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

jdub

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#1
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 ;)
 
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jimi87-t

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#4
jdub said:
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.
 

dbsupra90

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#5
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.
 

suprahero

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#6
John is so smart!!!!!





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

isnms

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#8
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.
 

jdub

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#9
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 ;)
 

starscream5000

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#10
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!
 

Clip

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#11
:dunno: who cares, its not like any of us blow head gaskets.

:biglaugh: just kidding, that is real good info. could we sticky this? thanks, John!
 

Boostedstr8six

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#12
So, if you are reusing a MHG or prefer brake quiet or copper sealer on a new gasket, remove the factory coating first. There isn't anything wrong with using the sprays after that.

Good info though.
 

Boostedstr8six

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#14
starscream5000 said:
The factory coating of Viton should be superior to any spray on sealer hands down. Why would you take that off?
I agree. I used the copper spray when I reused my MHG. Some people might prefer one of the sprays over the factory coating if they couldn't get good surface finishes and need to fill in deeper machine grooves.
 

The Reaper

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#15
well im not gonna get into it with jdub again cause last i got banned for a week for stating my opinion

but i used metal gasket sealer on my cometic mhg 8 months ago and nothing has happened yet ran 18 psi on a 60-1 for 3 months racing it 4 times a week and it still has no problems i dont see how it can screw anything up honestly

it is a spray on glue thats MADE for metal gaskets it was a copper spray, but to each their own i will not say anymore as i will prolly get banned again :icon_roll
 

jdub

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#16
The Reaper said:
well im not gonna get into it with jdub again cause last i got banned for a week for stating my opinion

but i used metal gasket sealer on my cometic mhg 8 months ago and nothing has happened yet ran 18 psi on a 60-1 for 3 months racing it 4 times a week and it still has no problems i dont see how it can screw anything up honestly

it is a spray on glue thats MADE for metal gaskets it was a copper spray, but to each their own i will not say anymore as i will prolly get banned again :icon_roll

You mean this thread:
http://www.supramania.com/forums/showthread.php?t=21566

The one where SupraCentral removed your obscenities & insults in post #25...the one where SupraCentral rolled it back for the same reasons in Post #42 in an effort to keep it civil.

You were not banned for expressing your opinion...nice try, but IMO you were banned for the reasons above. You can do as you wish...as I said then, and still say now, you're going affect the factory coating with chemicals that have an adverse effect. I'm sorry, but an emotional arguement based on hearsay doesn't work with me.
 

Nick M

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#17
Many people don't lock their doors at night, for years at a time. Therefore, it is ok to leave them unlocked all time.
 

starscream5000

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#18
Lol at your post #19 on that link John. I think it's like the second sentence or third. I don't think anyone caught it, unless it was a deleted post.
 

The Reaper

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#21
jdub said:
You mean this thread:
http://www.supramania.com/forums/showthread.php?t=21566

The one where SupraCentral removed your obscenities & insults in post #25...the one where SupraCentral rolled it back for the same reasons in Post #42 in an effort to keep it civil.

You were not banned for expressing your opinion...nice try, but IMO you were banned for the reasons above. You can do as you wish...as I said then, and still say now, you're going affect the factory coating with chemicals that have an adverse effect. I'm sorry, but an emotional arguement based on hearsay doesn't work with me.
ok whatever you say man

don't put gasket sealer on yur mhg it is bad i wouldn't recommend it at all!!!!

awesome information GO JDUB!!
 

Boost Lee

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#25
Going through a BHG right now....lol.

I like how you made it sound like I was diagnosed with a disease or something. :D

:eek3:

Well...I'm just putting everything together now.
 

starscream5000

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#26
Lol, I seen part of your "disease" on one of your friend's hoodies at the supra meet a couple of weeks back. I was like, "Hey, where's the Korean?" They were like, "He's got a BHG right now so he couldn't make it." He then comences to point out a big oil stain on his hoody and says, "Here's part of him right here." Then Suprahero said something like, "Yeah, we keep parts of our BHG buddies with us all the time."
 

Adjuster

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#27
The Greddy MHG I used had no viton coating. It had no coatings that I could see actually.

I've used this gasket now on 4 motors, and it's been clamped down 5 times. Four times we used brake quite, and one time we used hylomar, and none of the times has the gasket leaked at all.

This last time we actually clamped it between the tourqe plate and the block, then bored the motor and the gasket, then cleaned it all up again, coated it with brake quiet, and clamped it back in place again. (No problems so far.)

No idea what the RA is, but it was pretty smooth. I would not say mirror smooth, but you could not feel any machine marks, but you can see them. I belive the brake quiet does a great job of sealing up the small machine marks, and it's tough enough to hold up to boost and combustion pressures. We all know the metal head gasket is stronger than the composite ones, so they rarely ever distort unless there is crazy detonation. (At least in my experiance.)
 

jdub

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#28
Re-using a MHG with a spray coating is fine...it's when the viton is present there's a problem. Heck...using the spray on a composite HG is likely ok too ;)
 

Boost Lee

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#29
starscream5000 said:
Lol, I seen part of your "disease" on one of your friend's hoodies at the supra meet a couple of weeks back. I was like, "Hey, where's the Korean?" They were like, "He's got a BHG right now so he couldn't make it." He then comences to point out a big oil stain on his hoody and says, "Here's part of him right here." Then Suprahero said something like, "Yeah, we keep parts of our BHG buddies with us all the time."
"Here's part of him right here."

:rofl::biglaugh::rofl::biglaugh::rofl:

Back on Topic...

Hylomar Blue = looks & smells like silly string = Using Silly string to seal your HG works just fine..........right?

:rolleyes:
 

QWIKSTRIKE

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#30
jdub said:
Re-using a MHG with a spray coating is fine...it's when the viton is present there's a problem. Heck...using the spray on a composite HG is likely ok too ;)


Good info for the mentally challlenged builder, but it should read "thinking of using spray sealer on a new head gasket"!:naughty: :biglaugh:
 

darkspeed

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#31
I was curious if the copper spray was a good or bad idea. I went with it anyway.

I've been running 17psi for about 1.5 years on an upgraded ct26; no problems yet. But then again, with the T61 at 20 psi it may go to shit.

I wonder, since I let the copper spray tack for 30 minutes, maybe some of the solvent reducer in the spray dissipated; who knows.
 
D

drumminforev

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#32
Ok, no spray on mhg, got that.

What about on stock graphite head gasket? Just slap it on or should some sealer be used. Is there a certain RA spec for stock that needs to be met?
 

JustAnotherVictim

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#34
drumminforev said:
Ok, no spray on mhg, got that.

What about on stock graphite head gasket? Just slap it on or should some sealer be used. Is there a certain RA spec for stock that needs to be met?
No spray on a NEW mhg or one that still has Viton on it.
Stock needs nothing.
 
D

drumminforev

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#35
it doesnt need to be lapped or anything?

What type of cleaning substance should i use to get the bits of old hg off
 

GrimJack

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#36
Gasket remover will work fine for that. Clean up the block surface and the head, put on the new gasket, bolt it down and you should e good to go, just remember to torque Toyota bolts to 72 foot pounds, or if you're using ARPs use the specs they specify on the instruction insert.
 
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#37
I remember seing this one JDM option 2 video that they put RTV on a head gasket for a SR20DET?? the RTV's color was orange.. I dont know if it works good but they got the car running and used the car for drifting. maybe some JDM shit huh dont ya'llz think?

aite, peace.