Exhaust manifold repair on DD Series 60

Hey guys I'm new to the forum but have been trucking for the last 32 years. Over the past while I have gotten some real good advice and learned a few things from different post's that have been on here. Up until now I haven't had any questions of my own but the other day I saw something that really bothered me. I discovered a crack in the center piece of my exhaust manifold (14L series 60). We're really busy where I'm working and they told me to bring the truck into there shop and they would have a mechanic fix it right away. I would just have to pick up the parts, which I did. I gave them all the gaskets and the new center piece. When I returned from the dispatch office and went into the garage to see how things where going I was shocked to see the mechanic hitting one of the end pieces with a sledge hammer. He was trying to seat it in the new middle section that he had clamped in his vice with no softeners. I stopped him and asked him what he was doing, why is that manifold in a vise and why are you hitting that piece with a hammer. He said that's the way he has always repaired them. There is now a groove straight across the machined side of the manifold from the vise. I was pissed and told him to stop working on my truck. The shop manager (the mechanics father) says they will use liquid gasket and everything will be alright. I don't think so and my truck is still not fixed. Am I wrong, I thought you would mount the center piece on the engine then put the ends on but I'm not a mechanic. As well I don't feel good about him hitting the end with a sledge hammer. Good if your trying to break it not so much if you trying to fix it IMHO. Should I go to the owner or are they right?

 

It's not just the damaged piece that I'm worried about. I think the way they where trying to fix it was wrong and wander what kind of damage was done to the end pieces when they where taking the manifold apart. Is it ok to hit the manifold with a sledge hammer? It's cast and 12 years old, I'm worried about cracks that I can't see. Or is this the way all shops fix exhaust manifolds?

 

That was my thoughts. I saw him hitting it hard with the hammer when he was trying to put it together. I can just imagine how hard he was hitting it when he was taking it apart. What confused me was that the other mechanics in the shop didn't think it was a big deal. That's why I thought I'd put it on here to see what others would say. I just got off the phone with the parts guy at Freightliner and ordered a whole new manifold. Thanks for your replies.