Loud hiss under acceleration no black smoke

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Iskapsts

Member
Joined
Jun 20, 2020
Messages
48
Location
Bedford uk
Car
2008 viano lwb 3.0cdi
Hi fellow Mercedes owners,I’m a really newbie here and also with Mercedes as owning my first viano for 2 weeks,and I really need some advice here.It’s 2008 lwb 3.0cdi
The hiss ir really loud and starts at around 1500 rmp
Whenever I accelerate hard or gently.
It hissing even when decelerate until gear disengages and rpm drops to idle,hissing is only during drive when I presume turbo kicks in.infact the hiss is so loud that it makes people turn heads,at around 2000-3000rpm I cannot even hear the engine as hiss sound overcomes it.
Despite no black smoke from exhaust during hiss which most likely points to split intercooler hoses(as had with other cars) I have removed checked both sides rubber intercooler hoses no splits.
Checked turbo seal,inlet pipes all seems to be well,intercooler it self looked clean no fresh oil or anything suspicious on neither sides,besides all that didn’t notice any power loss,I’m really out of options here.could it be blocked CAT or dpf if these comes with dpf.
Any advice would be much appreciated.
Regards igors
*** little update,there is some air rushing escaping can be hear while stationary holding around 2500rpm,but it’s just mild compare to driving hisss wusshh.
 

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Last edited:
After long research to pinpoint source of hiss it all points to exhaust manifold.
Hello, I have the same issue with mine to be honest - Vito 120 CDI - is it hazard to the engine? I tend to smell diesel in the cabin when I accelerate hard to?
 
sorted:
lose clamp on cat and also loose clamp on dpf inlet also 2 bolts were missing from some bracket see pic. please.
touched by cowboy mechanic 4k miles earlier.
 

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Hello, I have the same issue with mine to be honest - Vito 120 CDI - is it hazard to the engine? I tend to smell diesel in the cabin when I accelerate hard to?
i also have fresh diesel sell entering trough vents i guess in cabin especially while on motorway,
turned out to be leaking injector feed,
clickmechanic last night advised that there is special tool for this like a L shape to gain access from side of bolt or something,
however wouldn't removal of resonator and return line give me enough access with some common spanner?
 

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