Difficulty Level: 4 Difficulty scale: Adding air to your tires is level one Rebuilding a BMW Motor is level ten
This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
[click to enlarge]
Cracked exhaust manifolds have plagued the E30 and E36 models through the years. The manifolds installed on these cars are made of cast alloy steel. This alloy is heavy and durable, but over the years, it can become increasingly susceptible to cracks. It’s not uncommon to discover a loud exhaust leak coming from the engine compartment. If it’s not a worn-out exhaust gasket, it’s most likely a cracked manifold. A cracked manifold will introduce an exhaust leak into the system. Besides making the engine noisy, it can cause the engine to run roughly and erratically.
The exhaust manifold connects each cylinder’s exhaust ports to the exhaust system. Before you go near the manifold, make sure the car is completely cold. To remove the manifold, you will need to remove the nuts from the exhaust studs on the head. A set of swivel sockets comes in handy, as they are great for reaching nuts in hard-to-reach places. It is highly likely that the exhaust studs will come out of the manifold when you try to remove the nuts. If this happens, replace the studs with new ones, as you cannot properly install the manifold again using the studs if the nuts are frozen on them. You won’t know if the stud bottoms out in the head or if it’s actually holding on the exhaust manifold, and that’s why it’s best to just use new studs and nuts.
On 1996-and-later cars, you have to remove the secondary air check valve and pipe from the exhaust manifold. Also, on some models, you may need to remove the oxygen sensor prior to removing the manifold (see our O2 Sensor Replacement article).
A word of caution: Always use new exhaust gaskets when reinstalling the manifold. If you reuse gaskets, you may introduce an exhaust leak into the system, which can result in a noisy engine and erratic engine performance.
If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.
Figure 1
Here’s a shot of the old exhaust nuts and the rusty studs. I recommend spraying the area with a penetrant prior to removing the studs. With this E36 manifold, a lot of force was required, and the nuts froze to the studs. However, with the right amount of leverage, the studs came loose. In the lower left, you can see new exhaust gaskets, new studs, and new copper nuts. Use antiseize compound on the nuts when you reinstall them (lower right).
Figure 2
When I removed the cylinder head to replace the head gasket on this E36 (see our head gasket replacement article), 100 percent of the exhaust studs came out of their holes in the head. The exhaust nuts had frozen solid on the studs. When attempting to remove just the nut, the stud loosened up in the head. I ordered 24 new studs (yellow arrow) to replace the ones that had been removed—it would have been impossible to remove the nuts without damaging the threads. The inset photo on the left shows the old exhaust studs with the nuts still firmly attached to them. The inset photo on the right shows the swivel sockets that are perfect for getting into these tight spaces.
Get FREE Ground Shipping with the purchase of $75 in qualifying parts
