Mike kZ Posted March 21, 2002 Share Posted March 21, 2002 I do remember a repair kit for cast iron that just used a propaine tourch for heat with some special welding rods. I can't remember the name. Try searching the web. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 21, 2002 Share Posted March 21, 2002 Take it to a professional to weld with the correct rod. The cast iron needs to be thoroughly heated before welding to keep it from cracking.. I do not think JB Weld will hold onto that kind of temperature. I used JB Weld on an aluminum cylinder head that held for about 2 years but does not get that hot.The POR 15 people make a FIRE SEAL 2000 product to repair cast iron manifolds but I have no experience with it 1-800-457-6715 for a dealer. It will cost about the same to doctor it up than to get a professional to weld it Quote Link to comment Share on other sites More sharing options...
Peternell Posted March 21, 2002 Share Posted March 21, 2002 I had to get a marine manifold repaired due to freeze cracks. New ones were $300 each so $40 at a local welding shop seem to be a deal. They heated up to 300 degrees for several hours, then welded it. Didn't see the process just the finished product and a very reasonable bill. Quote Link to comment Share on other sites More sharing options...
denny411 Posted March 21, 2002 Share Posted March 21, 2002 I have had good success in the past with brazing exhaust manifolds. The key is surface preparation and pre heating. first use a die grinder w/ a carbide cutter to cut at least an 1/8" deep groove in the full length of the crack.I heat the entire area surrounding the crack red hot with a torch.while it`s still hot I use an air hammer with a sharp pointed bit to chip the entire area,putting small punch marks all over the area to be brazed. As a manifold ages,a thin crust of rust forms over the surface.This chipping will remove the crust as well as creating a good "toothed" surface for the brass to adhere to.The heat helps to loosen the crust.Finally,Reheat as much of the area to red hot(and keep it red) as possible while brazing. One of the manifolds that I brazed this way has aquired over 25,000 mi so far with no problems at all. Yes it`s time consuming but If done correctly it will be a permanent repair and possibly stronger than new. Also... If at all possible try to clamp the manifold securely to minimize warping.I usually take them to a machine shop to have them resurfaced after brazing. Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted March 22, 2002 Share Posted March 22, 2002 I have a cracked exaust manifold on my 98 Frontier. Since Nissan wants almost $200 for a new one, they are non existant in junk yards, and no pre-made header is available, what are my options to repair it. My dad says I could weld it with a stick welder if I had a high nickel rod. I was wondering about something like JB Weld or some sort of epoxy. Could any of these stand up to that use, or am I stuck trying to find one. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 25, 2002 Share Posted March 25, 2002 ...not very many people can work on cast iron anymore....i'd look again for it from a salvage yard...on the net...i blew a big hole in a manifold on a 302 engine in dallas....couldnt find anyone who could fix it...saw a sign written on a paper box (welding)...found an old man that used to weld in the oil fields....he could do it...he had to heat it till it was red-hot (took a while)...i dont think brazing it will work well for very long...jb weld or epoxy is good on blocks but i dont think it will work well on exhaust.... i'd take (/send)it to a trade school if you can...its such a bitch to get on and off (and if it doesnt fit exactly right it'll be noisey)..i'd probably spend the $200...s Quote Link to comment Share on other sites More sharing options...
jeromio Posted March 25, 2002 Share Posted March 25, 2002 Perhaps I'm living in a world of blissful ignorance, but I've welded cast iron manifolds (and other items) several times using my mig welder. For instance, the manifold on my truck was totally shot - the flange was broken off and the entire bottom section of it had corroded away to nothing. I ground away the goobered parts and then welded it up. I did weld over about a 5 inch swath to make sure that things annealed and would be less likely to crack. It's held up now for about 5 months. Quote Link to comment Share on other sites More sharing options...
eugene Posted March 26, 2002 Share Posted March 26, 2002 Aaron, are you sure that is not under factory warranty? I believe exhaust is 5yr/60K. If you're close to that and cry enough the dealer can probably do a Goodwill warranty. Just a thought. We have replaced a lot of those manifolds at my dealer in Atlanta. If you remove it, soak it real, real good. The studs for the downpipe are bad about breaking. Quote Link to comment Share on other sites More sharing options...
Guest zthang43 Posted March 26, 2002 Share Posted March 26, 2002 yes, I have also welded the exhaust manifold on the 4.3 in my Z. I had to cut the flange off and move it inboard about 3/4" and re-weld it (otherwise it hit the frame). That was over 1.5 years ago, and no problems. I just used a mig welder and gobbed lots of filler on there. I haven't pulled it off to inspect it, but it definitely doesn't leak. What I would suggest, before you buy another manifold, is to try just welding up the one you have; you don't have much to lose by doing that except the pain of pulling it off again if it doesn't work. What I would do is use a die grinder to V the crack about halfway through the thickness of the casting (make sure to V it well past the visible ends of the crack) and then try welding in spots until the entire crack is covered and filled; giving it time to cool in between adjacent spots. That way you won't get the weld area too hot, and the shrinkage of the weld won't be as severe, which is what causes the cracking. This method of welding in spots in alternating places is used in body shops to weld on replacement sheet metal pieces. It prevents the sheet metal from shrinking due to heating/cooling. Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted March 26, 2002 Share Posted March 26, 2002 Jason, the warranty is actually 3yr/36k and I am at 80k+. I have been reminded that a guy that I go to church with had a welding shop. I am going to check with him first. If not, I will give the old MIG a try. Worst case, I have to buy a new one. On www.car-part.com all I found was 2 in CA at $175 ea, so I am better off getting a new one at the dealer. Thanks for your help guys. Quote Link to comment Share on other sites More sharing options...
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