Help with leak in exhaust recirculation. | FerrariChat
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Help with leak in exhaust recirculation.

Discussion in '308/328' started by RichardAguinsky, Apr 9, 2008.

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  1. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #1 RichardAguinsky, Apr 9, 2008
    Last edited by a moderator: Sep 7, 2017
    I need help on a 1984 Mondial. US version.

    There is a leak in my exhaust which was traced to a hose on the front bank. I assume these are standard exhaust hoses I can buy at Napa, is this the case? I'll replace all of them while at it. The tubes are so hard that at first I though they were metal.

    Notice the rust on the exhaust valve in the pictures below. Do I need to take it apart and clean it? Or is there a simple replacement that I can buy?

    Also, where is the open tube on the rear connected too? I can't figure out where it goes. Middle picture.

    Thanks in advance.
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  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Apr 9, 2008
    The rusted valve is an air injection check valve (your '84 US MondialQV does not have exhaust gas recirculation). It is supposed to only allow flow in one direction (from the rubber hose into the air injection manifold) -- yours has failed and is letting hot exhaust gas reach back to the rubber hose (which is why they failed/got hard/leak). It's a standard GM valve available at NAPA, etc. -- do a search on "air injection check valve" (or just take the old one to the autoparts store to match it).

    That tube end in your middle picture should not be open (nor connected to something else) -- if it was, it would let exhaust gas out.
     
  3. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #3 RichardAguinsky, Apr 9, 2008
    This is great information. I'll take the valve out and take it to NAPA or other parts store. It is very rusty. I'll replace it with the hoses.

    The tube from the middle picture is just open. Should I put a cap on it? Where does it normally go to?
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #4 Steve Magnusson, Apr 9, 2008
    Last edited by a moderator: Sep 7, 2017
    See the attached jpeg and please comment (just so I'm clear on which "tube" you are talking about).
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  5. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #5 RichardAguinsky, Apr 9, 2008
    The engine had two loud leaks. One in the front of the engine (towards the cabin) and one towards the rear (trunk).

    I thought the rear leak was from the tube. But you are correct, the tube has a plug on it. So the rear exhaust leak was not from there.

    At the end of the tube, as you said, there is another valve, which is fine. I followed the hoses and the rear leak was from a loose hose under the radiador expansion tank (what is that?) I tightened it up and now the rear is quiet.

    The valve in the front (first picture) is rusty, as you said, and loose. I'll take it off with my hand and get a replacement from NAPA. Is there anything "Ferrari special" about this valve or the hoses attached to it? Any valve will do? Would it be worthwhile to replace the other one as well?

    Thanks!!
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #6 Steve Magnusson, Apr 10, 2008
    Last edited by a moderator: Sep 7, 2017
    Can you identify in this jpeg of your Mondial QV air injection system from the OM where you "tightened it up and now the rear is quiet"? The check valves shouldn't allow exhaust gas to flow back up into the hoses so that would be a sign that your 1-4 bank check valve should also be replaced. They aren't Ferrari specific, nor expensive, so I'd replace both check valves.
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  7. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #7 RichardAguinsky, May 16, 2008
    I replace part number 34 from the diagram above. It worked for about 3 weeks. The same valve is leaking again. I went back to the parts store and they never saw those valves failing twice before.

    I'll replace it again and see how long this one lasts.

    What else can be wrong here?
     
  8. RichardAguinsky

    RichardAguinsky Formula Junior

    Nov 12, 2007
    478
    Palo Alto, Californi
    Full Name:
    Richard Aguinsky
    #8 RichardAguinsky, May 17, 2008
    Sorry, part number B from diagram above.
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #9 Steve Magnusson, May 17, 2008
    Your MondialQV powerplant architecture doesn't really have a way to make one bank run significantly different than the other. With the common fuel distributor, you'd have a better chance of winning Lotto than having something go wrong with only the 4 ports feeding the 5-8 cylinders. And the ignition system can have one bank fail completely, but, for example, to have the ignition on one bank operate in some retarded manner, has never been reported here for your powerplant type.

    Those check valves are connected by a metal conduction path to the exhaust manifold so they are going to run hot. And this whole system was sort of added later so the 1-4 check valve getting a little better air cooling at its location might be reasonable. If you want to, or need to, get deeper, you'd need to make some comparison temperature measurements with a pyrometer at similar locations on both banks (e.g., cyl head exhaust port, header flange, air injection manifold tube, check valve body, etc.).
     

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