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[JamesT]

Hi, I have an air leak from the plenum on my 1997 2.5 Omega.
I can definitely hear air being sucked in.
If I apply light (very light - one finger) pressure to the top of the plenum the hissing stops.
I replaced the O rings on the Intake manifold but it still hisses when engine running.
Should there be any other gasket that I should check for?

[chrisgixer]

Check icv is sitting snugly and not leaking?

Vac pipe nuts are tight?

Breather pipes are not split at the ends or leaking?

Breather box (Eco tech bit) seals not leaking? Any oil residue around them?

Is the fuel,pressure relay vac piped trapped between the plenum inlet manifold? Or pinched seal?

Inlet bagpipes jubilees all tight?


If that all fine I guess your looking at the seals under the inlet to plastic wedge? Red spectacle shaped ones are they?

[05omegav6]

Failed seal on the breather box

Most likely the one between the breather box and the plenum if pressing down on the breather box stops it

[YZ250]

Check icv is sitting snugly and not leaking?

Vac pipe nuts are tight?

Breather pipes are not split at the ends or leaking?

Breather box (Eco tech bit) seals not leaking? Any oil residue around them?

Is the fuel,pressure relay vac piped trapped between the plenum inlet manifold? Or pinched seal?

Inlet bagpipes jubilees all tight?


If that all fine I guess your looking at the seals under the inlet to plastic wedge? Red spectacle shaped ones are they?

As said, Top Hat rubber seal under eco bit possibly. 

[hotel21]

A carefull wee skoosh of carb cleaner at suspect areas will result in a change of engine revs and pinpoint the leak. 

[05omegav6]

Is a skoosh somewhere between a smidgen and a squirt? 

[hotel21]

 

Skoosh is a magical colloquial Scots word.

It's either a generic name for fizzy pop or the release of a small modicum of air or liquid under pressure.

One of those words that sounds like what it means - the 'skooosh' noise as you release the top of a beer can, pop bottle or squirt an airline!!!!   

[chrisgixer]

A cross between a squish and a whoosh. Makes perfect sense, even with a Scots accent.

[05omegav6]

 

[JamesT]

Thanks for your replies.
I have checked everything.
The top hat gasket under the eco bit is a bit distorted but is not leaking.
I have tightened the lower inlet manifold bolts about 1/4 turn.
Everything seems to be Tight, not leaking, not split.

The engine has never been taken apart before now so it should be something simple?

[JamesT]

I have put it all back together and checked everything.
Still a hissing of air.
Sprayed the top chamber with cleaner and the hissing noise lessened but only when I sprayed the very top of the chamber!
Sprayed the top air chamber with ignition sealer and the hissing stopped
Could I have a leak actually in the chamber itself?

[05omegav6]

Failed seal on the breather box

Most likely the one between the breather box and the plenum if pressing down on the breather box stops it

If spraying around that area affects the idle, then that is where the leak is

If the seal is either mishapen or cracked it won't seal properly, hence your leak...

[JamesT]

I replaced the little top hat seal under the ecotech bit as it was misshapen. I also changed the gasket between the EGR valve and the air chamber.
I have checked an rechecked all pipes and connections.
When the engine is idling is tends to hunt at times which causes the car to vibrate.
Acceleration after braking or rapid decelerating is also a bit rough.

Is there a diagnose code reader that will read the codes for the late 1996/early 1997 Omega 2.5?
I have one that reads my 2001 Frontera but it will not read the Omega.

[Andy B]

....

Is there a diagnose code reader that will read the codes for the late 1996/early 1997 Omega 2.5?
 .....

http://www.omegaowners.com/forum/index.php?topic=90581.0

but I doubt it'll show up anything further