RTV Silicone Shelf Life

[Legacy777]

I started building my motor this weekend and have run into a possible issue. I used the recommended Subaru sealant, Threebond 1215 (pretty much same thing as Permatex Ultra Grey). However it is not hardening up. I bought the sealant back in 2005 when I built the first motor. It has set inside my house for about five years.

 

I'm not sure if there's a shelf life for RTV silicone, or if it will harden up with more time. It got a little harder over night, but is still soft. I've got a plate with some blobs sitting outside in the sun to see if heat may help.

 

I'd hate to pull the short block apart, but I certainly wouldn't want the damn thing to start leaking on me.

 

Any thoughts or suggestions are welcome.

 

Thanks

 

PS: Here's some pics of the build

Piston Ring Sizing

Short Block Assembly

[The Dude]

Perhaps there is someone on this board with more experience with Threebond 1225. However, I use use RTV frequently in my business. After a period of time it seems to get "gummy". Once it reaches that state it will NOT harden properly. Leaks are a problem, but pieces of RTV are often responsbile for engine failure due to oil starvation. Apparently. small pieces of RTV are great at clogging up oil passages.

 

If the RTV hsn't cured in a couple of hours, it's probably gone bad. Personally, I would not take a risk with my engine. One again, maybe someone has experience specifically with Threebond 1225.

[GeneralDisorder]

Threebond is different - it's designed not to clog oil passages and as such I beleive it hardens much slower. It's not really like RTV at all though many people do use RTV in it's place.

 

RTV stands for "room temperature vulcanizing" - the only way it goes bad is to harden in the tube..... same with the Threebond stuff - if it's not hard when it comes out of the tube then it's still good.

 

My preference for the case halves is Loctite 518 - it's a flange sealant and is very good stuff.

 

GD

[OB99W]

Josh, you're probably not going to like this, but the "official" shelf life for most RTV is 6-12 months. That doesn't mean it can't remain usable for a longer period -- I suspect that short period takes into account other time spent in stock, on dealer's shelves, storage at temps outside the recommended range, etc. -- but 5 years is asking an awful lot of it.

 

Oxime-cure RTV (Threebond 1215, Permatex Ultra Grey, and other "sensor safe", non-corrosive ones) are dependent on moisture in the air to cure (as are the acetoxy-cure RTVs that give off a vinegar-like [acetic acid] smell). RTVs designed for things like engine assembly have a cure that's slow enough to allow parts to be mated before surface "skinning" occurs. However, you should typically expect surface "drying" within an hour or so.

 

Up to a point, additional heat and humidity will accelerate things, but if the normal rubbery cure isn't reached within a couple of hours, the material probably has just gone bad. If that's the case, not only might the initial seal be questionable, but the oil resistance will likely be compromised as well.

[Legacy777]

Thanks for the comments everyone. That's what I kind of expected. I will likely split the case. I'm going to pull the oil pump and rear oil separator and see if they have hardened or not Depending on what I find will determine what I do with the case.

[Legacy777]

Specs from threebond say 12 months

 

http://www.nzgaskets.co.nz/pdfs/Threebond/1215.pdf

[GeneralDisorder]

I used to use a lot of Threebond where I worked (we manufactured/serviced Kobelco oil-free rotory screw compressors) and I know we had some sitting around the shop for a lot of years (rarely needed it actually since most air-end failures went back to Japan for core value) and we never had an issue with it. My experience was always that if the tube were sealed well and the stuff wasn't partially or completely cured - it worked fine. We never paid any attention to "shelf life" and I doubt my shop foreman even knows it has one (though I'll ask him about him when I see him which is every few days typically).

 

From what I have seen, the Threebond has a different consistency and different dry texture than ultra grey. We were specifically warned AGAINST using RTV as it can clog oil passages in the machines we were using it on - Threebond did not.

 

GD

[Legacy777]

Well it's "hardening" up more as it sits, but it's still not the same consistancy as it was before.

 

We'll see if it continues to harden...

[idosubaru]

is Threebond anaerobic sealant?

 

i'm a weirdo who always goes with subaru's recommendation of using anaerobic sealant on engines. it doesn't dry ANYTHING like RTV. i don't know how it works but every time i use it (case halves, cam carriers, oil pumps...etc) it remains much different consistency. it *seems* like it's not drying at all. but somehow it always holds.

 

external bits will smear and remain a playdoh like...sort of consistency..not quite like that either. anyway, it's always done that and always worked. so if Threebond is an anaerobic or possibly nothing like RTV at all i suspect it might be normal.

 

i would be surprised if shelf life is an issue myself.

[OB99W]

Threebond 1215 is not an anaerobic sealant -- it is silicone based, oxime-cure type (RTV).

