Leempolo3

Hey everyone,

New owner of a 2006 E55 here. My first post was "car dead!" where a lot of good folks here have been helping me get the car up and running. Instead of adding this to that post I figured it would be more appropriate to start a new thread. Below I have included my other post as well as a youtube video of this annoying hissing sound. I can't pinpoint where its coming from but it's definitely the loudest right in between the oil cap and oil filter cap. It's also at its loudest when the car starts from a cold start but dwindles down once the car is driven and is warmed up. I sprayed brake cleaner all around the area to see if the idle changes and it didn't. Any thoughts? Thanks guys.

https://mbworld.org/forums/w211-amg/...-car-dead.html

HeissRod

Does the car have aftermarket exhaust work?

Leempolo3

No, all stock... I did have both valve cover gaskets and spark plugs changed.

HeissRod

Either you have exhaust work you don't know about or you have exhaust issues, cause that is not how a stock E55 sounds.

Elhonaz

If its on cold starts maybe its the secondary airpump, or the hose coming from it thats loose or has a crack. I forgot mine loose just the other day started my car it was veryloud. Also onetime had the hose that connects to a metal pipe that goes on back side of the SC loose, that connection is next to the fuelrail connection. BTW what is that plastic pipe that is connected to rubber hose by a clamp? This seems like somekind of vacum line but mine does not have that, atleast on the same location. Can be seen from 0-14sec mark and the hissing atually gets louder at 6sec when you move the camera closer to it!

Leempolo3

HeissRod, the car was owned by my dad originally and I assure you he did not do anything with the exhaust lol. I did see the exhaust removed (it looked like from the cats to about mid way) when the shop was working on the car and it was stock. But just out of curiosity, why do think that sound has something to do with exhaust? Wouldn't that come from under or the rear of the car?

Leempolo3

Elhonaz, I have no idea what that pipe is... that is the drivers side of the engine right under the air intake (which is removed in the video)

HeissRod

Your video makes the car sound like a 3rd Gen Camaro halfway submerged in water with missing mufflers. E55s do not sound that guttural or loud stock.

I do not know if this pertains to the hissing issue. However, if the shop has the exhaust off, that could be an exhaust leak.

Does the hissing sound get closer if you put the camera close to the intake hose?

Leempolo3

The video does make the car sound worse than what it actually sounds like. That was recorded with my phone. Also, that was right after I fired up the car from a cold start, she settled down a bit after that.

"Does the hissing sound get closer if you put the camera close to the intake hose?" I'm not sure what you mean, this was recorded with the intake hose removed. It sounds the loudest and closest when I put my ear right in between the oil cap and oil filter cap.

HeissRod

Does the hissing sound get closer if you put the camera close to the intake pipe going into the air filter box? I know you removed the hose. Do you still hear the noise with the hose in place?

Leempolo3

No, its coming from somewhere by the oil cap and the valve cover. That is the area where it is the loudest. See pic...

HeissRod

Does the hiss change with throttle input?

Leempolo3

Great point, just tried it out... Dad did it slowly while I put my ear to it and it got louder with more throttle.

HeissRod

Make a spray bottle of soapy water, then spray it in various places while watching for bubbles to form.

Leempolo3

Thanks Heissrod. Does it matter on a warm or cold engine?

HeissRod

Not much, but the soapy water would evaporate quicker on a hot motor. However, if it's an exhaust leak around the manifold, then it will be more prevalent at warmer temps. I'd try it at both temps.

Leempolo3

So I sprayed the crap out of that area with really soapy water and nothing... I had someone give it throttle and again no bubbles anywhere. I thought for sure there would be some since the hissing is so loud. Any ideas of what my next step should be?

Elhonaz

well the hissing is clearly something leaking, so you just have to figure it out by feeling and trying to listen where it comes from.

Hulk

Look at the legal vacuum line that comes from behind the supercharger, it goes to the side all the way to the front, there might be a hole there. I had the same thing and there was a small hole on the metal line near the front side of the car

O-55

From your picture, you seem to have a leak from your power steering high pressure hose. The sound could be coming from your power steering pump due to low power steering fluid.

Leempolo3

Thanks Hulk, I'm going to check that out tomorrow.

O-55, I've heard that low PS fluid usually makes a "groaning" sound. True? Either way, I'll take a look at the PS hose like you suggested. Thanks!!

Sir-Boost-a-Lot

iTrader: (1)

Take the oil cap off and put your hand over the top of it. Do you feel pressure?

Leempolo3

Sir-boost-a-lot, thanks for the suggestion. This is probably a dumb question, but do I do this with the engine running?

HeissRod

Yes

Sir-Boost-a-Lot

iTrader: (1)

If you feel pressure from the oil fill port with the engine running you've got one of two problems.
One is a leak in the tubing that connects the vaccum side of the intake tube to he valve covers. This will result in the intake not drawing a vaccum on the crankcase and the minimal amount of blowby has nowhere else to go. If this is the case and that fill cap wasn't vented, it'd probably start blowing oil out of the front and rear main seals.
The other possibility is that theres a problem in the bottom end of the engine such as failing piston rings. There's a ton of things that could cause this but it's fairly unlikely and very expensive so hopefully that's not the case here.