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    Thread: Lots of carbon residue in exhaust vapor

    1. Member
      Join Date
      Apr 29th, 2003
      Location
      Bainbridge Island, WA
      Posts
      900
      Vehicles
      2017 GTI, 1997 Lotus Elise, 1991 Lancia Delta Integrale
      03-17-2020 05:13 PM #1
      I am looking after a friend's cars while he is out of the country for a couple years. One of them is a '99 Passat (1.8T AEB engine).

      One of the monthly things that I do is get the engine up to temp and drive it back and forth to put things under load and exercise the brakes and clutch. Since it is in particularly space that whole time, water vapor from the exhaust gets left on the floor at the tail pipe exit. Unlike the other cars, the Passat's exhaust is leaving a carbon residue on the floor after the water evaporates. I checked the plugs and they look good. The tailpipe itself doesn't have carbon build-up.

      Anyone here know what's up?

      alan

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    3. 03-18-2020 12:52 PM #2
      There might be a slight oil leak from the turbo when the car is started. The turbo 'floats' on pressurized motor oil for its bearings. It also spins at up to 10k rpm when operating. Any oil leaks through the seals will end up in the air intake and be run through the engine and out the exhaust. So.....it's possible that the carbon is some residue oil from the turbo. If you pull the air inlet pipe off the inter-cooler, there will almost certainly be some oil there. A little is normal but more than a TBSP or 2 is high.

    4. Member
      Join Date
      Apr 29th, 2003
      Location
      Bainbridge Island, WA
      Posts
      900
      Vehicles
      2017 GTI, 1997 Lotus Elise, 1991 Lancia Delta Integrale
      03-22-2020 11:57 PM #3
      Thanks. I will check that out when I am doing the vehicle maintenance next month.

      I have owned a couple B5/5.5 1.8T cars ('97 A4 and '04 Passat), but never had to do anything with the turbo or intercooler on them. Where does the oil pool? At the hose at the bottom of the intercooler? Is checking this a bumper-cover-off task?

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    6. 03-23-2020 04:25 PM #4
      Yep, you can just pull the hose off the hard pipe and check for oil there. I don't think it's hard to access but I'm working from memory.

    7. 03-26-2020 01:52 PM #5
      There may be a decent amount of oil sitting in the crossmember intercooler pipe. I drill a self-tapping hex washer head screw on low driver's side and then remove it to let it drain out. Reinstall when done and you then have a drain plug for future checks/draining.

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