I bought it, the previous owner even had the Stealer try and fix it, which they clearly couldn't! I dremmeled the back edge of the battery cover where it touched, fixed it.

Couple of weeks later (after having to jump start my missus' poop Polo) I found that the removeable part of the battery cover was being pushed backwards because the padded sleeve type thing around the battery was scrunched up and pushed down at the front. Managed to pull the sleeve up while fitting the cover back on and now its waaay away from the airbox!

 

[Scottl]

Thanks black04ctdi I will try that.

In reply to johntheboy, I got my girlfirend to hold the revs at about 1200 (where it seemed to sound constant on the way home) and pushed down on the airbox. As I pushed down she said the noise seemed to go, when I let go it came back.

I know it sounds strange but the airbox must be vibrating at certain frequencies to cause the weird noises.

 

[Silence]

Thanks black04ctdi I will try that.

In reply to johntheboy, I got my girlfirend to hold the revs at about 1200 (where it seemed to sound constant on the way home) and pushed down on the airbox. As I pushed down she said the noise seemed to go, when I let go it came back.

I know it sounds strange but the airbox must be vibrating at certain frequencies to cause the weird noises.

Hi Scottl,

Just wondering whether you managed to fix the suction-type noise? Was it the battery cover vibrating against the air box?

 

[Scottl]

Hi

It turned out to be that one of the airbox mountings had popped the rubber bushing inside out (the one tucked next to the battery cover) meaning it was sitting lower at a slight angle.

I managed to removed the bolt and push the rubber in the mounting back the right way - the airbox seems to sit fine now and no more weird noises.

 

[Silence]

Hi

It turned out to be that one of the airbox mountings had popped the rubber bushing inside out (the one tucked next to the battery cover) meaning it was sitting lower at a slight angle.

I managed to removed the bolt and push the rubber in the mounting back the right way - the airbox seems to sit fine now and no more weird noises.

As I’m a complete newb when it comes to these things, would you please be kind enough to post a picture of the said rubber bushing and how you removed the bolt? My car has been making the same noise for a while and would much rather fix it myself (if it is an easy fix) rather than taking it to the dealers.

I appreciate your help mate!

V