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How does Anaerobic sealant work?

52K views 16 replies 11 participants last post by  Twinsen 
#1 ·
Yes its a dumb question, but this is an educational forum, right? How does anaerobic sealant work? I understand that "anaerobic" means the sealant dries without air. But why is it so important to use this on my Timing cover?

Background: I'm wrapping up my headgasket/Timing chain/waterpump replacement. I replaced both timing chain & balance shaft chain along with applicable guides. My saab engine manual says to use anaerobic sealant when reassembling the timing cover (its a lot of fun trying to find this stuff). So I used it, and torqued the timing cover bolts to spec. Some of the excess sealant sqeezed out of the cracks (I neglected to wipe if off immediately). We came back to work on the car 3 days later, and the excess sealant that squeezed out was still soft (ie. it never hardened). I wiped it off, and pry that this stuff works.

can anyone shed any light on how anaerobic sealent is supposed to work since it doesn't seem to harden?
 
#2 ·
Don't know why SAAB wants to use something that exotic. I have used Permatex blue, the stuff SAAB calls for the sump pan, and later I used Permatex orange. They both work fine for me.

Does the inside of timing cover works under absolute vacuum? I don't think so. Sorry I can't give you an answer because I never used it. But I do know there are alternatives that work.
 
#3 ·
This is how I know it.
"anaerobic" means "no breath" or something like that in ancient greek. This means that the sealant need absence of air to harden. Lack of air is found when two mechanical parts are pressed one against the other, like a cam cover and a head when they're torqued down. So, the sealant that is squeezed out is still contacting with air, which makes it impossible for it to harden. But don't worry, the sealant that stayed at its place is definately hard now.;)
AFAIK many thread lock compounds work this way.
 
#4 ·
Jamal Bryant said:
Yes its a dumb question, but this is an educational forum, right? How does anaerobic sealant work? I understand that "anaerobic" means the sealant dries without air. But why is it so important to use this on my Timing cover?

Background: I'm wrapping up my headgasket/Timing chain/waterpump replacement. I replaced both timing chain & balance shaft chain along with applicable guides. My saab engine manual says to use anaerobic sealant when reassembling the timing cover (its a lot of fun trying to find this stuff). So I used it, and torqued the timing cover bolts to spec. Some of the excess sealant sqeezed out of the cracks (I neglected to wipe if off immediately). We came back to work on the car 3 days later, and the excess sealant that squeezed out was still soft (ie. it never hardened). I wiped it off, and pry that this stuff works.

can anyone shed any light on how anaerobic sealent is supposed to work since it doesn't seem to harden?
It does harden, just only in the absence of o2. Where it seems the atmoshpere (i.e. - where you wiped it off) it doesn't dry. When the two parts being sealed come into contact, and air no longer gets to the sealant, it cures.

One caution, don't partially torque a piece down if using anaerobics and come back to it, it will not torque the rest of the way down properly.
 
#5 · (Edited)
Anaerobic sealer has several advantages. It doesn't leave hardened strings of RTV that have squeezed out of the joints. It will cure, adhere, and seal even if there are traces of oil left on the joint or constantly leaking onto the joint (sump). It has much greater adhesion than RTV.
Loctite 510 hardens and is specified for rigid. doweled joints such as the Transmision Case.
Loctite 518 cures to a "hard rubber" consistency and is specified for those joints, like the Timing Cover, that flex because of the unequal expansion rates of Cast Iron (the Block) and Aluminum (the Cover).
RTV will work just as well if the surface is perfectly clean and dry. Loctite 518 is more forgiving.

AFAIK many thread lock compounds work this way
.
AFAIK, they all do.
 
#6 ·
Thank-you all for the explanation. I used Locktite 518 on my timing cover. And I did touque it to spec when applied. Was not easy to find Locktite 518 as Advanced Auto & Autozone don't seem to carry it. I ordered it from Summit Racing incase someone else has problems.
 
#7 ·
yaofeng said:
Don't know why SAAB wants to use something that exotic. I have used Permatex blue, the stuff SAAB calls for the sump pan, and later I used Permatex orange. They both work fine for me.

Does the inside of timing cover works under absolute vacuum? I don't think so. Sorry I can't give you an answer because I never used it. But I do know there are alternatives that work.
Saab say to use the anerobic sealant on basically all the engines surfaces, never RTV sealant
 
#8 ·
L4staero said:
Saab say to use the anerobic sealant on basically all the engines surfaces, never RTV sealant
That is not true. SAAB says to use Permatex blue (RTV) on the sump pan and anerobic sealant on the timing cover. This is from the basic engine shop manual.
 
#10 ·
Next dumb question: my smart-alec buddy helping with this project wants to know this:

If anaerobic sealant dries without air (cure in the abscence of air) they why doens't it dry out sitting in the tube?

My only explanation is that there must be air in the tube (at least it feels like 1/2 the tube is filled with air). Thoughts?
 
#11 ·
You have the correct explanation. Loc-Tite products used to note on the label (and may still) that the air space must be maintained to prevent hardening.
Since my employer bought the stuff, I felt compelled to try:
If you squeeze all the air out of a tube or bottle (we bought the big bottles), the material will harden. It will also harden if you put a drop on the bench and seal it off from the atmosphere with a glob of grease. Squirting oil on it is not enough to make it cure, it seemed that any exposure to air prevented curing.
 
#13 · (Edited)
The other side of the argument is that if you use RTV in an area where no air gets to it the product will not harden. For example, if RTV is used for the old felt gaskets that where packed into rear main seals the RTV might not cure properly because it just went basically back into the tube it came out of.
 
#15 ·
So as I read this Loctite 518 is the recommended sealant for the timing chain cover and the sump. I am just about to reassemble a 93 9000 griffin I bought with head, sump and timing cover off.
 
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