I've never tried... _{(well, there was that one time... but we won't talk about that)}, but I have seen it done, and know a few people who have/will do it successfully. I say, if it stops the leak in the manifold, then, bravo to you sir!

The problem is heat.

Cast iron has a much lower melt point than steel. Brazing will give better results with cast iron.

Your repair will prolly last for a while, but will likely fail eventually. This is okay for just a patch, but the manifold should be brazed or replaced for a permanent fix.

The heat of the exhaust will cause early failure of the manifold if you use brass rod. I have welded exhaust manifold before. You grind out the crack to get penetration, preheat, weld the crack, let it cool and have the mounting surface machined to a flat surface. I have never had one returned.

Did you burn thru were the crack ends? Or drill it out?

Nah, this was just a 'have a go'
My daughter had bought another manifold from a breakers as hers had big holes in, the replacement had cracks , so I though it was a 'nothing to loose' shot. So I just ground it clean and ran a very quick scaredy cat bead in the vague area of the cracks (Its not easy to weld with your fingers crossed).
Del

Good on ya'

I might have had a helper with a torch heat the general area up to dull red glow to help reduce heat induced stress during cooling. Spreads the stress over a larger area.

We had a horse drawn mower back on the farm in the 50's with steel wheels. One of the spokes broke. The wheels were cast iron. My dad had the welder come out and braze it. It lasted for the life of the mower.

If the old one isn't needed any longer, I'd paint it Candy Apple Red and hang it on the wall.

Drilling them out would have kept the cracks from running farther.

And don't you mean claws crossed?

The exhaust manifold had holes in it, and a used one has cracks in it... What kind of a car does she have? The manifold seems to be a trouble spot.

It isn't a Chevy Cavalier is it?

It's a very old Hyundai accent 1.5, it was my old one and it's been a pretty faithful workhorse. The best thing about it is the drivers seat, prob the most comfortable one I've met with decent adjustment.
I've made my Daught' promise to let me have the seat when it finally gives up the ghost. The seat in my Nissan Micra is awfull...prob designed to fit the average little old lady.
Del

The high carbon content typically makes welding cast iron difficult - not impossible but difficult.

I'll bet that youtube video didn't show the item cracking wide open a few days or weeks later.

Welding it is easy.......keeping it from cracking afterwards is whats hard. And where very specific practices HAVE to be followed before, during and after or the welding stresses induced will render the item junk in a short time.

Cheers, I see.
Fortunately the manfold won't actually fall of if it cracks right round as the bolts will hold it in place.
My Daughter has resolved to buy a new one if it fails. At least fitting a new one will be quick and easy having done the job once.
Del

After welding/brazing of cast iron, is it worth putting it in say a bonfire to heat it up and let it cool slowly afterwards?

I'm only an amateur welder, (mig, gas and stick), and know enough about welding cast iron to take it to a professional instead of trying it myself. But I'd say the bonfire is a bad idea (my opinion)....but because you have no control over the conditions or temprature even though a stay in a furnace for a period after welding for stress relief IS an accepted part of the process. But it doesn't answer the need for a preheat before the procedure.

But if the part has little value, or replacements are cheap and easy to find, why not give it a try using some of the techniques describribed. I'm used to dealing with stuff thats hard to find or impossible to find. That changes the rules of the game.

Let's write 25,000 posts on putting that bath back together!

I take it that nobody suggested welding as a sure method of breaking.

While every container of coated welding rod has a warning label mentioning toxic fumes, the smoke from these high nickle rods is particularly nasty. It's tempting to stick your face in it like an old blind weldor, but this practice sent me to the hospital once. No fun.

Observations suggest a special rod, and pre-heating the iron so that there is less tendency for cracks to form.

It takes a skilled touch to do it properly, not at all like some of the guano produced here.

Weld done for having a go, though!

I had a Mini Minor head brazed many years ago. It worked OK. The problem with cast iron is cracking if the temperature differential between the piece to be welded and the welding temperature is too great. It can be done if the piece is heated up sufficiently first.

As a back yard fix i went for the Pre Heat method and instead of running a Bead of weld i went for "Stirring" as if to "Dilute"? the two Materials and then Peen during initial cooling.This worked very well with Arc and lasted on an old 2 stroke Marine cylinder head.

