Removal of intake plenum on 308QV or similar | FerrariChat

Removal of intake plenum on 308QV or similar

Discussion in 'Technical Q&A' started by rjdavatar, Apr 30, 2004.

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  1. rjdavatar

    rjdavatar Rookie

    Nov 17, 2003
    36
    Zurich, Switzerland
    I have severe corrosion of the metal union tube, that inserts from the aluminium coolant cross-manifold into the water hose running to the coolant header tank.

    To replace the union tube, it seems that I will have to remove the intake plenum,
    to remove the cross-manifold, and then extract and replace the union on the bench.

    Can anyone provide a detailed (or any...) procedure for removing the plenum?

    The main problem seems to be that the fuel injector pipes greatly limit access to
    the 8 nuts on the plenum studs. The inner ones are particularly tricky, because
    I cant get a (very good quality) 13mm ring spanner onto them, due to
    the limited clearance to the intake throat. A flat spanner doesnt do much better.
    The forward facing pair seem totally inaccessible due to the injector lines.

    Should the injector lines be removed? If so how?

    Is there some special spanner, or a modification of a spanner, that helps access?

    Once the studs are removed, is there a trick for ensuring that spacers do
    not fall down the intake throat?

    Can the thick plenum gasket be reused?

    thanks for any suggestions!
     
  2. 348 Turbo

    348 Turbo Formula 3

    Jul 17, 2002
    1,837
    It's been quite a while since I removed the plenum on my old 308.
    Yes, you need to remove a few fuel lines. No big deal, but remember, the crush washers will need to be replaced, they are one use only.
    Yes, you will need to be a contortionist.
    Yes, you can use the large thich gaskets again, no problem.
    BE CAREFULL, as you said not to drop the nuts into the intake. Also, be carefull not to drop the small nylon spacers surrounding the studs. Just go SLOWLY and it'll work out fime. Patience my friend..........................
     
  3. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    It is a pretty straight forward job for someone that has hands the size of a six yr old. Prepare for a lot of skinned knuckles too.

    A) remember to disconnect yout throttle cable before you try to remove the throttlebody.
    B) you may have to remove the oil filter housing too--the pipe wedges in tight beside it.
    C) *** if you have 2 friends to help**** remove the deck lid before you start--It is about 10x easier with the deck lid off of the car. BUT you need 6 hands to do this---also-take a sharpie and mark circles around the boltheads on the deck lid before removing so you can put them back in the same place and not spend 4 hours trying to readjust it.
     
  4. Eric308gtsiqv

    Eric308gtsiqv Formula 3

    Nov 26, 2001
    1,955
    Orange Park, Florida
    Full Name:
    Eric Eiland
    I removed the plenum off my 308 QV a couple of years ago to refinish it. IIRC, it was necessary to unscrew the throttle cable from the lever attached to the plenum housing, as well as disconnect any hoses / sensors attached to the passenger side of the plenum. I didn't remove any fuel lines / injectors, but keep in mind that those thin loopy fuel lines do tend to interfere a bit.

    The bolts are removed from the underside of the plenum / intakes. The rear set of bolts are fairly easy to remove due to the easy access. The forward bolts are a little more difficult. I spread a soft quilt across the engine bay and draped over the fenders so as to not scratch the paint work, then I gently climbed up and laid over the engine and sort of "hugged" the plenum. Then I PATIENTLY removed each forward bolt carefully trying not to drop them down into the abyss of the engine bay. Once unbolted, the plenum should lift right off (might require a slight tap with a rubber mallet). Be careful though, as there are gaskets for each of those intakes that could fall off. It might be a good idea at this stage to stick a shop rag into each intake port to keep unwanted items from falling into those ports.

    Before reinstalling the plenum, it might be a good idea to go ahead and order fresh intake gaskets, as well as the gaskets for the throttle housing / lever and gaskets for the items attached to the side of the plenum.

