Since purchasing the Jeep we have had a dreaded heat shield vibration at around 3500 rpm. It's quite annoying and makes you assume something is wrong mechanically. After a trip to Crossbar Ranch in Oklahoma I decided it was time to find the cause. I started with the exhaust header heat shield. That seemed to make sense being attached to the block and subjected to any rpm changes. Upon removal is when all the trouble began.
What We Found
Taking off the heat shield was easy. I lubricated the exhaust manifold bolts that secure the heat shield for a couple days with thread penetrant. Then carefully ratcheted them out by hand. Upon removal of the heat shield is when we found the cracked exhaust manifold. This is a common issue on Jeeps and I really had no issue with having to replace it. If only it was that simple. I decided to soak the bolts every day for a week with thread penetrant to make sure of the best chance of successful removal since they were rusted. It was during one of my daily applications that I found a real problem. Someone in the past had tried to remove one of the bolts and broke it off in the engine block. They didn't bother to repair it. Now it was my problem to deal with.
I continued lubricating through the week in preparation for removal. First task was to get the manifold off to see how problematic the broken bolt was going to be. All of the manifold bolts came out easily by hand. The penetrant had worked its way completely in the threads making for simple extraction. It was obvious whoever broke the one bolt off had no mechanical experience. They just stuck a wrench on it and began turning as hard as they could until the bolt snapped. Instead of repairing it they left the broken bolt in the engine block.
How We Extracted the Bolt
I decided to lubricate the broken bolt for another week. Every day I would go out and apply more thread penetrant to it. This was done to maximize our chance of successful extraction. I ordered a left handed drill bit and bolt extraction kit along with a 90 degree drill handle. The bolt was in the furthest position against the vehicle firewall which made it impossible to get a drill close enough to start a pilot hole. Other than the inconvenient position I had to get in to use the tools the bolt came out quite easily. I drilled a hole in the bolt. Drilled in the extraction bit and the bolt just threaded out without issue.
Repairing the Manifold
After removing the broken bolt we went to Summit Racing and purchased a new Exhaust Manifold. We also purchased a new gasket and mounting bolts. Total cost was right at $100. I couldn't have been happier. I replaced the manifold and repaired an issue we didn't even know about. Along with that we found the vibration as well. It was a heat shield on the exhaust that had a broken weld.
What Happened Next
All of this took place over a 2 week period of time. I was careful to lubricate the bolts well because I know how hard they can be once rusted to remove from an engine block. When we purchased the replacement bolts they came in a set of 12. Six for each side. Yesterday I decided it might be a good idea to go ahead and just replace the manifold bolts on the other side since we had extra. I began lubricating the existing bolts with thread penetrant same as before. That is when I discovered someone had broken a bolt off on the other side as well....