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[Webby the Bear]

Afternoon guys,

So, did as Mark suggested and disconnected the brake servo pipe, blocked it off and ran the engine. Vac leak hissing did NOT disappear. So vac leak narrowed down to sandwich plate gaskets, inlet to plenum o rings and top hat / breather bridge o rings.

So with it blocked off I got my ears right down to the breather bridge and sure enough even though I've replaced the top hat gasket it was really loud from that area.

Sprayed carb cleaner under the breather bridge but no ''sucking'' noises so I'm thinking it's a small leak and not allowing the carb cleaner in; but big enough to make the hissing during car running.

Pulled breather bridge off and as I forgot to take photos i'll try and describe what I found...

The ''hole'' in the plenum where the breather bridge fits in to is all ''jagged'' and the paint of the plenum peeling off  so I think I need to either get a cheap replacement plenum or repair mine. How on earth can I repair this to make the hole ever so slightly smaller to help seal this up? initial thoughts are peeling off old paint and spraying some high temp caliper paint or something.

thoughts?

[TheBoy]

Firstly, stop with that carb cleaner trick. If the leak is big enough for that to work, you should be able to locate by ear.  However, remember that carb cleaner completely buggers up any rubber seal.

IME, the tophat fits nicely (assuming nobody has coated it in carb cleaner ), so may just be a case of repairing plenum. 2.5 plenums should be plentiful from any breaker 

[Webby the Bear]

Thanks Jaime. So I am right in thinking that I could still have a vac leak without the carb cleaner working?

And yes I will stop it 

So replacement best 

[chrisgixer]

Have you compared the sound of yours against the sound of another similar 2.5 engine? There's an element of done sucking noise with the plenums anyway.

[Webby the Bear]

I haven't Chris, no. However it's odd that there's a distinct hissing from the breather bridge / top hat area.

[omega3000]

BigG mite have spare plenum , i had one of the actuators off it .. Dont know if it was 2.5 plenum though 

[biggriffin]

BigG mite have spare plenum , i had one of the actuators off it .. Dont know if it was 2.5 plenum though 

Weighed two in about 4weeks ago,along with heads,and condensers.

[Webby the Bear]

BigG mite have spare plenum , i had one of the actuators off it .. Dont know if it was 2.5 plenum though 

Weighed two in about 4weeks ago,along with heads,and condensers.

No worries mate... i'll see if RobG can help; if not i'll pop up a wanted ad 

Out of interest, is there no way of sealing it up i.e. a repair that folk can think of? 

[05omegav6]

A ring of black goo outside the hole... The rough edges are nowt to worry about...

[Webby the Bear]

A ring of black goo outside the hole... The rough edges are nowt to worry about...

Exactly what I was thinking Al, obviously ensuring none gets in to the pin holes on the breather bridge 

For best results let it dry for a while?

[05omegav6]

I would put it on the flat top surface of the plenum about 5mm from the hole...

Bare in mind that the breather bridge will sound like it's hissing when the engine is running as there is air moving through it

So don't be surprised if goo changes nowt...

[Webby the Bear]

I would put it on the flat top surface of the plenum about 5mm from the hole...

Bare in mind that the breather bridge will sound like it's hissing when the engine is running as there is air moving through it

So don't be surprised if goo changes nowt...

 

[biggriffin]

Serek mite have plenum

[Webby the Bear]

Thanks BG.

I'll try the black goo first and then see if I need to replace 

[amba]

Got a complete 2.5 plenum here,but not sure if they differ from PFL to FL as this one was from a 1998 so has the throttle cable mounts etc.

Not just round the corner though from you