    Reinstallation is, of course, basically reverse of removal. Those forward bolts will again require patience and laying across the engine. Once they are started by hand, they should tighten right on down without a fuss. IIRC, I used a combination wrench primarily for those bolts, with sometimes very small bites / turns due to the interfering fuel lines -- but it can be done! You'll also need a socket / wrench with a possible assortment of extenders.

    BTW, while you have everything apart, it would be the perfect opportunity to clean the engine surfaces that are not normally accessible otherwise, and check all hoses normally hidden from view. I also clean out the inside of the plenum and throttle housing too. I made certain to pay close attention to the nut settings on the throttle cable lever before removal so that I could match them up as close as possible for proper pedal travel adjustment.

    It took about an hour or so to remove, and less than that to reinstall. The cleaning and repainting took the longest. :)
     
  5. rjdavatar

    rjdavatar Rookie

    Nov 17, 2003
    36
    Zurich, Switzerland
    thanks for all your suggestions.
    I'm awaiting gaskets for the coolant cross-manifold.
    Then I'll get started. I'lll report then.
     
  6. rjdavatar

    rjdavatar Rookie

    Nov 17, 2003
    36
    Zurich, Switzerland
    I released the rubber tubes attached to the plenum, intending to remove it.
    However, after removing the throttle housing, I was pleasantly suprised to
    see that it might be possible to remove the cross manifold without lifting
    the plenum.

    I released the hose clamp on the cross-manifold end of the waterpump - cross-manifold hose. Then I removed the 4 13mm nuts that attach the
    cross-manifold. After shaking the c-m a liitle, it came free, and I was able
    to deliver it though under the plenum, and out at the oil filter end (without
    removing the oil filter).

    The key to success was a fine 13mm 12 side socket, with a lever-arm hinged in the end of the socket. I'll try to post a picture of
    this useful little tool.

    The waterpipe union is badly corroded, and there seems little hope of removing it from the cross manifold, short of boring it out, and re-tapping the hole.
     
  7. tifosi

    tifosi F1 Veteran
    Lifetime Rossa

    Sep 5, 2001
    5,382
    texas
    Full Name:
    Tom D
    I think having those hoses under there is another part of the dealer retirement package :) what a pain in the arse to get at
     
  8. rjdavatar

    rjdavatar Rookie

    Nov 17, 2003
    36
    Zurich, Switzerland
    Stahlwille 'flexi 29'
    (of course, the advertising image shows a number of different size tools, superimposed..)
     
  9. rjdavatar

    rjdavatar Rookie

    Nov 17, 2003
    36
    Zurich, Switzerland
    The union wall is paper thin, and has two corrosion holes.
    I found that the bore was entirely clogged between the two holes, suggesting
    that there has been no, or little flow along that route for some while...

    I strongly recommend that those of you who have not examined this water
    hose for some while - do it soon. It is relatively easy to remove the hose clamp
    over this union and, check it. It may even be easy to replace it without
    removing the cross-manifold. It is crazy to have this tiny piece of iron sitting there in the aluminium, waiting to fall apart.

    ** Are there any such silly danger spots in the 308s that one should be aware
    of? And where a little preventative maintenance could go a long way?
     
  10. rjdavatar

    rjdavatar Rookie

    Nov 17, 2003
    36
    Zurich, Switzerland
    The corroded union was replaced with a stainless steel equivalent.

    Re-assembly of the cross manifold (with new gaskets and o-rings), with plenum in place, was straight-forward.
     
  11. Dinodog

    Dinodog Karting

    Sep 2, 2009
    78
    Birmingham,Alabama
    Full Name:
    Dean Matthews
    I just removed the plenum on my 81 euro GTBi and it took about an hour to get it off. In addition to the procedures laid out in this post I found it was easier to gain access to the nuts on the underside of the plenum by first removing the oil filter and cold start injector. I also disconnected the four injection lines on the back side of the motor. I did not remove the engine lid as it was not at all necessary. Once the plenum is removed there is adequate access to all the topside cooling hoses that, judging from the condition of the ones on my car, were obviously overlooked on previous services.
     

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