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Thread: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

  1. #1
    Official SM Expert: Motor Oil, Lubricants & Filtration
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    Exclamation Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    For you folks that have been on this site for a while, you know I’m a pretty big advocate of never using a spray sealer on a new MHG. I’ve based my argument against using it mostly on the various manufacturers recommendations…none recommend using a spray sealer. I’ve also used these two articles on surfacing the head and installing MHGs:

    http://www.aa1car.com/library/2003/eb30320.htm

    and

    http://www.babcox.com/editorial/ar/eb70228.htm

    My contention has always been: You want to have a MHG seal correctly? The RA spec (or smoother) for the specific MHG must be met for both the block and head, the machine work must be precisely flat for both the block and head, and the proper torque spec for the fastener used must be applied in the TRSM sequence. Attention to detail on these is what ensures a proper seal.

    I have also said (several times) that the use of a spray sealer (such as Permatex Copper, Brake Quiet, etc.) can damage the fluoroelastomer coating the MHG manufacturers use on their product. However, I've never really backed it up other than a single line in the first article. I decided to research this...first a little background:

    Viton (by DuPont) is the most common fluoroelastomer coating; it is used to initiate the initial cold seal on a MHG. It is applied in a very thin layer and is an inert, tough, heat resistant coating. It is one of the more expensive fluoroelastomers out there, and actually is manufactured in four families…the one we are interested in is for automotive applications. It is highly resistant to oil, gasoline, nitro methane, and alcohol. However there are certain chemicals that will affect it. From a tech article on Viton:

    “In general, low molecular weight ketones and esters will swell a vulcanizate of Viton and, in fact, ketones such as methyl ethyl ketones are used as solvents for uncured Viton®. Esters such as ethyl acetate are also used as solvents for Viton. The more polar a material the more likely it will swell Viton. Much work is being done in the area of solubility parameters to characterize the swelling behavior of various fluids by comparison of dispersion, hydrogen bonding and dipole parameters to the corresponding parameters of the elastomer.

    Amines affect Viton® differently from the ketones and esters. Generally, amines will react with the polymer backbone and result in embrittlement of the vulcanizate. The elongation will drop off significantly and hardness will increase. Amines are just one kind of base. In general, strong bases such as sodium hydroxide at relatively high concentrations will degrade Viton®. In summary, a basic understanding of chemistry is helpful in judging an elastomer's resistance to swelling or degradation.”


    Now...the question is are any of these chemicals in a spray sealer? If you read the back of a can of Permatex Copper Spray-a-Gasket, it contains methylene chloride (a simple chlorohydrocarbon), acetone (a ketone), and ethyl acetate (an ester). Take another look at the tech article quote above…since acetone is a ketone, it will attack Viton. I have personally used acetone to clean the old Viton off in order to re-use a MHG. Ethyl acetate is specifically mentioned above as a solvent for Viton...I do believe we have the culprit Dr. Watson! Acetone and ethyl acetate can cause Viton to swell, making its ability to seal very questionable.

    The most common counter I hear for using a spray sealer is “I’ve always used it and never had a problem”. That’s fine…use it if you want, but realize that you are applying chemicals that can dissolve the fluoroelastomer coating designed and engineered for the MHG you are using.

    I also hear “Cometic says it’s not required, not that it’s not recommended”. Well, I called Cometic and spoke to one of their engineers…his response was “our gaskets do not need additional sealer…we do not recommend using it.” Using a little common sense and knowing how the chemicals in a spray sealer affect Viton, it’s no wonder they do not recommend it. BTW…I couldn’t get HKS to talk to me

    Everyone here is free to make their choice. After reading up on the chemistry, I’m not going to use a spray sealer regardless who says it’s ok. Chemistry does not lie...this is not based on hearsay. I’m pretty positive the engineers know what they are doing on this one
    I will no longer respond to tech questions via PM. If you have a question, put it on the forum so everyone benefits from the answer.

    Quote Originally Posted by Supracentral
    However I still stand by my statement that 99 times out of 100, the weak link in the MKIII is the owner.
    Quote Originally Posted by jetjock
    I swear, it's like talking to an amoeba...


