My euro shop guys do 100+ a year, frequently one or both surfaces are imperfect. They always use hol or copper. Comebacks blow.
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I have not arrived at my current process without experience. I used to promote installing dry with meticulous prep, but I have had a few issues. At this point in time I have had several dry fiber gaskets seal without issue. I have had several dry MLS gaskets seal without issue. I have had a couple fiber gaskets leak with low miles from the high pressure area between 3+4 despite both the block and head being true, flat and totally clean and brakeclean dry. I have had one dry MLS gasket weep between 3+4 despite being true, clean and dry. I have used Hylomar so far on three and have had no issues with sealing. This is not a large cross section but not tiny either. My conclusion is that despite METICULOUS prep of both block and head surfaces and having them totally flat, clean and dry they will sometimes weep with low miles. So far, the addition of hylomar has stopped that issue for me. Dry has about a 20% premature failure rate for me, albeit a very minor failure mode of weeping on on the front of the block and making a mess. Despite the current small cross section of head gaskets on which I have used hylomar, so far it has a 100% success rate. If I have any issues with hylomar, I will analyze and reassess what process I use. I would reiterate that in disassembling VW engines, it is clear that they do use a sealer on the head gasket and it gives me the impression that it is hylomar or darn similar.
Thanks libby. It's difficult to get to know people on the forums, but over time you eventually do gain some insight. The primary reason I visit is information and yours is always top notch.
Very much appreciated Sir.
BTW, excellent sticky material
I do hylomar as well. It works for more than HG.
I do hylomar as well. It works for more than HG.
Thanks theman.
I did a bunch of reading on Hylomar's website and the product libby recommended is good to 215 PSI in shear
1.5 N/mm˛
I think the initial assumption (at least mine) is that the sealer aids in sealing the head which is there primarily to seal extreme compression. The head also seals in oil and water as well (duh!) - all the time, hot or cold. My guess is that the hylomar keeps the oil and water from
seeping during temperature variations. What it can't do is seal against high compression and while it should be obvious to most of us, the sealer is
not intended to repair a bad surface. As both you and libby (and many others here) have considerable experience with the nuance's of these engines. . .
It eliminates the pesky minor oil leak that is common between 3+4.
No engineering is perfect and these engines are all well used (some not so well
). Apparently there is a weakness that can cause leaks even if the surfaces are very good.
I just ordered a can (38 bucks including shipping) as "pesky leaks" are something I'd like to avoid.
BTW - thanks also to rumbling_caddy for the original post - excellent info obtained!
Since we're on the subject, the cheapest place I've found for Hylomar is Amazon.com