Safety Alert Ford Sierra Compression strut problems

[marlinmick]

Re: Safety Alert Ford Sierra Compression strut problems

To me the problem looks like Embrittlement Fracture around the periphery of the weld caused by the Heat Affected Zone (HAZ) in the Parent Material from the welding process as the fracture is not in the weld or mounting block itself.
The parent material molecular structure changes at the extremities of the weld site hence HAZ so any stress induced flexing would cause the metal to fractures at the HAZ site.

The simplest solution to me would be to remove the original mounting block by grinding the welds off and manufacturing a new larger mounting block and welding it onto a larger spreader plate to distribute the load over a wider area and then weld it into place on the chassis that is after first giving the whole area a good clean back to bare metal and checking it for soundness. It would do no good to re-weld over the fracture site as although this would re-fix the mounting it would not cure the HAZ problem.
I'll have a look at my Cab to see if mine has the same problem.

[andyf]

Re: Safety Alert Ford Sierra Compression strut problems

As this problem to the best of our knowledge is confined either to those Cabrio's fitted with the BMW engine and consequently a 'chopped' anti roll bar , or those vehicles that have been modified from the original design and have a compression strut set-up, I would suggest that it's more likely a result of entirely different stresses being imposed on that area.
There are a number of Cabrio's out there with the standard set up and greater mileages that have not had the problem.
Unless you could cut a section from the mounting plate and incorporate the chassis rail and welds, and then put it under the microscope you cannot categorically say that the failure is due to corrosion or whether the corrosion is a result of failure.
Marlin got it wrong in respect of chopping the anti roll bar to fit the M20B25 engine and a number of owners by installing what they thought was an improvement .
I was one of those members who had the BMW powerplant in my previous Cabrio

I think you've hit the nail on the head. If the mount was designed for an anti-roll bar a lot of the twisting moment on the mount would have been taken up by the anti-roll bar, when the bar running across the car was removed so was some of the strength. That would suggest that the mount should be reinforced to cope.