After fitting a new breather system a couple of weeks ago, I developed a bad vacuum leak yesterday while on my way back from holiday. First came the 17705 code with boost limited to 5psi. After a key off and on again it was back to almost 10psi, but still not feeling right and not as pokey as normal. Then whenever the car idled the revs became irratic, sometimes reaching 1500rpm by itself! This then caused the car to go into limp mode again. It was pretty easy to guess I had a vacuum leak, but I got the following codes off it:

17544 - System too lean (tallies up with a vacuum leak on idle)

16891 - RPM higher than expected (I could see that!)

17705 - Pressure drop (most common and useless error code ever, as it could be anything, luckily I kinda knew what it was anyway)

Anyway, I spotted a split in the 90degree hose coming off the end of the suction pump, so I decided to bin the whole system, and tidy things up a bit. Here's what I removed:

Unlike other 1.8T's the vRS's AUQ has a suction pump system separate from the breather system. The cable throttle 1.8T's also dont have this system. Nobody I've spoken to seems to be able to give me a definate answer on what this system is for, but as far as I can figure out it's a safety measure for cars with a DBW throttle. Providing a vacuum to the servo even if the electric throttle goes apesh!t. I'm not certain though, that's just an educated guess based on patent I found on the pump. Anyway that's not something that worries me as I know how to handle a stuck open throttle, and I know for a fact that the throttles are fail safe (fail closed).

An M10 bolt and jubilee clip sealed off the inlet hole on the turbo intake hose. I replaced the Y-piece on the main servo line with a short section of 9.5mm silicone hose, providing a dedicated vacuum supply to the servo. I then used some 8mm silicone vacuum hose to connect the inlet manifold port for the suction pump, to the port for the breather system vacuum line, which essentially plugged both ports. As part of this I could remove one of the hardlines and a bracket.

Removing the vacuum line from the breather system was something that Westallc was asking about last week, so I thought I'd just give it a go! Tidies things up a bit more too. I'll get some snaps of the work tomorrow, as it's too bloody cold and dark to venture back out now! My hands are only just thawing out!

Been for a 30min blast and all is well again. Feels nice and punchy like normal, and the brakes actually feel better. So far so good........

Got to love this way we have of resolving problems with our cars - don't replace it, just pull it all out!

Nice job.

well done that man get some piccy up

well done that man get some piccy up

Here you are buddy:

I really need to give my rocker cover a scrub!

Here are the plugged vac ports on the manifold:

Been for another longer harder drive tonight over the peak district to test it out. Everything is good now, and throttle response seems much crisper than ever before. The DV also seems to be more responsive.

No error codes and no side effects so I'm happy!

What next...........

Got to love this way we have of resolving problems with our cars - don't replace it, just pull it all out!

Nice job.

Haha we're just "refining" things!

I think I need to ditch the SAI system like you next.

I was just modifying diagrams - mine's gone from this:

To this:

Ooops, just realised I forgot the catch can in that diagram. Doh!

Yeah that diagram from Skoda also gets the suction spray and breather system wrong. Took me a while to figure out what was going on when I first got those pdf's! It's correct for some other 1.8T's, but not the AUQ.

Our engines have an extra vacuum port on the inlet manifold (bringing the total to 5), and separate the vacuum line for the breather system from the vacuum feed for the suction pump (also including a hose from the turbo intake hose to the suction pump which isn't shown). It makes for a more reliable system, as it keeps the oil out of the plastic suction pump. But it means you have a right old birds nest of vacuum hoses under the manifold! Well, I don't anymore....

Definately have a stronger vacuum now, and better throttle response. Surprised how different it is actually.

Yeah that diagram from Skoda also gets the suction spray and breather system wrong. Took me a while to figure out what was going on when I first got those pdf's! It's correct for some other 1.8T's, but not the AUQ.

Our engines have an extra vacuum port on the inlet manifold (bringing the total to 5), and separate the vacuum line for the breather system from the vacuum feed for the suction pump (also including a hose from the turbo intake hose to the suction pump which isn't shown). It makes for a more reliable system, as it keeps the oil out of the plastic suction pump. But it means you have a right old birds nest of vacuum hoses under the manifold! Well, I don't anymore....

Definately have a stronger vacuum now, and better throttle response. Surprised how different it is actually.

That was my next job - trace the actual pipes in the car then correct the diagram

Then work out from there which pipes I want.

I was wondering about that extra port that you can see on your picture And I remember Steeviw Wonder saying the diagram wasn't right.

Okay I think this one is correct as mine is at the moment - N249 and SAI removed, suction pump as standard.

So how much VAC were you pulling pre and post mod?

Nice work rob, that's how the suction pump thing is/was on mine, so it's spot on now.

Spent another day fiddling under the bonnet today so I've put some updated pics in my service weekend thread.

Looks like the SAI pump has stopped working, so it's next on the hit list!

So how much VAC were you pulling pre and post mod?

Pulling about 26 inches of mercury now, but like a retard I forgot to check what it was before! Well it was leaking really badly before so the vacuum was proper low, so I guess it wouldn't have been a fair comparison anyway.

It's all starting to make more sense to me now I've drawn some pictures

How it was originally:

Pulling about 26 inches of mercury now, but like a retard I forgot to check what it was before! Well it was leaking really badly before so the vacuum was proper low, so I guess it wouldn't have been a fair comparison anyway.

I guess from searching previously that is about as good as it gets at idle. Mine is back at 25 on idle and 30 on the over-run since changing some of the really small vac lines like the one to the FPR

im going to remove all these systems next week

re run brake vac lines etc etc so will do a full report

i will be removing all the pipe work as well to really clean the engine bay up

I guess from searching previously that is about as good as it gets at idle. Mine is back at 25 on idle and 30 on the over-run since changing some of the really small vac lines like the one to the FPR

Nice, yeah that sounds the same as mine. Around 30 on the over-run, but it's hard to look at the gauge closely while driving!

I noticed today that the big hose from the DV to the turbo outlet pipe is looking a bit tired too. Possibly porous because I could see some splits starting on it. Guess it's the intense heat that it sees above the turbo. Soaked it in silicone spray to try keep it going for a bit longer.

im going to remove all these systems next week

re run brake vac lines etc etc so will do a full report

i will be removing all the pipe work as well to really clean the engine bay up

Awesome

I look forward to your thread on that. Even the little bits I've done have made a fair old difference to the look.

im going to remove all these systems next week

re run brake vac lines etc etc so will do a full report

i will be removing all the pipe work as well to really clean the engine bay up

Yeah I need to remove the hard lines down the side of the engine block.

Might do the suction spray pump at the same time.