REPAIR HELP PLEASE!!!

Ok so... I'm a very experienced welder myself. Yes, cast iron can be welded reliably... If done properly. I have welded many cast gear boxes, several other small cast parts, and ONE exhaust manifold. Never had a cast weld fail, EXCEPT the exhaust manifold... I did it 3 seperate times, on the same manifold. Each time it eventually cracked again.

My advise? Replace it with new.

 

Cattleman is correct, welds on exhaust manifold is tough but, we used to use stainless 308 rods and a particular way to repair . You can’t get in a hurry fooling with cast . Now patco has rods especially for cast however, 5 lbs will cost as much as a good used one.

 

that seems to be alot of guys' maintenance programs

 

Correct. It has to be welded at the correct temperature. You have to heat up the cast iron first to a certain temperature before you can weld it, then you have to be a #### good welder to weld it. And have to know exactly what you are doing. You'll either blow through the cast iron, or it won't meld to the cast iron, or there'll be pin holes in the hole which will leave impurities in the weld otherwise causing a less than ideal weld which will cause problems. Especially it being a turbo and it coming from the exhaust. If not done exactly perfect, you're gonna lose the efficiency of the turbo, lose mpg's, and it's gonna throw all kinds of emission codes most likely due to exhaust leak.

 

There is a certain Rod that you use to weld cast iron but honestly for what it would take to find someone that can do that that knows how to do it that has the right rods for it...

And as others have said where that repair has to be done it's not likely that it will hold up.

Just buy a used manifold and you'll be way ahead.

 

Yeah, you gotta use nickel rods because it's a ferrous metal that has a high carbon content. Which leads to the heat-affected zone adjacent to the weld hard and brittle. Anything cast iron, I just replace. Yes, a #### good welder that charges $200/hr, their weld will hold up, but it's only a matter of time before an exhaust manifold weld will fail again. My guess is due to it constantly being hot. Because to weld it, you have to heat it up, then slowly bring down the temperature with either sand or thermal wrap or whatever before you weld it. And with an exhaust manifold on a semi, you're having temps of 400+ degrees 12+ hours a day sometimes.

 

Yeah, these rates are crazy right now. Have you tried finding the manifold online, and just replacing it yourself? Just get some pb blaster or some kind catalyst penetrating fluid, and see if someone can let you borrow an oxy-acetylene torch to get the exhaust manifold bolts off. You'll also need a 3/4" impact gun to get those bolts off. I highly doubt a half inch would do it. You may get away with it. It may have enough back-off torque on it. A 3/4" impact with a 3" anvil would do just the trick. You could get away without the anvil too if you can't get the 3" anvil. You may not even need the torch with the long anvil.

 

WTF?! A 3/4 inch impact to take out exhaust manifold bolts? Guaranteed to take them out or break them.

 

I've had hell getting them off before with a 1/2" because of the heat and being rusted on. It pretty much welds them on. And that's working on regular 4-wheelers that are 10mm. The one's on semi's are more times than not 18mm. So it's best to use a 3/4" impact that has more striking force. It has roughly around the same torque, but it has more striking force because of the motor. A 3/4" impact gun is more suited for working on semi's than a 1/2". Most of the bolts and nuts are torqued down to at least 140-150 ft-lbs. Some even higher.