    Want to know about oil...read this:
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    What you do today, might Burn Your Ass Tomorrow"

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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    good info JOHN!

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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    i vote this should be stickied!!!

    +1 to you sir

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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    Quote Originally Posted by jdub
    BTW…I couldn’t get HKS to talk to me
    Just to add to this,(and a little off topic) when I was having my motor built I was having an HKS MHG installed, I wanted the info from the horses mouth on what RA was needed for their stopper MHG, so I called them. The tech I talked to told me that a stock RA was all that was needed for the stopper as it has a layer of black sealer on the gasket for this purpose.

  5. #5
    toonar

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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    fluoroelastomer coating

    thats a fancy word! thats the suede/wetsuit feeling on a new mhg eh?

    i was told by Reg to go for 25-30 RA for the gaskets. ever done lapping by hand? not a ton of fun. i had wanted to get a surface profilometer to test RA until i found out how much they were.
    he had also told me if you go into the machine shop and ask for a specific RA and they look at you like you're insane, go elsewhere.

  6. #6
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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    John is so smart!!!!!





    Great article, and very well written................lol

    FEAR A GOVERNMENT THAT FEARS YOUR GUN

    http://www.break.com/index/one-of-th...-made-2218472#

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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    Quote Originally Posted by suprahero
    John is so smart!!!!!





    Great article, and very well written................lol

    ^^ i agree

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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    Great Info!
    For fyi; Does anyone have a list of the chemical content in Brake Quiet?
    Since that has been widely talked about as an alternative sealant for MHG.

  9. #9
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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    Thanks guys...but, I'm not that smart

    I just like to know how things work. You can research almost anything fairly easy now-and-days and knowing how a machine (or a Supra) works gives you a better understanding of what to do and how to do it if you have a problem. It's really not rocket science.

    I got trained in the Air Force on the flying game...we were taught to question and seek as much information possible on how to get better at what we did. That's carried over with me for many years...especially dealing with machines I happen to be in control of. One concept that really stuck was there are Rules and there are Laws: Rules are basically regulations, they can be bent or broken. You may get yourself in hot water, but you're gonna walk away and have a beer with the guys later. Then there are Laws...these are based on hard science (physics, chemistry, etc). You break a Law and metal gets bent, things blow up, or even worse, your buddies are going to your funeral.

    It makes you take a good hard look at what you're doing...to me that's a healthy way of doing business. That's also why I take hearsay with a grain of salt...I want to see the facts a way of doing a task are based on. The good thing is there's an awful lot of information out there at your fingertips (especially with Google)...digging it out is really not that hard
    I will no longer respond to tech questions via PM. If you have a question, put it on the forum so everyone benefits from the answer.

    Quote Originally Posted by Supracentral
    However I still stand by my statement that 99 times out of 100, the weak link in the MKIII is the owner.
    Quote Originally Posted by jetjock
    I swear, it's like talking to an amoeba...


    Want to know about oil...read this:
    Motor Oil 101 - Dr AE Haas


    "Life is like a jar of Jalapeno Peppers
    What you do today, might Burn Your Ass Tomorrow"

  10. #10
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    Default Re: Thinking About Using Spray Sealer on a MHG?...Might Want to Read This

    I also vote for this thread to be stickied. This is information all of us should be aware of (because most of us will do the HG swap sometime or other as long as we own our supras ).

    Dbsupra90, if your getting you head AND block resurfaced and machined for RA, tell them to do the lowest RA they possibly can. Go even lower than 25 RA, because according to the first article, "smoother is better with MLS", and that's assuming you would be using a MLS HG, which you should.

    The ONLY time you would use a spray on sealer on a MHG is when you are reusing one, and even then you MUST MAKE SURE ALL THE OLD VITON IS OFF THE HEAD GASKET! That topic has been discussed before in previous threads.

    As far as the second article is concerned, a lot of the same material in this one is almost identical to the first (That must be ringing a bell in your all's heads. If both articles are quoting the same things, then they are most likely correct and factual information). The second article is a good ready also and goes in depth on many factors that cause head gasket failure and the preventative maintenance needed to solve these problems.

    Great find John! Keep it up, and if any mods are reading this, sticky it!

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