See: http://www.threebond.co.jp/en/product/series/sealants/1200list.html

 

RTVs can definitely deteriorate with extended storage. They last longer in the original sealed container, especially if the temperature isn't excessive. If you happen to buy it shortly after the dealer gets delivery of fresh stock, and treat it well, the shelf life will probably be considerably longer than the 12 month "spec". However, Josh said his was from 2005, and with RTV that old, proper curing is hit-or-miss.

 

If anyone thinks that RTV doesn't have a limited shelf lfe, I suggest you read the FAQs at websites of companies that make the stuff. If you've never experienced RTV that didn't cure, consider yourself lucky.

 

I've gotten "bitten" more than once by RTV (and epoxy) that didn't set up. In one case, the RTV was well within the allowed shelf life, so either it was exposed to high temps for too long before I got it, or it was just a badly formulated batch. Since cleaning up uncured material is such a pain, I now make it a point to put a small amount on a piece of paper and make sure it cures correctly before using the rest on a job.

[Legacy777]

I called and talked with an engineer at threebond today. He gave the 12 month shelf life expentancy as well. I decided to bite the bullet and split the halves to redo it for piece of mind.

 

I did get them to send me the MSDS for the 1215....it sounds like nasty stuff after reading the MSDS.

[GeneralDisorder]

I did get them to send me the MSDS for the 1215....it sounds like nasty stuff after reading the MSDS.

 

Most MSDS sheets make it sound like openeing the container might cause a city-wide evactuation to be called for. . Just don't eat it or smear it on any exposed mucus membranes and I think you'll be aright to still have kids .

 

I've used MUCH nastier stuff than some RTV and I'm still standing (most days ).

 

There's an MSDS floating around out there for Water - no kidding. I don't beleive it's officially recognized (by the EPA, etc) but on the commercial side of things lots of companies want one on file just for the sake of being totally anal about having every chemical in the facility in the MSDS drawer.

 

This is very interesting BTW - I have never experienced bad RTV (other than partially or fully cured due to tube fail). I'll have to pay more attention to that stuff from now on.

 

Might I sugest you go with Loctite 518 on the case halves instead - it's an excelent product for flange sealing.

 

GD

Edited September 7, 2010 by GeneralDisorder

[OB99W]

I've used MUCH nastier stuff than some RTV and I'm still standing (most days ).

Me too. One of my least favorites (at minimum, from the stench aspect) is 2-part polyester filler, commonly known to many by the brand name "Bondo". See MSDS http://www.plasticareinc.com/Merchant2/MSDS_Bondo/bondo%20body%20filler%20264.pdf

 

Note that repeated overexposure to the stuff might mean that you can't have kids ("reproductive organ damage").

Edited September 7, 2010 by OB99W

[GeneralDisorder]

I think the worst thing that has come into my purview from an "odor" aspect is Ammonia - I used to work on pumps and it was (to some extent) the responsibility of the customer to flush them prior to sending them in - we would have them sign release documents to that effect before we would touch them. Well, as you can imagine, there is often a disconnect between the guy signing our form and the monkey in overalls that's supposed to have done the actual work. I remember on one occasion where a pump of this sort was openened up on the shop floor (mind you - this is a warehouse sized facility with 30' ceilings, exhaust fans, 20' bay doors, etc) and it cleared the building within secconds. The Ammonia was so strong you couldn't breath and we all took to running for the doors. That stuff will straight KILL you dead if you aren't careful with it. I can see now why they don't run ammonia in air conditioners except in the largest, most commercial or industrial settings where it can be carefully controlled and monitored. . Masks that filter it out are expensive too - difficult to work around.

 

Beyond that - as far as straight hazardous stuff - I've had to work on vacuum pumps that provide hospital surgical suction as well as dental office pumps for the same use. Also pumps used to remove the flamable methane from large septic reserviors. I had to do the whole dissasembly, inspection, and cleaning in hazmat gear (somtimes with the ambient temp well into the 90's). Talk about making the process more difficult . Never got sick from and for that I'm thankful for the gear my employer supplied.

 

I know some of the aluminium cleaning chems are really nasty too. Basically acid-based strippers and such. They will burn your skin so I'm assuming from that reaction alone they are fairly high on the scale of nastiness .

 

GD

[Legacy777]

Well....interestingly enough. I went to check things this afternoon. I was going to pull the separator plate off and check things. The silcone seems pretty much near its normal hardness. It is very humid down here due to the tropical storm being near by. So the extra moisture in the air may have helped in curing the silicone. I've got a new tube and some gaskets on order. I will likely let it sit throughout the week, and do a test blob of the new tube and the old tube that has sat for the week and see how they compare.

[Legacy777]

I split the motor on Saturday. There were areas where the silicone had not cured. I'm glad I took it apart, despite spending about 10 hours disassembling and cleaning everything so it's ready to go back together. We'll try putting together again next weekend.