FlyingMonkey Posted November 5, 2013 Report Share Posted November 5, 2013 I happened to notice yesterday that on the upper right side of my firewall there is a wire pass through hole where a large bundle of wires goes through (I think it's all the engine instrumentation wiring). The problem is the hole is as big as the length of my thumb and there is plenty of open space there. Seeing as the purpose of the firewall is to provide a gas-tight wall between the passengers and engine fumes, fires, etc, this seems...suboptimal. Should I get a tube of firewall sealant (IIRC Dow makes some amazing stuff that is rated for 2000°F for 20 minutes, but is $80 for 6oz) and seal this and any other holes I find? Is there some other procedure recommended by FD for these kinds of issues? Link to comment Share on other sites More sharing options...
Rich Posted November 5, 2013 Report Share Posted November 5, 2013 Andy, We just used some permatex high temp sealant two days ago (red in color) to re-seal an opening where the brake line went through the fire wall. The high temp permatex was the original seal that the dealer used for this purpose. It cost about $9 per tube at any auto parts store. Rich Link to comment Share on other sites More sharing options...
Rich Posted November 5, 2013 Report Share Posted November 5, 2013 Andy, I just called NAPA. It comes in a 3 oz. tube for $6.49 and is rated for 650*F. Rich Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 5, 2013 Author Report Share Posted November 5, 2013 I have some Permatex Copper, it's rated to 700, I guess I can just use that. Thanks Rich! Link to comment Share on other sites More sharing options...
sandpiper Posted November 5, 2013 Report Share Posted November 5, 2013 The RV-12 build plans call for ProSeal for sealing the fuel tank and the firewall. But, it is a messy 2 part concoction. Some have substituted various high temp. sealants. One builder actually did some testing. You could probably search www.vansairforce.com and find what worked best. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 5, 2013 Author Report Share Posted November 5, 2013 Here is the stuff I was talking about, it's milspec and used by Boeing and a lot of other big builders http://www.skygeek.com/prc-desoto-ps-700-firewall-sealant-6-oz.html Link to comment Share on other sites More sharing options...
Tom Baker Posted November 5, 2013 Report Share Posted November 5, 2013 Is the hole just in the firewall blanket or both the blanket and firewall? Link to comment Share on other sites More sharing options...
Anticept Posted November 5, 2013 Report Share Posted November 5, 2013 Morden, The area you refer to is indeed the primary wire bundle. is it as big around as your thumb, or is it some big oval shape (long as your thumb, as you said)? Also, putting very high temp stuff there is a waste. Epoxy turns soft after a couple hundred degrees Fahrenheit, and mush after that. If that high temp stuff melts, your engine has already fallen off. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted November 5, 2013 Report Share Posted November 5, 2013 Andy, I bet your airplane didn't deliver new with a firewall blanket. If that is the case the installed, upgraded blanket probably meets some specification or bulletin or something. I would find the paperwork that instituted the blanket retrofit and comply with it. Link to comment Share on other sites More sharing options...
Roger Lee Posted November 6, 2013 Report Share Posted November 6, 2013 You can use the high temp RTV. That is what was supposed to have been added around items that go through the firewall to seal it. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 6, 2013 Author Report Share Posted November 6, 2013 Below is a pic of the hole from behind the instrument panel. The light coming through is daylight (cowl was off). If it was a pinhole I'd ignore it, but this is pretty big. Not only is fire a hazard, but I'm afraid of CO infiltration if I develop an exhaust leak... Link to comment Share on other sites More sharing options...
mocfly Posted November 6, 2013 Report Share Posted November 6, 2013 Wow. Wouldn't it be better to disconnect the wires put them thru some fire sleeve and then seal up the edges of the sleeve? This way if you need you can always pull another wire thru the sleeve? Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 6, 2013 Author Report Share Posted November 6, 2013 The bundle is fire sleeved on the other side. Maybe I will cut a piece of fire sleeve and wrap around the wires and then seal up against that with RTV. Or I could flatten a piece of fire sleeve out and make a "patch" over the inside and seal that in place around the hole. Link to comment Share on other sites More sharing options...
mocfly Posted November 6, 2013 Report Share Posted November 6, 2013 That may work, but I would defer to the pro's on the site Link to comment Share on other sites More sharing options...
Roger Lee Posted November 6, 2013 Report Share Posted November 6, 2013 The fire sleeve around the wires should go into the hole. If need be work it in with a screwdriver. Then use the RTV to seal the fire sleeve in place on the fire wall. p.s. If you have the black plastic instead of the fire sleeve that to should go into the hole and be sealed. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 6, 2013 Author Report Share Posted November 6, 2013 Thanks Roger. Link to comment Share on other sites More sharing options...
Roger Lee Posted November 6, 2013 Report Share Posted November 6, 2013 p.s. If you can't get the fire sleeve back in the hole it's no big deal. Make the hole bigger. I don't try and squish the fire sleeve too flat because I can't ever get wires in or out any more. It needs to be a conduit so leave yourself some room. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 6, 2013 Author Report Share Posted November 6, 2013 If the fire sleeve is too short to go back in the hole, can I take another piece of sleeve, cut it, and wrap it around the remaining section of wires and put that through the hole, securing with wire or cable ties and RTV on the joint? Or will I need to pull the old sleeve off and put a new longer sleeve on? Link to comment Share on other sites More sharing options...
Roger Lee Posted November 6, 2013 Report Share Posted November 6, 2013 There only needs to be the fire sleeve in the hole. Any thing on the engine side doesn't matter for length. Most fire sleeve conduits go up to the air intake between cyl. 1&3. You could do it your way if you wanted, but I haven'r seen one that it was necessary to do it to. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted November 6, 2013 Author Report Share Posted November 6, 2013 There only needs to be the fire sleeve in the hole. Any thing on the engine side doesn't matter for length. Most fire sleeve conduits go up to the air intake between cyl. 1&3. You could do it your way if you wanted, but I haven'r seen one that it was necessary to do it to. Cool, I'll just move the sleeve up on the wire bundle until it fits through the hole. Thanks for the help! Link to comment Share on other sites More sharing options...
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