Phantom oil leak / rough idle, air leak from block? - Advice requested


Registered User
Hi all,

Made a couple of posts, but I’m after some advice to lean on the experience here.

Firstly I’m a new member, so a bit of intro / background.

Just bought a A3 1.8TFSI S Line, to replace my Merc that someone decided to write off to save their brake wear...

Bought it cheap with a few obvious problems, which i hoped to pick through and give it a new lease of life... The exterior is in pretty good nick for the ages, as is the interior... its on 99,000miles


So i have ticked through the following little jobs -

Rear discs and pads

Repair the drivers interior door handle, spot of drilling and tapping

Front washer jets replaced as partially blocked, done, upgraded to fan type

Rear washer jets replaced as blocked

New wipers, just to cheer myself up one day

New battery in the remote - now she unlocks as well as locks! - the first help this forum provided :)

New front undertray

Now then.. the main event however - engine oil leak.

When i first purchased, this was pretty obvious, but i went ahead knowing that i could happily deal with most leaks, I’m an auto engineer by trade and have rebuild engines and done my own repair work for the past 20 years...

Perhaps i bit off more than i thought, as the first few days of ownership it was smoking at traffic lights etc.. i was nervously watching the oil level until the weekend..

So first up, the engine bay was drenched, looked like it had been leaking a while and covered most areas, so i spent a day going about some obvious easy wins, and then cleaned everything down so i could then later identify any further leaks.

Sump off, very clean indeed, pick up spotless, so resealed and refitted, starting to think someone’s been in here already..

Cam cover, i could believe that it had a weep, so popped that off and the cam chain cover vac pump etc.

This is where i found a missing rocker/follower!! (I popped a rushed thread up about this before!)

It had been spat out and was found in the well between 3 and 4 plug..


So a few days waiting for the TPS to get a new follower and hydraulic equaliser in, and i popped that all back together, resealed cover, new seal for cam chain cover, new vacuum pump seal, fuel pump follower inspected and all ok, cam chain tensioner was a letter revision and in good condition, chain stretch not severe..

All going well..

I noted that it had a new PCV valve a few months before buying, so double checked all was still ok with that - all working as it should be, nice taste of oil in the mouth, job done. Oil filler off..


Ok, so might explain the weeps, lets check the PCV pipe work..

This is when it started to get smelly... i checked the oil separator to PCV hose, and found it bunged at the bottom end... nice.

Connected to the oil separator on the block.. a hose routed straight to atmosphere by the steering rack!!!

Ok, so ripped that all out.. checked all pipes very carefully for O ring damage or cracks and put it all back together... now I’m thinking, that’s the leak sorted!

Small vacuum in the filler cap, all looking good, except, now i have a rough idle... great

So started to do some fault finding, and the idle is rough, but improves if the sump oil separator hose is removed from the PCV and the PCV blanked, ok so air is getting into the crank case and then the intake unmetered..

Check idle and part throttle fuel adaptions and they are 5% and 15%, backs up the air leak.. reset them, and it struggles to even idle at all until it readjusts..

No fault codes other than an intake vane fault, probably just gummed up, its intermittent and i cant think of a relationship directly. Ill deal with that’s once i can keep oil in her!

So that’s pretty much where i am at. Run around for a day, and she isn’t smoking as much at stops, but there is still oil leaking..

If i rev the car, the smoke starts immediately, i was thinking this could be due to a leak only at high oil pressures, but I couldn’t rev it and look at the at the same time, and the air leak issue makes me think its a crankcase leak rather than a pressure side leak, but who knows right now..

the newly cleaned block and gear box shows the following -

Oil all over the driver side driveshaft - and this doesn’t help as this thrashes oil everywhere..
No leaks from cam cover.
No leaks from vacuum pump area
Oil drops on the back of the block, can pool around the underside of the head where it meets the block
Turbo feed and return lines all look pretty dry
Lower heater matrix pipe wet
CAT wet, this is where the smoke is obviously coming from
On the gearbox end of the block, just below the heater water take off pipe, there looks to be a repair or the block, around the core plug, but this looks dry
Oil over the block to gearbox area, but cant clearly see the route its coming down.

No clutch slip, although rear main seal is one thought.. :(




Red shows where the oil residue is, Blue is where the block repair (JB weld or similar is, again, this appears dry.)


So, anyone got any thoughts?

Ive never known a head gasket to leak oil with no other symptoms, anyone else?

Anything else obvious I’m missing?

Any known issues here?

Does anyone have a 1.8TFSI block to show me where the oil galleys run compared to the repair on the end of the block?

I’m currently torn between engine out, or stacking up on oil and fitting a catch can to regain my idle!
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Registered User
I think you have two issues here unrelated—- the oil leak which you seem best placed and qualified to fix and crank case pressuring. It is is well known that the 1.8 suffers from worn piston rings which manifested itself by high oil consumption which Audi fixed in the warranty period and continue to do so. There’s lots of discussion across the Audi forums if you want to read about.


Registered User
Hi Sooty,

Thanks for the reply.

You are quite right, I shouldn’t immediately link the two issues, and i should look for the root cause too.

I have been tinkering agaian all day today, replacing the seal on the sump oil separator, and investigating further.

What i have learnt today, is that the rear main crank seal is toast. I removed the sump breather from the PCV, blanked the PCV to see if it still ideals ok like this, and in this state, with no vacuum pulling the crank pressure out, i could see oil flying out of the gap between the engine and bellhousing at the back. It was flinging in a nice ‘I’m coming off something spinning’ way, so clearly the flywheel is spreading it about! This spray was going straight onto the cat. Nice.

At the end of the block, i removed the liquid metal that someone had bodged on, as it was all flaking off. Underneath i found a small coolant weep, another nice find.

Puts me in an awkward position now, that both issues together really want the engine out to do a nice job of at the same time, but then that’s a slippery sl;one where you find yourself doing the clutch, cam chain, rings, oil pump etc, soon its and engine rebuild.

Need to take a look at options. And yes, probably best to compression test it first to see if its all worth it. -ill re read the oil consumption threads and see if there is a precedent for a 12YO 99,000mile 1.8tfsi with patchy service history! - I’m not holding my breath...


Registered User
Just in case anyone is following this, I have decided to take it in to a specialist to do the RMS, as that’s the main issue I have RN

Probably going to cost me a clutch too. Unless they discover a recently new fitted one in there!

Sent from my iPhone using Tapatalk

Benjamin Kyle

Registered User
How'd you get on with this mate? I'm sure I've seen your car for sale on Facebook.. What was the cost to have the RMS replaced?

I'm facing a similar issue with my 2008 DSG A3 2.0 TSI EA888.1. Oil dripping from the small hole between the engine and trans, and throwing a P0171 Lean code. I'm going to stick a new PCV on it to try and slow down the progressive damage to the RMS. I'm thinking of tackling it myself on the driveway, I've heard it's possible.

If the new PCV solves the lean code I'll probably leave the RMS for a bit.

Very annoying as I've've just fitted a bunch of stage 2 mods and I want it mapped but I think that will make the issue worse.


Registered User
Hello mate.

I paid 1200£ at a local specialist, and that was for a new RMS clutch and flywheel.

well worth it IMO, and it was driving spot on Afterwards.

yep the car is up for sale just before the lockdown as I have moved abroad now for a bit.

Once the box was delivered off the leak was very apparent and the seal had disbonded from the bolted carrier plate. There was oil everywhere and it had caused clutch slipping and heat damage to the flywheel.