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So much for the decat - the smoke returns!!

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  • So much for the decat - the smoke returns!!

    I got the leak in the exhaust fixed and the car does seem to have more torque low down now.

    So I tried to recreate the conditions that get the car smoking to see if the decat has solved the problem. Drove the car to get it hot and then parked it and let it run, raised the revs to about 2.5-3k a few times and after about 2 or 3 mins........... the fooking smoke came back!!!!!!:mad:

    This time there was nowhere near as much as with the CATs on but it was still happening. After a short initial heavy(ish) smoke it settled down to only producing it (well enough to really see) when you revved the car.

    This time the revs didn't hunt at all and if anything the smoke looked more like oil than the weird grey stuff when the CATs were on. Could a small amount of oil cause the CATs to smoke heavily?

    So where to next::confused:

    No noticeable oil use
    No noticeable water use
    No loss in power, boost or torque
    Compression test says everything OK
    Spark plugs not 'oiled' at all
    Only happens when hot and stationary
    Turbo bearings were checked the first time it smokes and declared to be OK

    I still need to check the PCV hoses so maybe the valve is knackered and letting small amounts of oil vapour in (as Paul N suggested) how do I remove the weird looking metal clips?

    If oil is getting into the combustion chambers how can I tell apart for the fact it comes out of the exhaust?

    This is now really p*ssing me off, all suggestions welcome before I get really fed up and ditch the piece of crap :mad:
    Ex 1994 Avant - now driving a Lotus 340r

  • #2
    OK, seeing I work from home I thought - b*llocks to it and went and spent an hour or so under the bonnet.

    I was looking for anywhere that oil could get into the exhaust system. Checked all the plugs and they are all a very healthy 'tan' colour on the insulator around the electrode and there is no sigh of oil at all. To me that sort of rules out the combustion chambers?

    The air box and MAF are totally clean but the large hose from the MAF seemed to have a very slight film of oily dirt in it (and I mean only a very small amount) further investigation revaled that the hose/pipe circled in the pictured below had oil in it. Not loads but definite engine oil.

    It seems to me that this is some form of breather or pressure pipe from the rocker/cam cover that feeds back into the very bottom of the MAF hose just before the turbo thingy effort (if that is what it is).

    How has oil got in here? Should it be in here? Is it a fauly cam cover gasket that is letting oil into somewhere it shouldn't be and it is then getting into the exhaust via the turbo?

    Now there seems to be slight smoking all the time. I ran the car after my investigation to check everything was put back OK and it was much cooler than before and I still got smoke when I opened the throttle

    Somebody help - Please
    Attached Files
    Last edited by Dr H; 8 July 2003, 16:55.
    Ex 1994 Avant - now driving a Lotus 340r

    Comment


    • #3
      Leigh,
      ive always been under the impression that a 'slightly' oily breather system isnt anything to worry about, but id be interested so hear other peoples views, ive been toying with the idea of re-routing the breather system to some sort of catch tank instead of going to the maf-turbo hose, surely any air/vapour that moves back into the intake system is going to be 'warm' which wont help.
      on the kruemmer site theres some pics of a breather mod in files section.
      mihnea, are you using a standard breather setup on your car?

      martin

      Comment


      • #4
        Martin

        My car is totally standard in the engine department. I've checked some more breathers and I now don't think that it is causing the problem.


        The car now smokes all the time basically it looks like it is buring oil. At tickover there is very very faint smoke but at 2-2.5k it really strats to pump out.

        I checked the shaft of the turbo for play and I seemed to be able to get it to move sightly if I pulled and pushed in cetain ways but then I'd do it again and nothing so I'm not sure on that one.

        So why does it now smoke all the time? Is it just coincidence that it has happened as I have removed the CATs or is it something to do with less back pressure now they have gone.

        :confused: :confused: :confused:

        Leigh
        Ex 1994 Avant - now driving a Lotus 340r

        Comment


        • #5
          Leigh,

          The most likely candidates are the valve stem oil seals, these become hard after years of abuse. If your car is an early example or it's covered a decent mileage, they may be the culprits.

          The recent overhaul of my 3B head found the valve stem oil seals to be rock hard, allowing oil to seep onto the rear of the valve heads. This wasn't causing too much visible smoke, however, I the motor was starting to use a little oil.

