On Liquid Gaskets And Their Application

Discussion in 'Workshop Forum' started by Paul Valente, Jun 21, 2017.

  1. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    Paul, just to be clear, I assume you are referring to this chamfer (red arrows below)?

    I could be wrong but I believe these boxes were originally designed before RTV sealants really existed. I always thought the chamfer was to eliminate any burrs or casting flash so the case halves went together cleanly without interference. But that certainly does not preclude them as good candidates for liquid sealants now. I'm not disagreeing at all, just thinking out loud on the 'intended' reason for the chamfer.

    Steve, do you mean you spray the adhesive on the gasket before installing it? And do you coat both sides?

    To be clear, I am asking these questions (to both of you) for my own benefit. I've changed my habits for such procedures over the years as new products/techniques become available. But I never really know if I'm doing what is best. You know, teaching an old dog new tricks. So I appreciate the education, thanks for any feedback.
  2. Paul Valente

    Paul Valente Automotive Engineer

    Motor City USA
    Dr.Jeff likes this.
  3. Jeff,

    I use the Hi-Tac on both sides of the cam box gasket. It does help it seal. Makes installation way easier too.

    On the transmission case I spread it evenly across the mating surface but quite thin. No need for a lot. If you have one of my recent builds with RTV instead of a gasket there is a tiny bead along the case seam. You have to look pretty close to see it but its there.
    Dr.Jeff likes this.
  4. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    This discussion of gasket sealants always bring up memories from many years ago, dealing with all the old adhesives that were used in the past. The sealants were basically glues or shellacs and with age and heat they became impossible to remove. Sometimes you caused damage just separating the two halves of the component. Prepping a surface to install a new gasket was a real job. And just like with silicones, etc these days, guys always seemed to use way too much. :(
  5. When I see that someone has used gaskets or sealant improperly, or as is often the case, _really_ badly. That is a big red flag that whatever work they did, that was assembled with this mess, is probably just as bad. One of the tricks I learned about using the Ultra Black RTV is; after application, immediately assemble the case and run the bolts down snug, but don't torque. Let it sit for about 10-15 minutes and then torque. The sealant sets up just a little bit before torquing squishes it out and seems to create a better seal.
  6. dragonsgate

    dragonsgate True Classic

    I am not above using liquid gasket in a pinch but prefer actual gasket if that is what was originally used.
    A lot depends on if it is used properly.
    About three years ago shortly after I had some surgery the shift solenoid went out on transmission of my wife's Dodge.
    I was going to do the job but my wife was concerned that I wasn't up to the task so we paid a garage $400 to do it.
    The original gasket was rubber but the mechanic used the stuff from a tube on the pan.
    It was a sloppy job and with in a week it started leaking.
    I got a new rubber gasket cleaned the surfaces and installed it myself.
    It has been dry as a bone ever since.
    One problem I have noticed with gasket from a tube is residue.
    I have seen engines with bits of gasket material in the bottom of the oil pan.
    My dad was a shrewd horse trader in his day but in later years wasn't as sharp.
    He bought a pickup from a good old boy that gives shade tree mechanics a bad name.
    The trucks oil light quit working so I took a look.
    A lot of electrical work under the dash and I don't think the PO ever bought a roll of wire in his life as there were short pieces twisted together every where. I cleaned up the wiring and installed a mechanical oil gage and would get a few seconds of pressure then it would drop.
    Pulled the oil pan and found a bunch gasket material there.
    Most of it was bits of what looked like permatex.
    There was so much that the oil pump would pick it up and the screen would become blocked.
    Pulled main cap and rod cap to see what the bearings looked like.
    Ever seen a badly scratched 45 rpm record?
    I put the caps back on cleaned the pan and reinstalled with a new gasket.
    Figured there was no knocking so filled with 20/50 fired her up.
    That 318 ran for another three years that I know of before we got rid of the truck for other issues.
    I guess my message is if you use the liquid gasket follow instructions and be neat.
  7. Paul Valente

    Paul Valente Automotive Engineer

    Motor City USA
    Like Steve wisely points out, people misuse tools all the time. I wouldn't condemn the use of a torque wrench because someone snapped off a bolt with one because they didn't know how to use it. Folks with great tools can still do bad work if they don't understand what they are doing.
  8. As some of you know I used to own an Aamco transmission center. I have seen more than my share of bad transmission pan seal jobs.

    Depending on which Dodge your wife had its very likely that the pan was fitted at the factory using Black RTV, without a gasket, and is designed that way. The rubber gasket was likely aftermarket.

    Most people over apply RTV. They lay a thick bead perhaps assuming the bead will form a gasket much like a rubber gasket. That's not how it works. As Paul noted in the original post the seal isn't the mating surface but the edges where it forms after being squeezed out from between the mating surfaces. It also fills the imperfections in the mating surfaces but it doesn't form a "gasket" in the same mechanical sense that a paper or rubber gasket does.

