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Rtv on a head gasket?


NAXJA Forum User
Pacific N.W.
The instructions on my new gasket says it doesnt need any. Should i use some just to be safe? I have some hi temp black...think its ultra,(whatever that means) will this work or should i buy copper? thanks again guys
NO!!! You don't ever want to use a sealant like rtv on a cyl head gasket. make sure your cyl head and block deck are smooth and clean and put the gasket on by itself.
don't use any type of sealer on a head gasket. They are teflon coated, thats all they need. make sure surfaces are clean and dry. Also lubricate your head bolts so that you get accurate torque readings
I use Copper Coat on my head gaskets and have for decades It also is great for intake/exhaust gasket sealing.

It ought to have the sealant built-in. It looks like little orange-ish lines running all over it. According to the manufacturer, thats all you need. I didnt use any sealant a few months back on mine and it doesnt leak. Anymore :)

Ditto on scraping the surfaces throughly...Any old particulate will cause non-sealing and therefore another leak. If you do it all the right way, clean it, put the gasket on, hover over the engine with one foot placed stratigiclly...whereever, and the other on the radiator area,...and dont gouge the gasket when placing it back on, then tourquing the head bolts (NEW BOLTS ARE A SAFE ROUTE, i re-used mine but i marked them as having been on thier second life)
in the correct order, then you should be okay. And if you bend a lifter rod, get a hammer :doh:
Newer type gaskets do not require any type of sealer nor is it advised. Depending upon the application, many gaskets have silicone sealer paths printed on them or a sealer mixed into the gasket which is heat activated. Additional sealers on these gaskets may interfere with the sealing process.
99.9 % of the time I go with manufacture recommendation. Net Vodo is a poor reason to go contrary to the people that made the part in the first place. As long as said part is being used as intended. If it's not, all bets are off.
Strangely enough subaru and chrysler 4 bangers like a thin coat of spray on high tack. They use laminated steel gaskets though.I would never think of it on my sbc or 4 leaker.
Stick with what it says on the included instructions.

Speaking of gaskets and silicone, how many here have been rtv'ing water pump/thermostat gaskets? I was recently educated that about the only thing that's good for is sticking the gasket in place. After a while (6 months?)the rtv separates from the paper doing you no good.
RTV, Gasket Dressings, Gasket Maker in combination with a flat gasket, etc. All have their advantages and disadvantages, we can argue all day whether its better to use them instead or with a gasket.

EXCEPT a HEADGASKET. That is the most stressed and critical gasket of the whole motor. Not to mention, the most expensive and difficult job to replace if you screw up the job.

Now years ago, when headgaskets were all flat metal spring steel gaskets, Copper Spray and some other sealants developed help improve the seal etc. But over the years, they have drastically changed the Headgasket designs, using all sorts of different exotic materials intended for all sorts of different factors in sealing the head to the block. A lot of the new Multi-Layer Steel (MLS) Headgaskets are coated with a Neoprene Rubber Layer to act as a fill for surface imperfections in a far better way than any spray or squeeze on sealant will, the extra sealant would only defeat the purpose of that coating and most likely make it more likely the gasket will leak.

When I did the HG on my little Neon R/T, the instructions specifically recommended a special spray on Sealant by Part Number. I used what was recommended and it was different than any spray on sealant material that I've ever used, but it worked great and was specifically designed for my MLS Headgasket.

Although the Copper Spray Sealant is great in hi-temp environments with lots of pressure on the flanges (I use it on Exhaust Gaskets all the time) I wouldn't use it, UNLESS YOU KNOW IT IS COMPATIBLE AND WORKS WITH THE HEAD GASKET AND NOT AGAINST IT.

Unless you know better, from real knowledge, NOT just guess on your part; I'd follow the manufacturer's instruction to the letter. Use only the sealants they recommend, if they recommend NOT to use any sealants, than follow those instructions.

You don't know better than the guys that spent a lot of time and engineering to come up with that headgasket. Its just to tough of a job to re-do because you think you have a better idea.
In simple - No.

You can use a copper spray if you like (and you'll likely get good results,) but head gaskets to-day are generally built to be used with no additional sealer of any sort.

Also, using RTV will screw up clearances, and the RTV could burn out, which will cause a head gasket failure.

I haven't use a sealant of any sort on a "newer" engine - the last time I used a sealer was on a 1943 International inline six (which used a stamped steel shim for a head gasket, and it needed a little something...)

To clean the surface, use something akin to Scotch-Brite "Rolon" disks in a drill motor. You can't get the surface "too clean" - but you can damn sure get it "too smooth" - and I find a medium Scotch-Brite pad gives an excellent finish for head gasket sealing.

If you can't find Rolon discs locally, you can use a hand pad - use a circular motion and even pressure, and be sure to cover the whole surface of both the head and block.
Jon, it's Roloc, not Rolon. Be advised those little critters have knocked the bearings out of many an engine in hurried hands. Something about grit in the oil..
JJacobs said:
Jon, it's Roloc, not Rolon. Be advised those little critters have knocked the bearings out of many an engine in hurried hands. Something about grit in the oil..

Oh. It's been a long day - the kind where you spend the day thinking, "Something tells me I shoulda stood in bed..." Shot right to Hell before I went to bed last night, and I've been running around since I got up. Ugh.

I suppose it's possible to get grit in the oil if you're in a hurry, but I stopped being in a hurry a LONG time ago, and a head gasket is something you shouldn't be in a hurry to get done anyhow. Even taking your time, you can get one done on an XJ 4.0 in about a day, including ancillary inspections, clean-up work, and the like (I've done it twice.)

But yeah, don't get in a hurry. The "grit" is probably composed of pad particles, the small bit of removed material, and gasket detritus - which is why I flush everything down with carburettor cleaner while I've got it open, then change the oil (unless I'm dropping the pan as well, I typically leave an oil change for after assembly - carries more of the crud out with it that way.)