Exhaust manifold crack - braze or ??

[dstig1]

I prefer posting my welding questions here vs WeldingWeb as the atmosphere is much friendlier here... I have an older Honda civic 1998 that I found has a cracked exhaust manifold. It appears to be a very common problem. See pic. Given 193k miles on the car, I don't want to spend a ton. I may even just not fix it, but I think I should. I really don't want to replace it as the exhaust manifold also incorporates the catalyst (brilliant!). Welding cast iron is way beyond my skill level, but I figure brazing should work. Problem is my brazing is limited to one try in a class 18 yrs ago on steel sheet metal. So the questions are obvious. Is brazing OK for a very hot item like a cast iron exhaust manifold? What filler/size to use? And then furthermore, I have an oxy/propane cutting torch. I believe I can braze though not weld with a brazing tip (need to buy one). True/false? Suggestion from a friend was to buy a random scrap manifold from a boneyard to practice on (sounds like a good idea) and then do this in place on the car...if I can get the torch in there.

 

[ericher69]

If your going through the trouble to source a "scrap" manifold why not just get a "good" used manifold?

 

[Leejohn]

If it was out of the car I would say go for it. You could set your car on fire. If you try in the car, pull it outside.

 

[tthopskin@yahoo.ca]

you ever change a manifold ...you bust a stud off inside your motor head ..then the fun starts .thats why most do weld

 

[Shield Arc]

I can't say I've ever brazed cast iron before but maybe! I haven't brazed anything in years. But people braze manifolds all the time. I remember when living in California in the early 1970s when they really starting pushing their smog laws, headers came out with 3/8-inch pipe fittings brazed to them so you could connect some kind of smog unit, to be some what in compliance I guess.
I must have posted this 50 times over the years, good thing I saved it so I can just copy & paste.

Cast Iron Repair

First off there are six different types of cast iron so you need to know the type of cast iron you are dealing with. Manifolds and cylinder heads are Gray cast iron. If preheating can be used, the preheat temperature for shielded arc welding (stick) should be held between 500-degrees and 1200-degrees. When oxyacetylene welding you should preheat between 900-degrees and 1200-degrees. You should never let the object being repaired get over 1450-degrees. Maybe think about making a jig. I suggest you take a piece of flat bar and match drill the holes of the manifold, then bolt the manifold to the flat bar, prep the crack for welding. Take a weed burner and preheat the manifold uniformly as possible. Make your repairs, then place the manifold in your kitchen oven at 500-degrees for 24-hours. I would purchase the proper temp sticks from your local welding supply.

Nickel 99 can be cut, drilled, milled, and ground. Ni-55 can be ground. The low nickel rod can't be even ground.



Ni-44 for Tig rod

Certanium 889, (stick)

Crown Alloys 255 (stick)

Lincoln Softweld 55 (stick)

Harris / Welco 65 (stick)

Ni-55 (stick)

 

[tthopskin@yahoo.ca]

if you can weld it easily with a mig it mite be your best ..but keep you ground on the manifold not the stud ether....or if its not really the bad put muffler cement on it ..my son just miged the manifold on my backhoe worked good low heat no worpage to the manifold .but he took it off ..was lucky came off good no broken studs anyways good luck

 

[tthopskin@yahoo.ca]

that is a lot of info ..and to do it right ..but were all in a hurry lol and cut corners and if it rebrakes we blam it on something else lol we all do it but that one

 

[Shield Arc]

I saved this from another site.

I do a lot of cast iron repairs with 100% success so far. Last year, after several months of research, I found information on a couple websites & mostly in an old Lincoln Welding book. The process is called "Cold Welding Cast Iron With MIG". I practiced several weeks on broken cast iron parts & broken/cracked manifolds my bro' gave me to get my technique down pat. It has worked with superb results.

I use MIG, 309/309L .030 wire, 98/2(AR/CO2) @15cfh & generally in the 80A range. You can use any gas with a mix of no more than 5% CO2 (ex:95/5). The 309 wire has a carbon content of .01 & works best. The idea is to keep the temperature cool by running short beads <1" & allowing the joint to cool before continuing. After running the short bead, you can take your glove off & lay your hand on the metal & will feel only warm to the touch. Since your pieces are not large, I would suggest shorter 1/2" beads & allow each weld to cool back to room temp before continuing.

 

[texasjohn]

I'm no welder, nor a mechanic...so, guess I'm allowed to offer an idea, just remember who it comes from.

What about using JB weld...high heat...... it has a high temp rating up to 400 or so degrees...I dunno, maybe manifolds get above that...their FAQ's say not recommended for manifolds.

However, I have had extremely good luck with all their products....and on a manifold I think you are just looking to stop exhaust gases and be able to pass inspection...might be something to try, and if it works, fine. If not, you still have to prepare the surface to weld it.

 

[muddstopper]

best luck I have had welding cast was a wellpump head. It had frozen and split just about all the way around the four corners. What I did was place the pump on top of my barrel wood stove and cranked up the heat, letting the piece sit there until it was the same heat as the stove. I then put on everything I could to protect me from the heat of the stove as I stood over it and welded the piece back together. I did this in steps as I could only stand to be next to the stove for so long. Once the piece was completly welded, I just left it on top of the stove until the next morning. The fire died out, the stove cooled off and the welded piece was fixed. As far as I know, the pump is still working and its been probably 30 years ago.