    When disassembling an engine or transmission that was sealed with a thick bead of RTV you can easily see the results. That thick bead ends up along the edge of the mating surface, either inside or outside the engine/transmission. It also fills the bolt hole passages and dowel pin bosses/bores. At its best its a mess to deal with on the next service.
  9. dragonsgate

    dragonsgate True Classic

    02 Dodge intrepid. Know for a fact that the original was rubber.

    That is one of my reasons for avoiding the RTV stuff.
  10. autox19

    autox19 True Classic

    East Lansing, Mi
    where was this thread last winter when I needed it? LOL This really clears up an issue I had sealing the thermostat housing on a honda. It wouldnt seal. I tried multiple times. I know see that my flawed logic has me using too much and/or clamping down immediately. This would explain why my Mechanic friend, who re-did it while I was at work, could get it to seal. He know what he was doing!

  11. Rupunzell

    Rupunzell Bernice Loui

    RTV is OK, problem when most folks use it, far too much is applied causing the excessive RTV to extrude or more often than not dribble into the internals which can be no problem to serious problems. There has been more than one engine that had their oil passages plugged up causing oil starvation and bearing failure. More is really not better.

    Hylomar was originally a Rolls Royce Aero engine gasket dressing. It does not cure hard and has the ability to re-seal. It will not dry-cure into gobs that can cause problems. Know there are more than a few brands of Hylomar today as the formula has become mostly public and it's variants might not perform in the same say as the original specification Hylomar. Suggest using the Hylomar PL32M (medium viscosity, comes in light and heavy) Aerograde. Here is short on Hylomar:

    -Re-torquing of assemblies using Hylomar might be needed due to compression settling of the Hylomar and gasket involved.

    Loctite 518 Anaerobic sealer and similar has been used in a LOT of modern industries from Auto to Aerospace to Ships to Industrial plant machinery and plumbing and more. Again more is not better, but similar to Hylomar there is less risk of hardened gobs of Anaerobic sealer drying-curing into problem causing gobs. Saab-Scania used this variety of sealer on the B204-B234 oil pan and more. For the oil pan, apply a thin layer, install the oil pan to the block then torque the screws to spec. Allow initial set for a few minutes, then re-torque as a check to see if any settling has occurred. Once checked do not disturb the assembly, it is essentially done and ready for service.

    These are the basic three used in the shop. Specific application determines which to use.

    Last edited: May 1, 2018
  12. Rupunzell

    Rupunzell Bernice Loui

  13. B0b

    B0b Daily Driver

    Has anyone had any experience ( or opinion) about eliminating the cam housing to head gasket in favor of using Loctite 518 or 574?
    While it will make future disassembly more difficult, these anearobic products work great in sealing Porsche engine cases, and the cam housing to head joints.
  14. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    I know that type of sealant has been successfully used on X transmissions, but I don't recall it being tried on the cam box. Keep in mind the thickness of that joint affects the valve clearances, so you would have to be pretty precise on its application and readjust the clearances after. While I've never been a fan of using sealants in general, it might help with the common leaks these engines tend to have. Now I'm waiting for replies saying they have never had any leak on any of their engines...there's always at least one. :D
  15. It could be useful for small base circle cams.
  16. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    And I should have mentioned, back when I last spoke to my Henkel rep (makers of Loctite products) he recommended 518 for this type of application. I was asking specifically about front wheel drive transmissions, motorcycle engine cases, air cooled Porsche engines, etc, but it would be the same for your intended use. ThreeBond has a similar product that's been very popular for such uses for many years.
  17. B0b

    B0b Daily Driver

    The joint winds up essentially metal to metal - there is no measureable thickness of 518 between the faces, unlike with RTV and the like.
    It would reduce the shim thickness 0.3mm - not enough to compensate for a small base circle cam but in the right direction.
    I like the anaerobic sealants as there is no issue with sqeezeout setting up, coming loose, and winding up in oil galleries. Any squeezeout stays liquid and washes away.
    One downside is that one would want to be pretty sure it doesn't have to come apart too soon, because cleanup is a bit of a pain.
    Thinking about.it/
  18. Yves

    Yves True Classic

    Great subject initiate by Paul.
    PDF documents from Henkel/Loctite, which products to use and how.

    Attached Files:

  19. myronx19

    myronx19 True Classic

    Toronto, ON Canada
    I love this stuff - it's expensive, but it really works. You can put parts into service immediately. I use it here in our lab at work (I work in Powertrain/Transmission development, and we use this stuff on all our transmission dyno equipment, and experimental devices under test - even works very well with automatic transmission fluid)

    Worth every penny.

  20. Dr.Jeff

    Dr.Jeff True Classic

    Sin City
    Myron, the pic isn't showing for me. What product are you referring to?

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