Hylomar on head gasket, or not ?
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  1. #1
    1000+ Posts Beano's Avatar
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    Default Hylomar on head gasket, or not ?

    In recent months my 505 has been losing a little water and I can't see any leaks. No water in the oil either.
    Now it's leaking slightly more.
    I assume the head gasket is letting it through, so I'm replacing the gasket. The head was done a few years ago, but not THAT long. To prevent this occurring again I'm thinking of using Hylomar on the head gasket, though I've only done this twice before.
    You guys got anything negative to say about this ?
    The only potential problem I can see is that when I spray it on, it also goes on the thin metal rings which seal each liner.....right where all the compression is. Whereas I only want it to be where there may not be enough sealant-stuff already on the gasket.
    It's a Sasic gasket with only a thin blue line of sealant running around it .....lots of circles around those areas which need to be sealed. The rest of the gasket has no glazing which might indicate a sealant....it is just plain grey gasket.
    I guess the makers of Hylomar have formulated it to seal over the "fire ring" but I still wonder......
    Perhaps just a THIN layer would be best ?

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  2. #2
    1000+ Posts robmac's Avatar
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    I have used hylomar on block /head face on every engine I've built.

    I've never had a leak.

    I hang up the gasket and spray an even layer all over both sides, wait until it goes tacky (solvent evaporates)

    The place on the block and immediately fit the head. Fit the studs/bolts but only finger tight.

    Wait 5 minutes the tension down.

    Hylomar has traditionally been used on decompression plates without any gaskets at all as the sole seal. So I can't see a problem with the liner ring seals.

    Even if the gasket is "monotorque", ie marked as "no need to re-tension", I have always done a second torque down after 600 miles.

  3. #3
    1000+ Posts jo proffi's Avatar
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    Ditto what rob said.

    Put as much on as you want, I cant see that you could actualy put too much on as it would be squished out anyway,but you'd just waste the product.

    Jo

  4. #4
    1000+ Posts driven's Avatar
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  5. #5
    1000+ Posts schlitzaugen's Avatar
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    My guess is that if you have a leak there might be some distortion in either head or block no matter how tiny. I have a similar problem with my 205GTI but in my case, the leak is obvious and coolant comes out of the engine on the front at the block-head interface. I suspect there is a micro distortion there, just enough to let coolant seep out when all is dilated at operating temperature. No amount of any wonder product will help if that is the case. For me it doesn't matter because the coolant doesn't go in the cylinder or the oil gallery, so all I have to do is top up the coolant every once in a blue moon. I have noticed this problem in another engine I pulled apart and in the same spot, so there may be a deeper underlying problem there, but I just consider it academic for the time being.
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  6. #6
    1000+ Posts Wildebeest's Avatar
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    Beano,
    Have a look at the block under the exhaust manifold. My 504 was seeping coolant from the block to gasket face. There was evidence of leakage down the block*. A coolant smell being a give-away.


    I had the head lightly machined, used the gasket sans any extra sealant. [The gasket, mono torque]. Had the usual blue plastic? seal around the important places. Used the spec.angle tightening method. Not necessary but I followed up with a retorque around 1000k.

    *Inspect it with a mirror.

  7. #7
    1000+ Posts Beano's Avatar
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    Thankyou for your opinions and information, gentlemen. I'll be using the Hylomar as per your recommendations (despite the warning in the link above), to avoid a repeat of the situation like my current one or Schlitzaugen's. The danger is that it is possible to continually dilute the corrosion inhibitor without realizing it, and cause the head to be eaten away a little.
    BTW, Schlitzaugen....if you're interested, when I was in Supercheap I noticed an American product that works in the presence of glycol.

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