No, not normal. Yes, you have a tiny leak.

 

Mine has a hissing sound once opened for about 10 seconds. Is this normal?

 

No.

 

You need a trunk lock actuator. It will eventually stop leaking once the leak gets worse. The pump will see that it is sending the air to it for too long and will stop sending it so the pump doesn't burn out. You will know it when the trunk stops sucking down. Pay attention because when it stops sucking down water can get in and ruin your audio components in the left behind the panels. I've seen it happen.

 

So have I and it is expensive.

 

The Encyclopedia has a link to a post on a repair for the trunk lock actuator that may help. While the actuator is the likely culprit, it could also be from a small crack in the vacuum tube going to it. It might pay to check first - but don't wait too long. The possibility of burning up the pump, as mentioned, is real.

 

So from reading a bit..It seems the "hockey puck" may be leaking and causing the hissing. Does this sound right in my case? My soft close works perfect and truck pops and closes no problem,just a 10 second his once opened. THX ahead

 

Does the 2002 have the little handle that pops out when opening the trunk, and sucks back in a few seconds after closing the trunk? If so, does yours still work?

 

You are thinking of the W140 S Class system.

 

It's a feature of the early models.

 

Ah OK.

 

It's also a feature on my 2003 (Update) W220 S500L. I do not have the soft close doors or trunk/boot lid. Pity, as it sounds like a nice feature. My chrome handle pops out when opening the boot either manually or remotely. After the boot lid is manually closed there is a hissing noise as the lid is pulled down tight and then the chrome handle retracts. I was led to believe the M-B design purpose for a hidden handle was to avoid the operator having to touch a wet handle in inclement conditions.

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The later ones (facelift 03 +) have it if they don't have the auto closer. When coding the PSE with the star diagnosis machine it refers to it as the "dirt free handle".

 

My 2003 S430 has the retracting handle...

 

I think benztetec8586 nailed it. Cars with automatic closure of the trunk wouldn't need it. Neither my '00 nor my '05 has autoclose for the trunk, and both have (had) the handle.

 

The hissing is often caused by a crack in the vacuum hose (it's yellow) that sits inside the black braided plastic harness which is easily visible on the inside of the trunk towards the rear window. You can see when the trunk opens and closes. For some reason I can't fathom MB used a very stiff pipe which cracks easily. Just use a rubber hose cover and seal it with tape. MB changes the entire harness which like all things benz costs a bomb and doesn't last long. A common mistake is that when you have some aftermarket installation of reversing camera or laser jammer, the installer runs their wires alongside this harness, and adheres their wires to this causing premature failure of this pipe.

 

I have a picture.

 

Thanks I will dig around and report back.

 

Ok So I am back.....I removed the liner and looked at all vacuum lines none were cracked or broken. The funny thing is...The hiss is now gone LOL