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Having owned several different models of Porsche over the years, I know that sooner or later it will probably become necessary to remove some part of the exhaust. Despite the fact the Porsche use good quality exhaust components, the nuts, bolts and studs eventually corrode. As the car ages, it will become progressively harder to remove these parts from the car. The exhaust manifold bolts or studs are especially difficult because they corrode into the cylinder heads, and if they shear off during removal then they will have to be drilled out. This is not something I want to be doing.

Looking at the state of the bolts on my current car, I can see that they are corroding. My car is currently 7 years old.

Although the manifold pipes themselves look corroded, this is common with lower grade stainless steel used in exhausts, and does not mean that the manifold itself needs to be replaced.

Here is a close up of one head:

I decided to attempt to replace the bolts. Having read horror stories of failed attempts to remove them, I reasoned that it is important to carefully pick the best method of extraction. The star fitting of the bold heads look like they will take a good level of force. I selected a powerful impact driver, the Bosch GDS 18v HT. This tool can apply up to 625Nm of torque. What this tool can do is apply a series of sharp blows to the bolt. Either the bolt will come out cleanly or shear.

With a couple of short extension bars on, it fits comfortably under the car:

I started with the most corroded bolt, and tried to ensure the socket was squarely on the bolt. After about 3 blows, the bolt came free. It looked like this:

The bolts are M8, and clearly made of steel.

I decided to replace with titanium studs with stainless washers and nuts. I chose titanium studs over stainless steel for its strength. Whilst there are a number of local sources of these parts, I experimented with several different titanium suppliers and settled on this stud:

I chose 35mm long studs which is slightly longer than necessary but leaves plenty of stud exposed if in the future there are problems removing it.

Stainless M8 flanged nuts like the one shown are readily available and not expensive. I added a couple of washers before installation: