I'm looking into fitting a catch tank to my car, as I'm fed up of oil getting all over the TB and into the intercooler.

I had a good read through some threads on here, so I know what people have done before.

I was just wondering if anyone knew if I could remove the suction spray pump system, without ill effect? I have highlighted the hoses in question on the attached picture. I was thinking remove all of the breather hoses, and replace with some fresh decent stuff. A direct connection from crank case breather outlet, to the catch tank.

Obviously the tank would be plumbed between the blue marker and red circle. Or maybe vent to atmosphere, via a small filter. Haven't decided yet.

I just can't find any info on the suction spray pump! I'm assuming it's there just to atomise the vapours?

Cheers

So nobody knows what this breather pump thing does then? Or how it works?

I'm just curious more than anything else, so any ideas would be good.

It's odd that I can't find any information on it, maybe it's really obvious and I'm a retard!

I'll have a better search on the mk4 forum tonight and see if I can find out. The VW boys that mod their cars seem to strip off all the unecessary engine systems...

I think that one is a little out of our range on here.

Ukmk4's might help as you say.

It might work however there is one possible problem with not routing the crankcase air back into the intake. The engine ecu software is written for a certain % of that returned after the MAF. there is an adaptive vaule for it in measuring blocks. Im not sure how the car would react if this was removed. I'm not running any on my 1.8T but then im running aftermarket management, Its sound in pricipal.

Found some intersting stuff here: 17705 the Saga is over (well for me anyway!!!) - uk-mkivs

Where you guys getting these info drawings from?

Well, it's been almost a year and I still don't know what this suction spray pump does! Don't suppose anyone else does yet?

Hopefully I'll be getting a nice catch tank soon, so I've started thinking about this again. I guess if I don't know what it is (red pipework highlighted in the 1st post), then I should leave it alone....

Well obviously it sprays your suction dunnit

Try removing and see what happens, you'll soon find out if it's important.

And on that helpful note...

Helpful

The suction spray pump and PCV valve together do atomise the vapours.

The suction spray pump uses a venturi effect to increase the vacuum between it and the PCV valve, so I guess that is why it is called a pump. The spray is actually created by the PCV valve. The greater pressure differential across it produces a finer mist.

If you want to add a catch can, you need to remove this, as a fine mist will pass right through the catch can.

another name for it is suction jet pump. what it does is make sure there is vacuum available for the brakes under boost or on overrun. they were prone to leak boost on earlier ones as they used to come apart at the widest point. lots of info on UKmk4's and vwvortex. they are about £13 IIRC as I changed mine trying to eliminate issues

Finally! I know exactly what this thing does and when now:

Suction jet pump - Patent 6270321

(sign up to the website if you want to download the PDF file with pictures)

Under boost, it does nothing as all the one-way valves are closed (1 on the breather T-piece, 2 internal, 1 on the brake booster line from the plenum). But, if the body is cracked this would be a source of boost leak.

Under vacuum, it does 2 things. Boosts the vaccum supply to the brake servo using a venturi effect, while at the same time drawing crank case vapours into the inlet manifold. During this stage all the mentioned one-way valves are opened. Again, if the body is split/cracked this will be a possible source of vacuum leak.

Simple and effective little device that I'll be keeping now that I understand it. I'll just attach a new hose to the T-piece and run that up to a Y-piece (where it joins the rocker cover breather hose), and then onto the catch can. The catch can will then vent to the PCV on the turbo intake hose.

OK so I was half right! I knew it was to do with boosting the brake servo so not a good idea to remove - unless you want to use the brake as a workout

It's all lies!! The Skoda diagram in my first post turns out to be wrong! I was changing a vac hose last night and noticed something funny.

The suction pump has NOTHING to do with the breather system on the AUQ. As before the air discharge nipple goes directly into the inlet manifold, and the first air supply nipple goes to the brake servo vac line, however the second air supply nipple does NOT go down to the crank case breather T-piece, instead it goes to the turbo inlet hose, with a one-way valve in-line!

What the hell! There is no evidence of this system in any manuals I've seen so it must be AUQ or RS specific. On the plus side, this means we have a nice simple breather system, identical to the AGU engines (the top hose runs straight from the crank case T-piece to the inlet manifold).

The suction pump still serves it's primary function of boosting the vacuum for the brake servo, but instead of using oily air to boost the flow, it uses fresh filtered air taken from the turbo intake hose (much better!). Under boost it still does nothing, as the 2 internal valves close, and the in-line valve on the hose to the turbo intake closes, preventing a boost leak.

It may have taken me a while, but I got there in the end! I'm just happy that we have the simple breather system.

And breathe.....

mines an ARX (4x4) and mine does go down to the T piece. I know cos its a PITA to change the jet pump as the pipes are the hard shrink fit cr4p as well.