The exhaust manifold on the TC models is well known for being prone to cracking. This simple modification will help to alleviate the problem as much as possible.
The TC exhaust manifold is a rigid mild steel tubular construction that is often quite badly made. We know of some that don’t even fit flush to the cylinder head face and require extra gasket rings on the exhaust ports to create a seal. Likewise the front exhaust section, to which the manifold joins, is also often poorly made with most systems in use now being reproductions of some sort. So the chances of the manifold being in the exact location to mate with the exhaust front section are pretty low. Because both pipes are rigidly held in position, then unless the exhaust front section and the manifold line up nicely, stress will be placed on the manifold from engine vibration and this encourages the development of the fractures.
The simplest way to help cure this problem is to completely remove the front exhaust mounting on the bell housing next to the starter motor. This front mount is not actually required because there is another support further back on the gearbox. The front mounting removes any scope for “adjustment” at the joint and with it fitted, can require some forceful persuasion to insert the pipe into the manifold. Both pipes are then constantly under stress.
After removing the front mount, undo the gearbox mounting completely and then slacken off the joint between the front and mid-pipe section, breaking the exhaust sealant so that the pipe has room to move. Use the free movement on the rear olive (only a few degrees) to align the front pipe and the manifold. With the pipes now aligned, you will probably find that the gearbox mounting hole is now in the wrong place and you will need to file a bigger hole to make it fit. Apply exhaust sealant to both flanges and tighten each end gradually and alternately, otherwise the tightening process will pull the pipe straight and back out of alignment. Finally tighten the gearbox mounting using a large washer to cover the enlarged hole, and leave the front bell housing/starter motor mounting removed from the car.
This should leave your exhaust manifold free of excessive stress and likely to have a much longer life. At your next MOT it is quite possible that you will receive advisories stating that the mounting is missing, but it is not a failure point, they are just required to tell you on the advice form.
Words: Brian Humphreys
Originally published in Driving Force magazine
August 2013