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[Nickbat]

I'm sure this has been asked before, but 'fraid I can't find the thread....

Is there some sort of replaceable seal between the black plastic breather thingy with Ecotec written on it and the top of the plenum? The car isn't as smooth as it used to be and there seems to be a bit of a hiss coming from it.

[theolodian]

Yeah, I had to replace mine after doing the breathers.

[Nickbat]

Is it a plenum-off job? That means I'll have to replace the O rings under the plenum...again.

[TheBoy]

Is it a plenum-off job? That means I'll have to replace the O rings under the plenum...again.

nope

[theolodian]

Takes less than 5 mins, don't even have to disconnect breather hoses.  Tricky bit is that the cover is in 2 parts and there is a hidden bolt.  Take the top 2 bolts off and pry off the COVER being careful not to pry on the BASE.  You will be able to see when you look carefully.

The gasket looks something like this   [|    (|)  It is a kind of wire-frame hat shape, instead of a simple o-ring, round with a square hoop or handle across the middle.

[TheBoy]

Takes less than 5 mins, don't even have to disconnect breather hoses.  Tricky bit is that the cover is in 2 parts and there is a hidden bolt.  Take the top 2 bolts off and pry off the COVER being careful not to pry on the BASE.  You will be able to see when you look carefully.

The gasket looks something like this   [|    (|)  It is a kind of wire-frame hat shape, instead of a simple o-ring, round with a square hoop or handle across the middle.

If it has the short plenum, you'll need to remove throttle housing (good opportunity to clean it)

If extended plenum, do as Theolodian says above...

[theolodian]

Ah, ooh, er.  Extended plenum only 98+ 3.0 right?

[TheBoy]

Ah, ooh, er.  Extended plenum only 98+ 3.0 right?

Yup, and 2.6/3.2...

[jonny2112]

Got me worried now! I haven't noticed any hissing and I didn't replace any seal between the black box and plenum! Could it be the ICV not properly seated which is allowing the escape of air? Or perhaps the black box needs tightened, which can be easily checked simply by removing the top cover.

As far as the difference between the two types of plenum - it is really obvious, but as said the throttle assembly needs to be removed before the breather box can be removed on the short plenum.

[theolodian]

Apparently very rare, but my gasket was torn while taking the breathers out to clean them.  Was the weekend so stuffed it back together best we could.  Ran like cr@p until could get new gasket on the Monday.  

Worth checking ICV and whatnot.

[Nickbat]

Thanks for all your input, guys. I've got a 95, so it'll be a throttle body off job.

Unfortunately, I think my problems may be worse than that. On the way home tonight, it sounded really rather rough on full throttle and it was accompanied by a sort of rattling which seemed to be coming from behind the instrument panel - so I'm thinking maybe exhaust manifold on the drivers side? Revving when not under load sounds OK, and it ticks over quite reasonably. If it is the exhaust manifold, then that's it...the car's off to the knackers yard!  

It could still be the plenum box, or even new plugs required - I admit it's been about 12 months since I last changed them. I know that's a crime, but I've been led to believe that NGKs are good for at least that (about 10k miles).

Looking after Nickbat junior tomorrow (I mean today, crikey look at the time!), so it'll be a day of jigsaw puzzles and Cbeebies!

 I'll try and take a closer look on Thursday.

[theolodian]

Full throttle isn't an intake leak, no vacuum.  Idle is where you see intake leaks the most.

Plugs last more than 10K!  Well, not a fan of NGK's personally but still.

[Nickbat]

Rattling seems to have disappeared for no apparent reason ( ), so it's back to looking at the plenum issue because the car's just not sounding right. I wouldn't call it a misfire, but it it isn't as smooth as it used to be and the overall engine note seems to be lower. Also, when cold it doesn't start on the first key turn as it always has in the past.

I'm pretty sure that I have a leak in the plenum area. As far as I can make out (looking briefly at the VX parts diagram at the dealers yesterday), the breather box on mine ('95) has an O ring seal between it and the plenum. Can anyone confirm this? Also, if anyone has a part number for the throttle body to plenum gasket, it would very useful.

[TheBoy]

Yes, as Theolodian confirmed a couple of posts above, there is a sealing ring between black plastic and plenum.  Don't know part number, but dealer will know...

[Nickbat]

Thanks for that. The reason I queried it was that Theolodian described a "wire frame hat shape", rather than a simple O ring and yet I could only see an O ring on the Vx diagram. I now assume that the gasket Theolodian was describing is feature of the post-98 extended plenum only.