I realize this forum is about welding cast iron, but for most needs, wouldn't brazing work as well? I had a starter hole busted out on an automobile engine, and a guy brazed it back on. It worked perfectly and lasted as long as I needed it to. (The car rusted away, I didn't sell it)

Cast Iron welding is a bit tricky but not impossible however and a big however depends on the quality of the cast iron. In the case of the manifold if you have an old cyl. head to bolt it to for alignment this would be great to reduce stress after. Preheat the cast iron and weld with a high nickle rod making short passes about 1 inch then peen the weld for a few minutes as it cools to reduce stress. Continue this maybe even moving to opposite side for next short pass but peen every time. Hammer and center punch work well for peening. Keep the heat on and you should have a good weld. If there is a lot of sand or contaminants in the cast life can be hell. I have used the Dillon Welding Torch on cast and does a wonderful job but you need cast rods and special flux. Avoid brazing on exhaust manifold since the heat will weaken it quickly and failure is imminent.. Do not try to weld antique stove parts just full of contaminants and when done looks great but that loud crack as it cools is depressing.

Two of the classic ways to weld cast iron are with a stick welder or bronze welding. In both cases the work must be preheated and the whole casting kept hot during the process..

With the stick welds you should only make thin runs of 1/2 inch or so in length and peen the weld as it loses temperature with a CROSS peen hammer to expand the weld and counteract it's shrinkage. It can be a slow process but, if done well, a completely satisfactory joint will result.

When bronze welding cast iron you should file the surface to be welded after a vee has been formed with a grinding disc. If the surface has been filed and the correct flux used, an excellent joint can be achieved.

Your welding supplier will advise on what rods and what flux to use. The casting must be allowed to cool evenly and slowly after welding.

SRIDHAR, I give you a GA for your concise and very informative posting.

I learned something new today about welding ad brazing all types of iron!

It is a pleasure to share my experience with others and a big thanks to you guru.

regards, sridhar.

I have to agree with CaptMoosie and a GA from me too. A well thought out reply that is well put

Thanks for all the great input guys.
Next time I have to weld a casting I'll have a better idea how to proceed.
I don't have much in the way of metalworking kit, just a cheapo arc welder. I do have a propane torch and next time I'll at least try to warm it up a bit before having a go, or maybe I'll see if I can get some brazing kit.
The last bow I made broke , I wonder if you can weld Hornbeam.

Del
_{(The bow I'm working on currently is coming along fine tho')}

See what you've done!

You've got all these people in a tizzy over the proper way to do something you've already done.

I suppose it's not your fault that you didn't know it was so complicated, and just went on and did it.

It's kinda like my parking garage. Everyone is so intent on telling you what you should have done to prevent failure, nobody cares that you've already got the bloody job done, without any problems and without any advice from the "experts".

I, for one, am glad to see that you had a go at it.

It's tricky, but we do it all the time with NI-CL sticks. This little calculator comes in handy when deciding pos/neg config as well as amperage settings.

http://www.millerwelds.com/resources/calculators/stick_amperage_calculator.php

Here is a link to the Muggy Weld website I mentioned.Lots of good info on welding cast iron.

http://www.muggyweld.com/castiron.html

welding cast involves preheating the cast iron until it glows yellow "the whole piece, not just the area to be welded". you must keep the temerature at or near yellow as you weld it. that usually requires reheating every few minutes. stitch weld a few inches at a time and at intervals starting at the ends of the crack towards the center to prevent stresses. if you have'nt destroyed it during the welding process, reheat to yellow again and very slowly allow the temperature to drop to room temperate. it should take 6-12 hours of slow and even cooling in order to relieve the stesses of the welding process.

many expert welders won't even try.

I have welded 100's of cast iron parts, this application dose not used bronze or nickel rod. It is done with a torch and cast iron rod. When competed you will have to face the mouting surface.

(semper) multi modi variique quis/quibus felis decutiatur.

(Apologies to Del)

Showing my ignorance a bit but what is "decutiatur"? My latin dictionary did not have it....

There is a cast iron rod that can be used.the trick is to pre heat the piece also I have had good results

gas welding using a brazing rod.

oilcan13