Hissing noise after engine off

[shaguar]

Hi Everyone,

Had a strange problem start yesterday after dropping off for the VW Golf MKVI 118tsi for its 60K service.

After the car stops and I take the keys out of the ignition.....an intermittent, controlled HISS noise comes from the engine bay that then stops after the fans stop.Total time of hissing = 10 seconds with 4 hiss

Anyone know:

1. If its normal?
2. Should I take back to service?

Thanks in advance

[Ryan_R]

How strange - mine has been doing the same thing ever since I got the car back from the DSG recall. Not the normal cool-down hiss, but a louder, intermittent one as you describe, more noticeable when the car was warmer than usual. Sharp short bursts every second for about 12 seconds last time I checked.

That said I haven't really noticed it this week...

[shaguar]

Yes! That's the noise. I only just got it back from the service where they changed the DSG too. Found a series of hoses that weren't there before? Attached a pic. Thoughts?

How strange - mine has been doing the same thing ever since I got the car back from the DSG recall. Not the normal cool-down hiss, but a louder, intermittent one as you describe, more noticeable when the car was warmer than usual. Sharp short bursts every second for about 12 seconds last time I checked.

That said I haven't really noticed it this week...

[Ryan_R]

Since your car was more recently at the dealer, give them a call and see what they can tell you... I'd be interested to find out.

Which hose(s) exactly do you think are new? (Assuming they didn't install the Forge CAI)

[shaguar]

LOL no they didnt install the Forge.

The hoses that are new are the ones running over the top of the CAI to the engine and the hose underneath the CAI.

Called service now and they said there shouldn't be a noise at all. See what they say when I take it in tommorow!

Just weird how it wasn't there before the service but is there now....

I'm just glad it wasn't a snake hiding in my engine for warmth lol

[Ryan_R]

That hose isn't new per-se - I've always had it. Perhaps it was obscured earlier or maybe even connected elsewhere due to the CAI.
I think it's the pressurized air-intake for the supercharger.

[buzuki]

I assure you those hoses arent new, they are your radiator hoses . . .

[AndrewBurns]

My new Polo GTI does this also, actually if I remember correctly my old 07 camry did it as well. I'm pretty sure it's normal, I think it's actually coming from the airconditioner system (quick google seems to confirm this is a plausible reason).

[grtuned]

7 speed mechatronics will activate a pump to prime the fluid you sure this is not the noise? It sits directly underneath the picture you posted.

[kjh]

My sister's 118TSI has done this same hissing noise since the DSG recall check. Been back to the dealer a couple of times since and they say 'normal operation'... I don't think they are hearing the hissing noise over the normal cooling fan. I have been told they aren't allowed to drive the vehicles enough to get the warmer! The hissing noise is more noticeable as mentioned above - warmer than usual!

[Ryan_R]

I noticed a 103TSI (Mk7) making the same intermittent hissing noise when it was turned off the other week - so it must just be a software update that we've got.

[manny76]

Could be a vacuum leak. I had this on the missus' mk7 gti..... coupled with this the engine check light came on. It was the PCV valve......

Engine light came on due to ECU not being able to compensate for such a vacuum leak at idle.

Engine eventually began idling up to 2k then drop down to 1k.

Its possible that a technician has bumped a vacuum line off. Also check the engine oil dipstick. If the top "o" ring is worn it will also leak vacuum and cause a hissing noise.

Good luck.



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[tonymy01]

Manny, this thread is about engine not running= no vacuum. Only place with vacuum after engine stops is in the brake booster. You can confirm the booster check valve isn't leaking by pressing your foot on the brake before starting and listening for a low sound of air. Pump the pedal a couple of times and you will feel it becomes solid rather than softish(from the stored vacuum boost running out).

But yes,a vacuum leak in the manifold from pcv or other will definitely cause all sorts of probs as the MAF isn't measuring the true metered air going into the engine, mixtures will be very wrong and exhaust lambda won't match what engine is expecting= CEL.

[Ryan_R]

It's just the normal cool-down hissing sound that we're all used to - it's only changed so that it's intermittent now

[manny76]

Manny, this thread is about engine not running= no vacuum. Only place with vacuum after engine stops is in the brake booster. You can confirm the booster check valve isn't leaking by pressing your foot on the brake before starting and listening for a low sound of air. Pump the pedal a couple of times and you will feel it becomes solid rather than softish(from the stored vacuum boost running out).

But yes, a vacuum leak in the manifold from pcv or other will definitely cause all sorts of probs as the MAF isn't measuring the true metered air going into the engine, mixtures will be very wrong and exhaust lambda won't match what engine is expecting= CEL.

I disagree to a certain point. PCV was leaking down with the engine off. Try it, pull off the vacuum line with engine off. Yes vacuum leaks call all sorts of dramas very true. My check light came on because ecu can only compensate/work in a certain range to control idle speed. Once out of that range it logs a fault and light appears . I disconnected the battery to test and it would idle perfect for a day or so, then play up.

Initially I thought it just was a/c system hissing.

Sorry if this is a hijack guys, just was wondering putting a different angle on possibilities.

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