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Hood cowl engine compartment water seal questions

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by 2009Prius, May 14, 2010.

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  1. 2009Prius

    2009Prius A Wimpy DIYer

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    I have some questions around the water seal for the engine compartment.

    The first is the cowl cover seam, where I have read many times that it may leak and cause corrosion in the spark plug coils. But last time when I removed the cowl covers I found that there is a piece of foam sandwiched between a pair of pretty tall walls at the ends of the two plastic cowl cover pieces. It wasn't obvious how to apply additional sealant along the seam. Here are some pictures:

    Looking from above:
    [​IMG]

    Close up:
    [​IMG]

    Looking from below (hard to hold the camera):
    [​IMG]

    Close up:
    [​IMG]

    Is this piece of foam enough to stop the water? Is it an improvement over earlier years, or, does earlier year cars have this foam in between the two cowl pieces? Look at the last picture. If water would come out of the seam, wouldn't it be even easier to come out of the two slots where the plastic cowl cover pieces latch onto the metal cowl tray? :confused:

    At any rate do I need to apply silicone along the seam somehow? The funny geometry would make it ugly though.

    The second question is about the seal between the hood and the cowl cover. There is a rubber weather strip on the cowl cover and there is a matching foam strip on the underside of the hood, but the foam is shorter than the rubber. In this picture we can see clearly that it seems there is a piece of foam missing on the right hand side:

    [​IMG]

    Close up pictures show water get on the rubber (and maybe over into the engine compartment?) where there is no foam:
    [​IMG]

    Same on the other side:
    [​IMG]

    Why is the foam shorter? Cost saving? Fuse box doesn't mind water splash on it? Is it OK to add some foam myself? I want to make sure I won't block some intended gaps. Thanks!
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The foam between the two plastic cowl pieces is intended to seal the gap between the two pieces. That gap is typically where water may seep onto the valve cover. The foam is present on all 2G.

    In your case, with a relatively new Prius, I would not worry about trying to add more sealant over the foam unless you know you have a problem with water dripping onto the valve cover.

    Regarding the foam gap on the driver's side of the hood, I wouldn't worry about it as I do not think the amount of water that might enter is enough to cause trouble.
    1 person likes this.
  3. hobbit

    hobbit Senior Member

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    I dug into my own cowl this afternoon, and this is what I found:
    http://techno-fandom.org/~hobbit/cars/priwater/89wetcowl.jpg
    Totally plugged up, not draining until I poked through the ook
    with a screwdriver. Once the water ran out I continued disassembly
    and wiped all the goo out of there with a wet rag. It was a
    swamp. Sort of like wiping your ass when you're having one of
    THOSE days. With a sprinkling of stray acorns from my li'l
    rodent friends who like to party in the Prius. Nonetheless,
    this can easily be a yearly ceremony a little after "green car"
    season arrives, i.e. there's a thick coating of pollen all over
    everything. It accumulates and builds its own blockage in the
    drain holes.
    .
    I've noticed that the drain holes in the outer firewall piece are
    quite a bit larger in later model-year cars. Someone learned.
    .
    With all that out of the way, it was time to pull the ignitors
    and inspect the plug wells again, and it was good thing I did.
    #1 definitely had evidence of rust down at the bottom, and #2
    less so; the others were clean. Never seen that before, but then
    again it's possible that my own spring engine-cleaning ritual put
    it there rather than any cowl leakage. A bit of careful plug
    removal and cleaning later, all spanky on all four and back
    together with a fresh dose of anti-seize on the threads. This
    was after a little shy of 40,000 miles since the plug change,
    and I hadn't looked at them since.
    .
    I don't think the rubber seals around the ignitor modules are
    quite what they could be in terms of sealing, especially if any
    water lands in the valve cover and then *sits* there. So part
    of the engine-washing deal will have to be covering the top
    with plastic or something first and then go at it. Looks like
    taking a run on the road after washing doesn't vaporize all
    the water out of there.
    .
    _H*
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes. Note the the one bolt holding each igniter is positioned on the back end of the valve cover, at a low point. The bolt doesn't provide much help for the seal.

    A possible DIY mod for owners who are having trouble with water entering the spark plug wells might be to put a thin ring of black urethane sealant on the bottom of each seal where it contacts the valve cover.
  5. 2009Prius

    2009Prius A Wimpy DIYer

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    I added some foam strip to the hood and within a day it conformed to the shape of the rubber strip and windshield wash tube very well. :)

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
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