Hi all,

 

I'm having an issue with my 2004 Skoda Superb related to the charger system (I would assume). There's a "hissing" when driving and going up in rev.

 

A bit of background:

 

- a year ago I had an EGR issue. I took it off and it was completely clogged. Cleaned it almost as new and works fine.

 

- replaced the 90 degree flexible hose that exits the EGR valve towards the plastic piping (towards the intercooler)

 

- replaced the 90 degree flexible hose that exits the intercooler and goes into the metallic cross piping in front of the car (and further towards the turbo)

 

Checked the car all around for oil leaks and nothing to worry about. 

 

Trying to locate the hissing (air leak) and to me it sounds that is the front cross piping (the metallic one that goes across the front of the car and connects the intercooler to the turbo). I can't be sure of that.

 

I might be wrong but it does feel that it's loosing a bit of power when accelerating. Might be just me.

 

If revving while stationary, the hissing is not that bad. Still audible at high revs but not as bad as while driving.

 

Did anyone had a similar issue and can point me into the right direction?

 

My mechanic keeps telling me that's the EGR hissing but I'm 99% is not that as I cleaned it a year ago and looked and worked as new. Already spent some money on the car and not looking to spend another @£200 for a new EGR valve.

 

The hissing started after I went to the mechanic with a P0299 error and he revved it to really high rpm for a couple of times and deleted the error. The error never came back but the hissing started. I'm assuming something got dislodged or something. Still pulls but I feel it's a bit lazy (no much) or maybe it's just that me hearing the hissing and assuming I'm loosing power.

 

Thank you in advance.

 

P.S. Located in West London. If anyone around that could have a look would be nice.

P0299 is an underboost error - combined with a hissing noise symptom, you probably have a leak somewhere in the turbo pipework or connectors / intercooler

 

22 hours ago, bigjohn said:

P0299 is an underboost error - combined with a hissing noise symptom, you probably have a leak somewhere in the turbo pipework or connectors / intercooler

 

That's what I was thinking as well. But now, trying to check when the hissing appears, I think it's not something related to the turbo pipework.

 

I'm aware that I had that error, but that error never showed up again but the hissing is present.

 

Just replaced the flexible hose that connects the plastic bit with sensors and the top part of the intercooler as I noticed some big play as well. Nothing changed. Noticed that one of the parts where the clips lock got broken and the clips doesn't lock on one side (it's the part that goes in the plastic piping with sensors - picture attached)

 

I'm starting to believe it might be something related to the exhaust system as the power loss might not even be, just me thinking there's a power loss when is hissing. But what could be if it's something with the exhaust system?

 

I can't even concentrate with anything, keep thinking about the car. What could be the issue.

 

If you or anyone knows a "TDI expert/specialist" I could visit around East London just let me know.

Has the major rev up sent something downstream and partially blocked something eg intercooler or catalyst?

 

With the bonnet up and revving the engine can you hear the hissing - if so get someone to keep firing up the revs and try to isolate where the hissing is coming from. You usually feel the pressure when hitting the revs and squeezing turbo pipes - compare and contrast either side of the intercooler. 

 

Is the vacuum side of things re the pd ok? A leak here could create a hissing noise - probably not so loud though. When you turn the engine off does it shudder? - and does the anti shudder valve move as the engine is turned off (it should!) - usually visible just under the engine top plastic cover with the bonnet up looking over the OS wing. This can be a clue if something is not as it should be here. 

If the clips are not properly seated then it will leak at boost pressure, the pipes will push apart and the O rings will no longer seal.

Quick update:

 

I was checking the vacuum pipes in search for a leak and found nothing (was doing that in my tea break at work and didn't had too much time). When I left work I noticed there was no more hissing but that's because the car went into the limp mode and turbo was not working anymore. My strong guess it's something related to the vacuum piping so I need to check that next. I got no error on the dash but I think it's P0299 underboost as that's the error I had previously and which was deleted by the mechanic. Also, the mechanic might've changed something (with parameters I would guess) and that's why it's not showing the error but the car is for sure in limp mode (drives the same when i first had the error).

Start at the Servo/tandem pump end (vibrations and heat can damage the pipe here - important for your brakes as well!!) to check everything thoroughly - leaks are not always obvious. I had one on a mkI pd in one of the small plastic pipes that looked like it was made that way, mine was caused by the pipe rubbing / wearing through over time because of the diesel vibration. After the T off near the servo I followed the pipes and disconnected at each stage to listen / feel for vacuum. It's worth checking if the EGR valve is OK as these can gunk up somewhat.

 

The anti shudder valve is a good indicator whether things are not right re vacuum as it's at the end of the line. It should operate/move when you turn the engine off - If you stand next to the car with the bonnet up it should be visible and you can easily see its operation (or not) when you turn the engine off.

 

Note Servo on UK is clearly on the OS - after T off vacuum pipes go to the NS to the EGR , back over to the OS for vacuum reserve(lookes a bit like a baseball) , turbo actuator and anti shudder.

 

I'm working from memory here as I haven't had my mkI Superb for 5 years now - still going strong under new ownership though.

 

 

Edited 5 September, 20205 yr by bigjohn