Front Subframe Repair

subframe 1

The finished product, with a coat of POR-15.

I once read that there are two kinds of '02s, those that have had their front subframe's repaired, and those that need it soon. In actuality, it is not the subframe that needs repair, but the bracket that supports the left-side of the motor. This bracket not only helps to hold up the engine, but keeps it from tipping over during cornering. A combination of poor design and severe loads causes the bracket to develop cracks, which can eventually lead to failure.

These cracks are difficult, but not impossible, to detect with the engine in the car. In fact, I didn't even realize that I had them for sure until the subframe had been stripped and blasted.

If you suspect that your subframe is cracked, now is the perfect time for a front-end restoration project. Personally, I wouldn't even attempt this repair with the subframe still bolted to the car, although I'm sure some have. I would suggest that you support the engine somehow, drop the subframe, and repair the cracks. While you're at it, clean everything, replace all the bushings and ball joints, and put on a nice coat of paint.

Much of the information for this repair came from the BMW 2002 FAQ Message Board.

Will the Weldor

Before we get started, let me introduce my assistant. Will, age 4.

subframe 2

I began by creating paper templates of the braces. I traced the outlines of the templates on the subframe. One of the cracks can be seen in this picture (arrow).

subframe 3

The braces are made from 1/8" steel. With the steel pieces cut to size, they were clamped to the subframe.

subframe 4

Then they were heated with an oxyacetylene torch and formed around the bracket with a big hammer.

subframe 5

I decided that it couldn't hurt to repair the cracks before welding on the reinforcement pieces. I drilled a hole at the end of each crack. The other crack can be seen in this picture (red line).

subframe 6

The cracks were chamfered with a die grinder to make room for a weld bead.

subframe 7

The cracks were welded closed, and the excess weld was ground off. Gasless, or flux-cored, MIG wire was used due to the thickness of the metal.

subframe 8

The reinforcements were tack welded into place, then welded on completely.

subframe 9

Gasless MIG wire doesn't make the prettiest looking welds. I practiced and practiced, but this is about as good as I could do. At least the welds are strong. Once installed and with the engine in place, these welds won't exactly be in plain sight.

subframe 10

A coat of POR-15 made things look much more respectable. POR-15 was also sloshed inside the box sections

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