Wondering if anyone encountered this before.

I have a hissing sound coming from somewhere underneath the engine cover. It sounds like lightly pressurized air escaping from somewhere. You can hear the sound when the car is idle, the hood is open and your head is about a foot or two away from the engine. The pitch and the volume of the sound do not change over time - its a quiet, steady hiss. The sound is coming from the area circled in red in the attached image (not my car, but identical engine bay). I discovered the sound while cleaning out leaves from under the hood and I don't remember it being there before. The car drives absolutely fine (no loss of power, no other symptoms, etc). The sound is not related to climate control (I tried shutting it off completely and the sound is still there). My next service is in about 6 weeks so I'd rather wait (I don't want to waste time on dragging the car to the dealer yet). At the same time I don't want to get stuck on a side of the road somewhere.

 

It's normal, both of my Bentley's make the same sound from that area.

 

i got that sound too

 

that's the beginning of the plastic hoses splitting. they are wrapped with a heat shield that will easily slide down revealing the crack on the plastic seams. just up snap the cover pictured with the b on it. and put your hand over the two hoses (about the size of your pinky) mines started as just the hiss I even posted about it long ago was told that it was normal but it will eventually get worse and your pump will start to run more often especially when cold and when you hit the brakes.. maybe Bentley tech will chime in. this repair requires engine out so im going the splice mines and replace with rubber hose.

 

yep BentleyF is right,depending on year it is engine out,the split usually occurs on the right hand side and can be accessed by removing steering rack heat shield,we used to repair them and then found that on later cars we were getting splits on the pipework that is attached to transmission,the two hoses that join the intake are also prone to split and are easily replaced,not sure you can buy them separate but certainly can find after market bit of hose,best thing to do is carry out a smoke test from the vacuum tank and block off the rear pipes that go to exhaust flaps etc. this will give you a definitive answer to whether you have an air leak.

 

I knew that sound was not "normal". Damn...engine out on a 2.5 year old car? That's not cool. Good thing I still have the factory warranty. I really hope the dealer is not going to tell me "it's normal" when I bring it in for service next month.

Couple of questions for Bentleytech - does that cover just come off? No screws, fasteners or clips? I want to take a peek at those hoses to see how bad the split is, but don't want to break anything off. Also, what do those hoses carry, where do they come from and where to they go?

 

yeah just clips, Grab and firmly pull.

 

the cover with the flying B on just pulls up,the hoses are vacuum lines,there is a vacuum pump in the left hand wheel well on left hand drive cars ,from there the hoses go to engine,brake booster and to rear of car for exhaust flaps. if you pump your brake pedal continuously you will hear the pump run and if it does not shut off pretty quickly it usually means you have a leak,like i mentioned the best thing to do is carry out a smoke test.if you have factory warranty you have nothing to worry about and although engine out is a big job i have done loads and you would never know it has been out once they are finished.

 

I am just a tad concerned with the "you would never know it has been out" part. Maybe that's the case when you do it. The guys at my dealership had to remove the headliner to replace a satellite antenna last February and ever since then (4 service appointments later) I still have a rattle in the rear and a click in the left front pillar. If they can't manage to re-install the headliner properly, I can only imagine what they will do with an engine.

I'm also surprised that something like a plastic hose can go bad after only 2.5 years and only 15K miles of driving. Weird.

 

the problem is in the design,it is a hard plastic connecting to a metal "t" piece,it splits right there !! remove the cover and make sure the hissing isn't just the engine noise and feel around the hoses at the top to see if you can pin point,if they do a smoke test and it is leaking from the connection by the steering reach it can be repaired,although with car in warranty i would want a new one installed. with regards to the people you use i can't speak for them but you could always quiz them about how many times they have removed an engine and try and get a feel for the better one !!

 

i got this pic.

 

Here is what the dealership had to say:

Question for Bentleytech - do you think they are not doing enough troubleshooting?

 

if they have smoke tested it and there is no leak then there is not much more they can do,these engines are noisy and maybe you just did not notice the noise before. at that top end of manifold it does sound a lot.

 

Agree with BentelyTech. And yes, these youngish cars have a design flaw in the hose that runs behind the engine and the GTC here is doomed for an engine out eventually to fix the leaking hose. Hopefully the factory will find a way to help with the associated expenses with this known design flaw. Was quoted $3.5k to engine out from a factory dealer.

 

I have just found out that my car has the same problem and the split pipe is just above the bell-housing. Confirmed by a smoke test. Engine out job unfortunately.
This came to light whilst my wiring loom and cam sensors were fixed.
My car has covered around 66K.
Whilst the engine is out it's having a new exhaust gas sensor and a new pulley belt as the current one has got cracks in it.

Happy days.