Chevrolet Repair: GM 4.3 exhaust manifold removal, pipe flange, exhaust gasket

Question
Hello ,

Vehicle:    1991 Cherolet S-10 Blazer 4.3 liter engine, 2 wheel drive,  
                auto, no A/C.
Problem:   I have a major exhaust leak on the passenger side at gasket
                and flange area where Y pipe meets exhaust manifold.
                Appears that exhaust gasket and a new split type flange need
                to be installed. I've applied a sealant around this area to help
                quiet things down as a temporary measure.

Question:  Is it advisable to remove exhaust manifold from engine to
                help facilitate easier repair (it likely will need new studs for
                the Y pipe flange), or try to do this with manifold still
                attached? My main concern is to AVOID snapping off the  
                manifold bolts where they join to the cylinder head. They
                look relatively solid, but that is only a visual check. Should
                they be heated up with a torch, (how much?)
                or can they be removed as they are. I almost expect studs at
                Y pipe area to snap off, but if manifold bolts aren't a risky
                item to remove I can always drill out the Y pipe studs a whole
                lot easier with the manifold in a vise on my workbench. I am
                worried about snapping off a manifold bolt in the cylinder
                head and then having a real mess on my hands.Please advise.

Thank you,

Rick  M.


Answer
Hi Rick,

Exhaust work is cheap but nerve racking.  I tend to sublet this work on the cars I do, at least at the manifolds.  

I would call the corner muffler shop and ask them how much to drill out the bolts.  Tell them you broke them already.  Don't call the big 'chains', but the corner guy.  Many times they will drill these out for $10 to $40.  That is cheaper and easier than pulling the manifolds.  New gaskets will cost at least $15.  How much is your time worth.  If you like the price, then go for it.  If you break the bolts, then you know what it will cost.  Just drive the car to the corner guy.  It will be loud.  

If you do break these bolts and don't want to pull the manifolds, they make a split ring now.  This plugs together around the manifold collar.  Run new bolts to a collar on the new Y-pipe.  This doesn't work on every manifold.  

If you decide to pull the manifold, you can heat the bolts cherry red.  Don't direct the heat at the head.  Stay on the bolt.  When you pull these bolts, you may get one or two that leak anti-freeze.  Remember to put sealant on these threads before you put the bolt back in.  Remember to torque the bolts or you may warp the manifold and get that annoying exhaust tick.  You are supposed to have the manifolds resurfaced, before you reinstall.  Remember to clean the threads on the bolts, prior to reinstall.  

Manifolds are not all that risky.  Heat helps.  Go slowly, quarter turns.  They are only 35 foot pounds, or so, tight.  

I hope this helps.

C J S