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Discussion Starter · #1 ·
i took my car in to the dealers before christmas and told them the when i pull away the car makes a rasping noise from underneath. i thought it was possibly the catalitic converter knackered from when my coil packs went and vw assistance driving it from Bristol to Bath with all coil packs gone.

they told me it was the breather pipe and it was on back order so they would call me when it was ready. that has been a month now, but what i want to know is whether or not the breather pipe might affect the performance of the car or damage something else whilst i am waiting for the replacement?
 

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AFAIK the breather pipe (or crankcase breather) just recirculates oil vapour out of the engine back into the air intake (after the air filter) where it is sucked back into engine.

I put an induction kit on my pug 306, and had nowhere for the breather to go, so just let the oil vapour go to atmosphere (!) shouldn't cause any damage, just keep an eye on oil level, as if they mean that its broken or cracked, some oil vapour may escape out of the pipe to atmosphere, so may lose a small amount of oil this way, but shouldnt blow out a large amount.

Dont take that for gospel, its just what i think!
 

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Like Benn says, it should be fine. I've just got a little filter on the end of mine, it doesn't feed back into the airbox

If it's broken then you might get a small amount of oil leaking to the surrounding engine parts, but it shouldn't cause a problem other then not being very clean

In fact, find out exactly what it is that's wrong with the pipe - if it's a crack or something, you might just be able to do a repair with silicone-type sealant?
 

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So this pipe recirculates oil vapour or possibly oil if something goes wrong back into the clean side of the airbox?

It sounds strange as its going right over the MAF.

I thought it sucked air out of the clean side of the airbox hence putting a filter on the end of the pipe when using a CAI.
 

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Gary, when i replaced my MAF, i noticed that it was covered in a film of oil, i may put a filter on the breather pipe to keep all of the air intake system clean.
 

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it recirculates oil vapour back into the system via the turbo.

I.e as the turbo sucks in clean air a small amount of oil vapour also gets sucked in problem is after a while it can also gunk up other parts like dump valve.

2 things to watch out for tho

1. oil vapour fumes entering the cabin

2. oil vapour ignition, but unless you are running silly boost levels and your turbo is glowing hot.shouldnt be a problem.
 

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I don't think so Gary... what I mean by a filter on the pipe (not the same as what you said about having a CAI, as I don't have an airbox) is this:

Posted Image


This definitely pushes air and oil vapour out.

You don't want to be sucking air away from the engine now, do you? The CAI filter presumably just cleans the air back up on the way in rather than removing it by pushing it back out, so it delivers purer air to the engine than with a panel filter alone (this last bit is purely speculative).

Make sense?
 

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On the plus side for turbo cars.

you get a cleaner boost system.Crisper sounding dv (lots of you guys with CAI's would have noticed this).oh and if you do so happen to throw a piston your turbo wont injest litres of oil and self destruct.
 

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It's made by Pipercross, I got it in a local shop

Not sure if they sell them separately, mine came with my cone filter. Can always ask though...
 

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Quote: posted by Cat1.4 on 14/01/2005 14:07:57

I don't think so Gary... what I mean by a filter on the pipe (not the same as what you said about having a CAI, as I don't have an airbox) is this:

Posted Image


This definitely pushes air and oil vapour out.

You don't want to be sucking air away from the engine now, do you? The CAI filter presumably just cleans the air back up on the way in rather than removing it by pushing it back out, so it delivers purer air to the engine than with a panel filter alone (this last bit is purely speculative).

Make sense?

Cat, I cant see your picture but what I mean is the very small filter on the end of the 20mm or so dia pipe which enters the airbox at the side of the MAF.

I asked this exact same question a couple of months ago on SCN - this is the reply posted by techie (Ross)

"The plastic ribbed pipe with the push on connection?

If so then thats the inlet for the secondary air injection. Theres a little pump down by the sump (usually hear is humming on cold start up) it pulls in air which is pumped into the exhaust to dilute emissions whilst the cat is warming up and running on fast idle."

www.seatcupra.net/forums/showthread.php?t=43518
 

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IIRC the crankcase breather takes air and oil vapour from you crankcase,and hurls them directly at the MAF,without the benefit of filtration.This,of course,leads to the eventual death of the MAF.[B)]
 

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Like i said, i've only known about this from my old 306 - which wasnt turbo, so dont know what goes on with that - ond the only thing similar to what (i think) a MAF does was that it had a Lambda probe, which iirc was an oxygen sensor for the injection management, and this was located after the air filter of the induction kit, but BEFORE the location where oil vapour was recirculated. So the oxygen sensor never got oil blown on it.

I also tried using one of the little filters that Cat shows in her pic, but due to the location of things, the pipe with this filter on the end had to point downwards. Thus, oil vapour (and possibly gunge) collected and condensed on the inside of the filter, making it WET with oil, and therefore not very good at flowing vapour. The result of this was that this breather was effectively blocked and the engine got pressurised, and oil was forced out of the dipstick hole!

Took me ages to realise why the engine was always getting covered in a layer of oil.
 

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I have just been speaking to Andy, the head mechanic at Awesome GTI and he has confirmed what Ross said about this pipe.

Its not a breather pipe which puts oil vapour back into the intake system, think about it - you would have a dead MAF every week!!

What it does is takes air FROM the clean side of the airbox via a secondary air pump and puts it into the exhaust system making it run leaner for emmissions reasons. This only happens when the engine is running on choke, after that it doesnt do anything.
 

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Discussion Starter · #18 ·
Quote: posted by GaryM on 15/01/2005 12:01:26

I have just been speaking to Andy, the head mechanic at Awesome GTI and he has confirmed what Ross said about this pipe.

Its not a breather pipe which puts oil vapour back into the intake system, think about it - you would have a dead MAF every week!!

What it does is takes air FROM the clean side of the airbox via a secondary air pump and puts it into the exhaust system making it run leaner for emmissions reasons. This only happens when the engine is running on choke, after that it doesnt do anything.

so would a split breather pipe cause any engine performance drop and a droning rasp from under the car when pulling away?
 

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No it wouldnt but a split pipe may cause air from the split to be sucked into the intake system when the secondary airpump has switched itself off which isnt good as thats on the clean side of the airbox.

Either way Id get it replaced.

[EDIT] I suppose it could cause a slight rasp thinking about it.

As the pump calls for air it may also suck air from the engine bay into the split of the pipe.
 

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AFAIK the breather pipe (or crankcase breather) just recirculates oil vapour out of the engine back into the air intake (after the air filter) where it is sucked back into engine.

I put an induction kit on my pug 306, and had nowhere for the breather to go, so just let the oil vapour go to atmosphere (!) shouldn't cause any damage, just keep an eye on oil level, as if they mean that its broken or cracked, some oil vapour may escape out of the pipe to atmosphere, so may lose a small amount of oil this way, but shouldnt blow out a large amount.

Dont take that for gospel, its just what i think!
hey mate, ive got a peugoet 306 1.4 and im putting an induction on it but not sure where to attach the breather hose, ive seen two models of air induction for my car, theres one for £20 which i dont think has the breather pipe on it and one ten pound more which has a small blue tube coming from the main pipe suposingly to insert back into the top of the engine, i dont want to change anything so that the car doesnt run anybetter after putting on the air filter. what do you think? what about a small breather filter? but i thought the air was suposed to go back into the engine? thanks
 
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