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MG MGF Technical - Front crumple zone and its limits

In the process of repairing the damage from a front impact of indeterminate force, and finding that the bumper box section has flattened slightly across the whole width, and the 'legs' attaching it to the chassis have deformed as presumably they're designed to do, leaving the box section now about 2-3cm from the mounting to the chassis. One lower bolt is now inaccessible until I cut the box section off but there was enough room to get a spanner to the rest. The car drives perfectly, and there is minimal other damage visible, so can I be confident that the crumple zone has done exactly what it says on the tin, or is more investigation necessary?

The bumper cover is almost undamaged, but was left long enough for the 'memory' shape to have suffered. Is there an old wive's remedy to this, something to do with heating & cooling while chanting spells..?

Mike Hankin

I would think you should at least put it on a jig, and measure the chassis plus subframes.

Just to be on the safe side.

Johan Slagter

Mike, I think that I'd agree with Johan: putting the car onto a Jig is going to be the best (and perhaps only?) way to be 100% confident that the front of the car is true.

However, if there is absolutely no evidence of panel creases, and all the damage appears contained to the area of the 'disposable' bumper bar and brackets, then I'd be fairly confident that the damage was well contained to that obvious area of crush.

One check you could perform if you don't want to use a Jig is to measure the chassis datum points (they're indicated in the workshop manual IIRC). This will provide evidence on whether the subframes remain square and within tolerance.
Rob Bell

Thanks Johan & Rob, after another close inspection I still can only find evidence of minimal forces having come past the bumper section. The radiator is untouched and the bonnet slam panel has twisted only slightly, albeit enough to snap the lower clips on the headlamp units on both sides, which is annoying - have bought one from a breakers but am inclined on the other one to see if I can fabricate something that will do the job.

I guess assuming that any further travel of energy into the chassis or subframe would shake things up enough to be showing itself in the steering geometry is a bit too unscientific. Any clues as to what sort of cost I could expect for a jig assessment..?

When this is done, there's the petrol smell, horribly noisy cooling fan, siezed blower control unit, grumbling & lethargic electric windows, soggy servo linkage, smell of coolant, leaking roof and some extensive interior retrimming & sealing - there's even condensation on the inside of the oil temp gauge & clock. Should be finished in time for summer, please do not ask which one tho!

Mike Hankin

Mike, any good body shop should be able to quote. Alternatively, the MGF Centre has a body jig, so perhaps drop them a line to see what advice they can provide.

Looks as though you've got quite a project on your hands there Mike! :o) Good luck!
Rob Bell

This thread was discussed between 06/12/2004 and 08/12/2004

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