Working in many engines and you’re bound to run into at least one exhaust manifold bolt before breaking back out of the block. While any monkey with a cheater bar could just throw and hope for the best, a wise precaution mechanic will know that proper disposal now beats drilling rear block. The basic problem
The exhaust manifolds are not only the hottest part of the engine; they and their bolts represent a junction where several hot parts of different composition in contact with the cooler components. Because metals expand and contract with temperature changes, according to their molecular composition, nuts, screws and bolts holding the engine block manifold tend to be paralyzed. Rust – excess oxidation as a result of continuous heat – is another contributing factor, but the heat seizure is usually the primary
Bolts pretreatment
Pretreatment Bolt is the easiest way to facilitate the extraction of multiple bolts, and may be sufficient if the bolts were not taken very badly. Spray all manifold bolts – the heads and cylinders that connect the manifolds to the exhaust pipes – with a generous amount of penetrating oil. Spray along the interface engine manifold and use all you need. Respray manifold bolts two or three times in one hour and allowed to sit overnight if possible.
Works the bolt
Try to remove each screw after giving time to the penetrating oil to work. If the screws to move a little, they work side to side while constantly lubricate bolt threads with oil. If the screw reaches half turn so that back in. The oil in the upper threads of the threaded holes in the block is lubricated, which facilitates extraction. Apply adequate pressure to the stuck screws, but if you will not go, then it’s time for a little heat.
Warming pin
This is a last short shear or screw breakage, but one that often works. The use of an oxyacetylene torch set amid – the flame near the yellow half blue and half – only heat the screw head until it starts to turn red. Ask someone close hold the torch while try to remove the bolt, in case you have to reheat. Do not attempt to use penetrating oil on the hot stud, just going to flash and fire. . Try to work the bolt back and forth.
The Last Resort
If the bolt still does not work out, you have two options: you can cut the bolt head with a grinder and cutting wheel, or to continue applying pressure until the bolt snaps. Of these, the last is the most dangerous because the shear bolt may well flush with the block. At least decapitate pin leaves you with the option to repeat the steps and trying to remove the stem with a pair of vice grips. If you get to this point, try to grind a small flat on one side of the shaft to help get vise purchase.
Prevention
After finally getting the manifold bolts out and remove the persistent lump of cast iron, you may be tempted to say to yourself. “Well, this is the last time I’ll have to do it again” Not so fast, there, Speedy. You will be surprised how quickly can turn manifold gaskets after installation, then you’ll be cursing the new. Even if you think that you never have to remove these collectors more, make the car engine or the new owner a favor and apply some anti-seize compound to the threads of the screws before reinstalling. Anti-seize is cheap insurance, and its use is something to feel smug and after cautious about air.