MK5 GTI 'hissing' noise on idle

[mk5gtibwa]

Hey everyone!

Recently bought a MK5 GTI engine code BWA with 120k on the clock. Noticed a hissing sound like theres a vaccum leak somewhere. It occurs at regular intervals every few seconds. I can't see anything but was wondering what you guys thought, you do have to listen closely to hear it. I've attached the youtube link of the video I recorded.

I did a scan with Carista obd device and there were some error codes that popped up that could be related:
P0441 - Evaporative (EVAP) Emission Control System, Incorrect Flow
P0234 - Boost Pressure Regulation, Limit Exceeded (Overboost Condition)
P0444 - Evaporative (EVAP) Emission Control System Purge Control Valve, Circuit
P0033 - Turbo Charger Bypass Valve (N249), Control Circuit
P0243 - Solenoid Valve (A) for Boost Pressure Control (N75), Open / Short Circuit to Ground

Would appreciate any help!

[LC5F]

The most serious issue you have is a leak in the evap or boost system - lots of places it could be - diverter valve, boost hoes leak, evap pipework, cam cover gasket, etc.

The P0243 is N75 valve & P0441 is the carbon canister - these are lesser issues than above, on mine these would only flag up once a month. Of the 2 items, one is not working, generating the 2 faults - easy DIY fixes, try a canister, cheap ones from jungle web site or ebay are fine, if the faults are still there replace the valve - Bosch make these for VW, just get a genuine Bosch replacement.

Couldn't hear anything in the vid, but the drive belt tensioner is moving in and out quite a bit as if something is loading up the belt every other second - normally these will sit steady. This could be the tensioner, AC or Alternator pully binding up.

[mk5gtibwa]

The most serious issue you have is a leak in the evap or boost system - lots of places it could be - diverter valve, boost hoes leak, evap pipework, cam cover gasket, etc.

The P0243 is N75 valve & P0441 is the carbon canister - these are lesser issues than above, on mine these would only flag up once a month. Of the 2 items, one is not working, generating the 2 faults - easy DIY fixes, try a canister, cheap ones from jungle web site or ebay are fine, if the faults are still there replace the valve - Bosch make these for VW, just get a genuine Bosch replacement.

Couldn't hear anything in the vid, but the drive belt tensioner is moving in and out quite a bit as if something is loading up the belt every other second - normally these will sit steady. This could be the tensioner, AC or Alternator pully binding up.

Thanks for your reply, I thought the P0441 would either be the N80 purge valve or the carbon canister, I am getting VCDS soon so I will hopefully be able to test the N80 and then I can either replace that or the carbon canister, I'm hoping its the N80 as that's only around £15 for a Bosch one.
Yeah, I agree the P0243 is probably a bad N75 solenoid, I have ordered one to replace it anyway as I have heard they do go bad on MK5's. I have also bought a new Diverter valve rev G as the one at the moment is a rev D and hasnt been replaced since 2016 so it could be faulty and as they're a common MK5 issue, I thought might aswell. I will let u know how I get on after replacing these items (if you're interested that is  ) 

To hear the 'hissing' sound you do have to listen closely, as in the phone next to your ear kinda vibe but I admit it is hard to hear. In terms of the drive belt tensioner, I'm not sure what's causing that.

There is a noise from the AC but that happens as soon as you turn the ignition without the engine on and stays on when the engine is on but since the belts not moving when only the ignition is on and not the engine, it can't be that causing the belt issue. However, I have attached a youtube vid of the AC noise in case you wanted to see it anyway. I think its a broken actuator motor as I have received an error code pop up for it previously: 01810 - Actuating Motor for Temperature Flap: Right (V159)

Link to the AC noise: