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Thread: Head gasket - where's the leak?

  1. #1

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    Head gasket - where's the leak?

    I had symptoms of a head gasket leak (overflowing expansion tank, erratic temp gauge & white steam from tail pipes) so I flat-bedded home. When I pulled the header I poured out a quart of coolant. I pulled the engine and the left head showed coolant in both cylinders but I couldn't see any obvious break in the metal gasket.





    Next, I pulled the right head and found essentially the same - both cylinders had coolant and I couldn't see any obvious gasket break.





    I'm puzzled by coolant leaks into all four cylinders. Is there anything that could cause that? Since I was trying to nurse the car home after the first symptoms, maybe it was when the second gasket blew that the steam erupted and the engine quit. I'd appreciate any experienced eyes to tell me where the leaks are, and why both heads leaked. Thanks.
    Last edited by AZPete; 06-12-2018 at 03:56 PM.
    818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities.
    Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).

  2. #2
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    One thing that it could be is a cracked head. Sometime they are hard to see. Maybe Wayne P or other expert can help.

  3. #3
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    I would also take a good machinst's straight edge to the heads and block and use feeler gauges on any gaps. There is a spec for warpage, but more than a few thousands and it won't hold, iirc. Head gasket leaks can be hard to see.

    Frank is also right, need to make sure the heads aren't cracked. I would highly suggest a machine shop to test them if you are unsure if they are cracked or don't find an obvious problem elsewhere.

  4. #4
    Member tenncobra's Avatar
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    I second checking for warpage. I had my truck overheat and also had white smoke coming out of the exhaust. I pulled the heads and had coolant in multiple cylinders. When I checked the gasket, I could not find any evidence of damage to the gasket. I eventually checked the heads with a straight edge and found them to be warped from corner to corner.

  5. #5
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    Look at the bottom of all four cylinders the black area on the fire ring sealing surface is black,indicating combustion gasses were passing into the coolant ports. See attached image. What boost pressures were you running?
    2FE1D2D3-4814-4E3F-9006-30A21AD2EEA8.jpeg

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  7. #6

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    DMC, thanks! Now that you pointed out the black areas, it's obvious to me now. I've located a straight-edge and found that both heads are warped with low points at the bottom of the cylinders. I'm now looking for a good machine shop in the Phoenix area and searching for parts. Thanks! Only 13 pounds boost.

    From searching NASIOC and other sites, it looks like best timing belt and head gaskets are OE. You agree?
    818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities.
    Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).

  8. #7
    fasterer and furiouser longislandwrx's Avatar
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    I've used the gates kits for timing belts with great success,

    https://www.flatironstuning.com/p-39...ater-pump.aspx

    Get the master kit from subaru... all the good stuff.

    https://www.flatironstuning.com/p-19...all-years.aspx

    you need valve covers and half moons... i like getting it from flatirons cause they built a nice package

    pick up a Subaru t-stat and gasket, they are thick rubber. everything else is junk paper
    A well stocked beverage fridge is the key to any successful project.

  9. #8

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    While you're in there, you may want to install a set of these:

    https://www.flatironstuning.com/p-19...x-and-sti.aspx

    Factory head bolts on forced induction motors stretch over time and can cause symptoms like this.

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  11. #9

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    I've filled my cart at Flatironstuning with the master gasket kit, ARP studs, water pump, timing belt, idlers and tensioner . . . and maybe more.
    I'm hoping they have a discount for a CU-Boulder alum, who has climbed the Flatirons!
    Thanks guys.
    818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities.
    Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).

  12. #10
    Sgt.Gator's Avatar
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    I have a few thoughts on this. Post up pics of your block. They frequently crack where they are scalloped for the bolts. Here's an example:

    ..

    Also check your heads close around the spark plug hole. This won't cause the leak you have but it's an inspection to do while the heads are off. Some folks say these cracks can be left alone and no issues will come from them. IMHO they are cause to toss the heads:



    The spec on the heads:
    Warping limit: 0.035 mm (0.0014 in)
    Grinding limit: 0.1 mm (0.004 in)

    and the block is:
    Warping limit: 0.025 mm (0.00098 in)
    Grinding limit: 0.1 mm (0.004 in)


    I have used Gates timing kits in the past but no longer recommend them. They are using crappy Chinese junk water pumps and tensioners now. Either use OEM Subaru or the Aisin kit. The Aisin kit is made in Japan. I see that Flatirons has that all figured out. Just don't get the standard or the racing Gates kits. I lost an engine at Pacific Raceways either because the tensioner failed or the tech who installed it didn't use Loctitie on the bolt. Gates has recognized that problem and includes Loctite in the kits now. Be warned, the Subaru factory repair manual does not mention using Loctite on any of the timing bits bolts, but IMHO you should use it on all of them!
    "Good Judgement comes from Experience. Experience comes from Bad Judgement"
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  13. #11
    fasterer and furiouser longislandwrx's Avatar
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    gator, the link i gave on flatirons is the gates kits with the oem subaru parts. tensioner and wp, its a $60 upgrade over the std gates kit.

    sorry read the rest of the post. you saw already.

    yes get the subaru oem parts i think its still cheaper than the aisen kit.
    A well stocked beverage fridge is the key to any successful project.

  14. #12

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    Thanks, Sgt Gator, for the heads-up on head & block cracks. I've checked both carefully and found no cracks, plus the machine shop that is doing my heads they will check also. (whew.)
    818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities.
    Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).

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