Last Updated 19 December 1999
This is a serious problem, and rumor has it that several cars are currently off the road because of it. At present, Vauxhall are unable to supply any new bell housings. Apparently, Frosts (one of the LC approved dealers) have had one on order for a customer since November 1998. The story goes that Lotus shipped 300 bell housings and clutch sets to Vauxhall some years ago. This consignment has been lost. In the meantime, Lotus have lost the mould for the bell housing, and so can't make any more. A little birdie says that they are in the process of making a new mould, so they should become available again - eventually. In the mean time, if this problem hits you, your only option is to try and patch it up.<UPDATE 19-12-1999> Bell housings are now available for £423 + vat. Thanks to Simon Reynolds for that info
There are 2 designs for the bell housing - The original part was 90393286, and was fitted to cars 0001 to 0777. A revised bell housing 90393830 was produced incorporating changes required when the clutch release fork pivot design was changed. Cars 0778 to 0950 were fitted with this design. Any early car that has had any clutch problems in the past will probably have been retro-fitted with the new designs of bell housing, release arm and release pivot. It doesn't matter which design you have on your car, both are prone to the stress fracture problem
The clutch bell housing is a large aluminum casting (1) that surrounds the flywheel, clutch (5) and clutch pressure plate (6). It is bolted to the back of the engine, and then has the gearbox bolted onto it. Also mounted onto the bell housing is the clutch activating mechanism.
Click on the image for a larger view (216KB) Firstly, there is a hydraulic piston (15). This pushes on the clutch release fork (8) which pivots on the clutch release fork pivot (9), which in-turn pulls on the clutch release baring (6) to activate the clutch. The problem occurs where the pivot (8) passes through the bell housing, and is secured in position by the securing pin (12). There must be tremendous forces at work because the aluminum around the hole can start to break up, as shown in the photo below.
Click on the image for a larger view (241KB). The fracture can clearly be seen running from top to bottom of the large hole in the center of the image. You can also see the edge of the alloy plug repair that I had done, together with the three rivets holding the plug in place. Below is another photo showing the damage and repair from inside the bell housing.
Click on the image for a larger view (265KB). Again, the fracture can clearly be seen near the pivot hole. You can also see the evidence of an earlier attempt at repairing the bell housing by welding. I wouldn't do this again, because welding aluminum is extremely difficult to do, and is just as likely to introduce more problems by making the aluminum brittle. Instead, get an engineering company to cut away as much of the affected area as they dare, and get a 'plug' made up to replace it. Make the plug out of something very-very hard, like aircraft grade alloy, or even plate steel. The hole for the pivot pin has to be in exactly the right place, and the right depth. Even more important is the fit. The pivot must be very snug in the hole. If it's too tight you won't be able to re-assemble it properly. If its too loose the pivot will move in the hole, causing the retaining pin to break off. You have been warned ! Below is a closer view of the repair I have had done.
Click on the image for a larger view (272KB). You can see that my repair consists of a square plug, which is about 1.5 inches square, and it is held in place by 3 rivets. The plug itself goes all the way through the housing, whilst the flanges where the rivets are go about 1/4 of the way through. Just above ant to the right of the plug you can see more evidence of the original attempt at a weld repair. The eagle eyed amongst you may have noticed in the second photo that I have had the hole for the pivot pin tapped. This is because I have also had a new, larger pivot pin made to address another (related) Lotus Carlton clutch problem, namely the pivot retaining pin shearing off