22 replies to this topic

[Spitz]

About three years ago I welded in a new floor panel.
About two years ago I switched to solid mounts at the rear of front sub frame.
Found this today!
What is the fix? Weld a steel plate across the cracks? ( after I weld them up that is )

[minidaves]

take the mount out and see what it looks like

[dave-88_123]

isnt there normally a spreder plate welded in there

[dklawson]

Spitz, though I have not personally experienced that failure (yet) I do remember it being discussed a lot (on the MM board) when I was restoring my Mini. Apparently it is not that uncommon and I do remember several people suggesting exactly the repair method you describe.

You've got me nervous now.... I am afraid to lift the carpets up in my car.

[Spitz]

The mount is absolutely fine....

I think I will just reshape it....weld up the cracks...then weld in a 1/8" or similar plate across the area ( maybe not that thick )
I need to soon replace the floor on the otherside. I'll do the same to that side before it cracks ( still factory on the other side )

[bmcecosse]

You need to check the other subby mounts - it must have been able to move/squirm to cause that cracking,,,,,,

[Tupers]

I've big 1.6MM plates to the floor of my estate to give the toe board mounts some reinforcement.

Edited by Tupers, 23 July 2012 - 08:59 PM.

[Cooperman]

Drill a small hole, say about 3/16" dia, at the end of each crack, then weld up the cracks and grind back both sides.
Fit a good size doubler plate made from 16 swg (1.5 mm) steel sheet and both seam and plug-weld it in place. Grind back the welds, re-drill the holes and 'jobsagoodun'.

[Spitz]

Went in for a closer look...did some wire brushing.
The cracked portion is the new floor plate put in a couple years ago....but....it overlaps that much over the original floor.
The original part is still fine ( original metal ends just below the lower bolt hole )
From the outside the orignal metal is fine.
What I think happened is I didn't press the two together well....and hammer them together.
I'll weld up the cracks and make sure I weld the new floor layers together....I'll then ad a plate.
I'll see what sheeting I have on hand.

[tiger99]

Spitz,

Why is the new floor overlapping the old? That is a serious rust trap, amongst other things. The old panel should have been removed, and the new panel seam welded in. Otherwise, you will have never-ending problems.

There is an overlap between floor panel and lower bulkhead panel, which should be spot or plug welded in both the horizontal and sloping parts, but the mount bolts do not pass through that.

Also, your mounting bolts seem to be incorrect. There is usually a metal strap with two captive bolts fitted. That is probably not the cause of the problem, but the proper fixing does lie flatter under the carpet, and makes it easy to change mounts, because you only need to tigten up from underneath without a spanner on the other side.

bmcecosse,

I agree, something has been moving. Likely the inner wings are cracking just ahead of the subframe towers, or possibly the top bolts are bottoming against the subframe before clamping tightly on the crossmember. Some washers should fix that. Otherwise, the cracking is a typical symptom of what happens when solid and rubber or poly mounts are mixed, which seems not to be the case here. I assume the front end is steel, not GRP?


Generally, the mods outlined by Cooperman or Tupers should fix this permanently.

[podifold]

On mine I seam and plug welded in a 1.6mm plate covering the entire mount area and also made up some new mounting brackets with a larger foot and 4 bolts instead of 2 to spread the load.

[Spitz]

The floor overlaps....just because thats the way I did it.
The overlap area was filled with seam sealer.....never a drop of water got in.
Yes...metal front end.
Thanks for all the advice.
I know erros were made...the biggest being the area of overlap....which I will plug weld today and put reinforcement plate in.
Minipickup....I may copy your idea with the mounts. by the way....that hinge looks familiar...is this jon from minipickup dot org?

[podifold]

Yeah, that's me.

I'm gonna be making some of those heavy duty solid floor mounts to sell in the near future.

[tiger99]

minipick-up,

Your design will serve admirably to reduce the risk of subframe intrusion in an accident, a known weakness in the Mini. I think it was not so bad when the rubber mounts were introduced, because the rubber mounts, if they had not already fractured, would seperate in the accident and allow the end of the subframe to bend down and slide under the floor, but on early models it was very common for the area to cave in completely, because the impact was transferred straight through the subframe into the floor.

At the expense of weight, you could improve it further by running it all the way to the wheel arches.

I do like your mounts. Not difficult to make, but very nicely finished.

[Spitz]

Fixed !

Next thing is to replace the left side floor. Without the carpet in, I can see the road go by while I'm driving