Manifold bolts are rusted tight


How would I remove the bolts holding my exhaust manifold on off if they are seized to the head? I have a cracked manifold and I need to remove it but the bolts just wont budge, (also accidentally I busted two of them off trying to loosen them.) The only tools I have are basic ratchets and a 3/8 breaker bar and a portable torch.

Also, what would be the best way to remove the busted bolts that is inside the head?


Lots of PB’laster. I don’t use WD-40 for this. PB’laster is a great penetrating lubricant that will help loosen the rusty bolts. But, you’ll probably need to use a few applications to get enough in there to work.

As far as the broken bolts, the best method is to drill out the bolts and threads, and install a heli-coil. I also like to convert to studs, since they are easier to work with.


how much of the bolts is left, outside the head, or inside the head? usually when you get all the bolts off and remove the manifold they are sticking out above the head.

hopefully there is enough left to get a high quality wrench on to remove the rest. REMEMBER… HIGH quality wrench. not a cheapo. people get cheap chinese wrenches, channel locks, vise grips and pipe wrenches that have inferior fit, finish and tolerance. the cheap tools will strip round off and tear up more work than you could imagine.

PBlaster is GREAT use it copiously. then use more.


Agree with the previous posts, but for removing the busted bolts, Craftsman has a bolt removal tool that works fairly well if you have enough room.


Plan for the possibility you will not be able to get the busted off pieces that are stuck in the head out with the tools,skills you have.And the head must come off and go to the shop. Just trying to keep it real for you.Rusted,busted stud removal is just a hair short of an art.


Thank you all for helping me.
I was wondering also if it would help at all to heat the manifold with a torch to get them loose.


To remove the remaining bolts, take the torch and heat the heads of the bolts until red hot. Then let them cool back down. This will cause the heat to move down the bolts into the threaded sections causing them to expand slightly. Then as they cool down they’ll shrink slightly and break the bond at the threads.

For the broken bolts, the best way I found to remove these is with a MIG welder. Place a flat washer centered over the broken fastener and weld through the center of the washer to the broken fastener. Now take a hex nut and center it over the washer that was just welded on, and weld through the center of the nut to the washer. Again, doing this heats up the fastener down to the threads to break the bond as it cools. And you end up with a new hex head on the broken fastener so it can be turned out.



Tester strikes again !

BTW ~ the bolts usually sieze to the manifold flange rather than the threads siezing in the head. Provided you can get the manifold off, removing the broken bolts should be easy enough with a good quality (ie not Chinese) self grip wrench. The exception is where the exhaust manifold bolts actually screw into the head coolant waterway and have corroded due to lack of colant corrosion inhibitor, though the majority of these use studs. You don’t state the make, model but some exhaust manifold bolts need thread sealant to prevent a water leak through the head thread, you might want to check this isn’t the case with your heads.


Serious heat will break the bolts loose. A propane torch is seldom enough. You will need an Oxy-Acetylene rig to bring the bolts up to red heat. After THAT treatment, they will turn out with little effort…Also, before you try to loosen them, try to TIGHTEN them a little, THEN loosen them…

When heating the bolts, be careful not to overdo it and melt them.


Worse case scenario was replacing the exhaust manifold on 66 Caddy with a 429. I had to get a power chisel and break the manifold off. Then I had the bolts exposed sprayed liberal amounts of liquid wrench (PB Blaster wasn’t invented yet). Let it sit over night…then get a couple of vicegrips and remove them. It was a real pain, but it worked. The problem I was having was getting the liquid wrench into the bolt threads. I could only spray where the bolt heads were which was about 2" away from the threads. It was better for me to get the manifold out of the way…and since I was replacing it anyways I just broke up it apart.


If you are working on a Ford big block you may find the head breaking at the lower manifold mounting bosses.