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2002 Golf S 1.6/16v BCB
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Discussion Starter · #1 ·
Ok gents, just wondering if there's an alternative oil filler cap for a mk4 1.6/16v bcb engine ?...

Mine's got the stoopid filler neck setup with the breather/one way valve thingy and I'm wondering if there's an alternative cap with a one way breather built in...

Does that breather really need to be there, what exactly does it do, I know it lets air into the top of the motor but why does it need to do this as opposed to drawing air from somewhere else in the motor, what difference will it make if it's not fitted etc etc...

Any advice most appreciated as always... 馃憤
 

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from what you describe it sounds like a build in ventilation cap ( positive crankcase ventilation because it is one way) basically it get's rid off the blow-by from the valves opening and closing ( it is normal all ICE engines have that) and you need to keep that intact, or you will blow out the seals of the valve stems...

so just keep it as is.
 

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2002 Golf S 1.6/16v BCB
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Discussion Starter · #3 ·
So need to sort out how I'm going to reseal the ridiculous filler neck system then, that or find some alternative way of routing that pipe that doesn't involve leaving that neck in place... 馃憤
 

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2002 Golf S 1.6/16v BCB
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Discussion Starter · #4 ·
Draws/allows air in doesn't allow pressure out again... 馃憤
 

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had to look it up myself i've never worked on a BCB other than rip the engines out... but as soon as you said it let's air in i remembered seeing someone complain about his bcb on another forum... so read it here this forum... basically you'll need to replace the part an the part number is displayed on the topic... as how you describe it you have the same problem, a failed diaphragm.
 

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had to look it up myself i've never worked on a BCB other than rip the engines out... but as soon as you said it let's air in i remembered seeing someone complain about his bcb on another forum... so read it here this forum... basically you'll need to replace the part an the part number is displayed on the topic... as how you describe it you have the same problem, a failed diaphragm.
I think they're on about a different part. OP is talking about the pipe from the airbox to the oil filler neck, whereas that thread is referring to the oil separator unit on the back of engine, but that unit is something OP should be checking so this is still good info for him.

Draws/allows air in doesn't allow pressure out again... 馃憤
The pipe to the filler neck is only meant to allow air in, so that's working as intended. The oil separator on the back of the engine is only meant to be blowing air out the bottom via a 1mm hole, so if that is sucking air in then the diaphragm is broken. You can't see the hole from the top, but if you look down you'll see a circular part on the unit, and at the bottom edge of this is the hole to check. This unit is also renowned for causing an air leak due to its poor design. I have resealed mine with RTV, it made no difference to how mine ran, but it may help yours.
 

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2002 Golf S 1.6/16v BCB
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Discussion Starter · #7 ·
Cheers for the input gents, yes, initially I was on about the oil filler neck and for the life of me don't understand quite what VW was trying to achieve when they designed this part, nore what the designer was on when he came up with the idea but hey, t'is what it is although a simple spigot cast into the rocker cover onto which the tube for the breather/valve assembly was attached would have been perfectly serviceable...

The next rung on the ladder is the PCV valve and associated pipe work, been hearing/reading lots about replacing these valves with oil catch tanks as a way of eliminating any future issues, either of you chaps know anything about this ?...
 

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Cheers for the input gents, yes, initially I was on about the oil filler neck and for the life of me don't understand quite what VW was trying to achieve when they designed this part, nore what the designer was on when he came up with the idea but hey, t'is what it is although a simple spigot cast into the rocker cover onto which the tube for the breather/valve assembly was attached would have been perfectly serviceable...

The next rung on the ladder is the PCV valve and associated pipe work, been hearing/reading lots about replacing these valves with oil catch tanks as a way of eliminating any future issues, either of you chaps know anything about this ?...
The unit itself on the BCB is a bit odd so if you wanted a catch can you'd leave it all in place but add the can between the oil separator and the manifold.

You'd need 25mm ID tubing from the oil separator to the catch can, then either the same from the can to the manifold, or you can plug the manifold and vent the catch can to atmosphere - I'd go for a loop system and connect up to the manifold though.

It does introduce another area for a potential vacuum leak if you do go for a loop though, what with the extra pipework in place.

I ran with the oil separator venting and the manifold plugged for a while. Plugging the manifold and running like that was purely just to see if the oil separator was the cause of my intermittent lumpy idle, which it wasn't.
 
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