          Another possible problem could be the crankcase pressure regulator. That's the round black thingy on the radiator side of the block. If that's fubared you could well be sucking oil vapour into the inlet system.

          The pressure regulator is about 20 notes from VagParts, may be worth giving it a try.

          HTH
          Steve.
          91 Modded 3B
          14 A6 Avant Black Edition

          Comment


          • #6
            Cheers Steve

            Car is a 1994 ABY (Avant) with 54,590 genuine miles. So not sure on the stem seals really. You may have read earlier posts about smoking and CATs. Now I have the CATs off it smokes all the time and it seems much more like oil smoke than the wierd grey stuff it was producing when it got really hot with the CATs on.

            I'm wondering if the drop in back pressure (removal of CATs) is something to do with the smoke now :confused:

            The PCV valve has already been suggested (by Paul N) so I might give it a try for 20 notes.

            Something tells me that the turbo is fooked though

            Leigh
            Ex 1994 Avant - now driving a Lotus 340r

            Comment


            • #7
              Leigh,

              As you say...unlikely to be the valve stem oil seals with such a low mileage (I wish mine had only done 50 odd thou)

              Also, the turbos are good for very high mileage, so It's unlikely to be down to that. If it is the turbo, the leak must be on the exhaust side, if not your inlet hoses, intercooler and plugs etc. should have some oil on them.

              Back pressure on the exhaust, or lack of it, could help draw oil out through the turbo bearing housing, however, how much and when is beyond me. Perhaps one of the turbo gurus on the forum could tell you more on that subject.

              Hope you find the problem soon, and it isn't an expensive one

              Cheers
              Steve.
              91 Modded 3B
              14 A6 Avant Black Edition

              Comment


              • #8
                Steve

                As you say seems to be on the exhaust side as far as I can tell.
                Other possibilites are blocked crank case breathers etc. but (now) constant smoke after a decat points towards turbo to me.

                But what do I know, I await comments from the afore mentioned gurus........

                Leigh
                Ex 1994 Avant - now driving a Lotus 340r

                Comment


                • #9
                  I think now that you have removed the cats and it is smoking all the time proves it is you turbo. I spoke to AET Turbos - http://www.aet-turbos.co.uk/ - when my car was smoking - occasionally I would get huge puffs of smoke sitting in traffic - it got that bad it was nearly engulfing the car. The guy I spoke to there asked if I had changed the exhaust - I have a custom and no cats - he said that turbos are designed to have a certain back pressure from the exhaust at idling and when you remove this you get the high pressure oil on one side getting pumped through the turbo bearings causing smoke - Am I making sense?

                  I got them to refurbish the turbo and all is well again.

                  They also sell new RS2 turbos for £650.

                  HTH
                  S2,RS2,S4 WB,RS4,S4 B8,RS6 C5,RS6 C6,R8

                  Comment


                  • #10
                    Cheers Doug that's really useful.

                    They are only about 30 miles up the road from me, I knew there was somewhere near to me but couldn't think where it was.

                    Can I ask what they charged and how long it took. Was it a K24 or RS2? Do you know the cost of exchange units?

                    I guess the real question is why it has gone after 55K.

                    Finally have you ever changed a turbo yourself? Easy or difficult?

                    Questions questions.......

                    Cheers

                    Leigh
                    Ex 1994 Avant - now driving a Lotus 340r

                    Comment


                    • #11
                      Doug

                      I've read the other post thanks.

                      Leigh
                      Ex 1994 Avant - now driving a Lotus 340r

                      Comment


                      • #12
                        I have the same smoking problem from the turbo bearings, due to the low back pressure. Although it is a new turbo from AET!! Mmmm, im not that bothered about it cos soon as i drive it the smoke just goes, could well be your blower on its way out! They do go early if not allowed to cool down after a run or if switched off straight away when the turbo is still spinning.
                        Always let it idle for about 30 secs or more if you can.
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                        Tom C - www.rcmr.co.uk
                        Audi UR Quattro
                        Audi 100 C3 2.0 5 cyl 115ps
                        Audi S2 - 07k engine project aiming for 800ps
                        Audi B5 RS4 645ps 911nm

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