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Discussion Starter #1
Hi guys,

My exhuast manifold has a hairline crack on it. I can feel a lsight leak when the engine has just been started.

Is it possible to weld this crack? It is not a gaping crack just a hairline crack.

If it could not be welded does anyone know how much a replacement manifold would be (New or used) in £s and where I could source one in the UK.

Cheers
 

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They can be welded (I've had 2 done), but you really need to get it done by someone who knows what they are doing as cast iron is nowhere near as simple to weld as steel.

As for replacemnt - new I'd guess about £150-250, used anything from a fiver :)
 

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Just looked into this myself a few days ago. Basically what nutcase said - it can be done, but its not a MIG job. Apparently, cast iron expands and contracts so much that the welds will simply drop off. The manifold itself needs to be heated red hot and then the crack properly gas welded. I was advised that it was questionably worth it, as even when done properly a welded manifold won't be as reliable as a S/H one...
 

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Discussion Starter #4
Hi thanks for the response guys.

Does anyone know if this is a common problem with the SAAB 900?

Cheers
 

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Welding manifold

I think there more like £3-400 new, you should be able to find a good s/h unit for about £100. I've just welded up some cracks on mine, dunno how long it will last though, hopefully a few months or so until i can source a good s/h unit.

The T8 manifolds are prone to cracking and i think it's a pretty common problem.

I had mine done previously by a proffesional welder for about £40 and those welds are holding up fine, I've got a spare one with cracks so i may get than done aswell.
 

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I had my exhaust manifold welded up about 18 months ago, with new exhaust gaskets, replace the broken studs it cost a grand to of £80 but only £25 was for the welding...

I think it needs welding again :roll: :roll: different new small cracks again

Paul


______________________________________
Full Throttle until you see God, then Brake....
 

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i have heard of people fixing exhaust leaks like that with clay mixed with some ash and salt to make it stronger. The clay is burned becouse of the heat and becomes rock hard. Put the clay around the crack and strap a coupler or something around it, drive until the clay is rock like.
Havent tried it myself though.
Doesnt cost mutch so it would be worth a try ;)
 

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you can get cast welding rods for an arc welder, not sure if it needs heating first, but if so give engine a good run on revs, soon get hot and arc away. i have 16v turbo so does a friend and both have a flaw(lookes cracked) between 2-3 cylinders.but no leaks. have a standard 16v exhaust manifold cheap as well.
 

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I found it!

I have been looking for this since the thread started:

somewebsitedealingwithcastironstoves said:
Jan 22, 2004


I recently repaired a cracked cast iron mantel. Welding is very tricky with such a large piece so I glued the two pieces using a high heat bonder/putty called Pyro Putty (2400). It worked very well!

Name deleted by Marcos
- Victory Mills, NY, USA
Sourcing: Pyro Putty 2400 from Caswell Inc.
I figure that if it works for a stove, It'll work for the manifold.

NOTE: I have never, ever, in my wildest dreams done anything like this. Well, maybe once, but it was a wild dream, and I have no idea if this will work. I did try welding cast iron, and I can tell you it's a biatch and a half to get right, and the good weld does not look any different than the bad one.
 

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Not sure what a roaring stove will get to on temp - I've seen them on a dull orange glow so pretty hot. A turbo exhuast manifold will get a fair bit higher than that though, with a lot more gas velocity and probably more thermal shock. Might be worth a try with the putty, but don't hold your breath :)
 

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Agreed, it may not work... but for the money I feel it's worth a shot before undertaking cast iron welding. For one it won't require a buddy holding a torch to the part to keep it red hot :)

Again, it's just an alternative fix to try.
 

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You beat me to it!

I actually went to the parking lot and opened the hood to check it out. I listed it because the seller called it an "early 90s" and, at least in my head, that means the classic 900, rather than the NGs.
 

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Some more info on cast iron welding

http://www.lincolnelectric.com/knowledge/articles/content/castironpreheat.asp

This is right on point:

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

and some tips from someone who's been there:

John_in_MA said:
The basic trick is to use 99% nickel rod in an AC arc welder. Deeply bevel the edges. Build it up bead by bead. As soon as you lay a short bead, peen the glowing bead with a hammer and keep peening for a little bit. That'll help even out the stresses. Then clean carefully and repeat. I've done this with great results (even with a cheap 110V welder) on very thin parts. No cracks so far.


Preheating makes it safer, but it's not required if you're careful. It's more of an issue with torch welding. Or you could brass braze it, although it's not as strong or pretty.
and someone who tried (to weld cast iron, not manifolds)

Me! said:
Heat your kitchen oven to about 500 F and put the piece in it after you're done welding it, shut the oven and go to sleep. Don't open the oven, though, or it will cool too fast.

you can do the hammering with a regular welder's hammer, and it lets you see where you're hitting because it leaves small peck marks. Keep hammering even though you think it's cold.

Most recommend 99% nickel rods, I don't see a difference in the results compared to the 55% nickel rods... only 55%ers are way cheaper.
I use a cheap buzzbox I got at Harbor Freight for under $100. A whole $1 under $100! :)
 
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