Volvo d12 exhaust manifold leaking

Well,assuming the exhaust manifold is not cracked and you are using new bolts? If you re using Fel Pro gaskets that dont use sealer? They have one side"that says towards engine etc.They have to be installed (oriented) with the correct side or will leak.My trick is this: I dont use the fel pros.I use another quality gasket instead,being thrifty.First every bit of the old gasket off (all of it) and get some 3M weatherstrip adhesive and get a moderate even coat smeared on the engine side of the gasket.This stuff is great and holds the gasket in place perfectly.Press gasket down tight and even.Use some New bolts and tigten down criss cross style ,little at a time.Torque wrench is your friend Tighten to ft lbs specs.Let truck sit for a few hours.Start it up,idle for 30 minutes. Shouldnt leak .

 

Where is it leaking at? At the head or around where they join to one another? Why buy a used one?

 

there is a special paste that volvo offers to seal small leaks when it heats up. i have had good luck with that its possible that the manifold is not flat if the old gasket sliped on one side then the manifold is prob ####ed. the only thing i can advise is that make sure you are putting the gasket on the right way. it will tell you which way is manifold side and use new bolts tight in cross pattern. i'm pretty sure you did everything so just make sure the manifold is flat.

 

its always worth it and i always do it i never put a manifold back with same bolts always new and probably need to replace the manifold for a good one as well if gasket slipped its going to keep doing it until it's perfect flat surface

 

I have a 05 d12d and want to put a d12c on it to be rid of the twins that are not working. And just adding space. My exhaust brake blew out the slip joint seals so I am losing boost and can hear it whistle. I know I need new bolts when this job is done along with manifold gaskets question would be can you mix manifold parts? Or could you brazen the slip joints closed?

 

I am getting a whistle at 65 mph exactly,computer shows 7.4mpg and i measured full to full 5.4mpg
Could this cause it?