crack driver side front subframe got me

[bey]

Hello all,

My 1974 2002 subframe develope a crack right below the left side

motor mount. Does any one know what gauge steel is needed to

strengthen and repair the subframe.

[c.d.iesel]

. ...IF IT'S JUST A 1/4" - 1/2" IN LENGTH -

just moitor it and wait till it really grows

to be of concern. Any gauge clean metal welded over the crack and gusseting is good . Important part is cleaning to bare metal and

checking the repaired bracket for clearance with the steering box

and mount .

[Rob7502]

I would recomend no thinner than 16 gauge. Also before you weld over the crack Drill one small whole at the end of each crack, this will prevent the crack from spreading out from under your patch.

[jimk]

The best reinforcement is to modify the mount from a u channel (in cross-section) to a box section. The reason this one cracks is that it restrains the rocking motion of the motor and flexes first in compression then in tension.

The inclination to weld straps up and down the sides of the channel don't place enough strength in the right spot.

A simple formed plate across the open side of the channel adds much strength in the flexing area. Martin's site may have something on it, as we have fixed at least two this way.

If Marin's site doesn't have a photo, I have one.

[Gordon]

Take a look at this picture, it shows where you need to reinforce the subframe on a 2002.

http://www.coupeking.com/product_main.php?product_id=312&image_id=1126234078

[jerry]

I recently reinforced two cracked subframes by welding a small metal plate approximately 1/8inch thick as shown in the first photo. I used a small jigsaw to rough out the piece then molded it with a ball pien hammer and file.

As it took approximately 30 years (and 150K miles or more) for the crack to grow approximately 3/8 inch I considered the stresses low. This plate transmits the bending stress as shear loading across the newly placed weld bead.

Note: the engine mount was originally fabricated from a steel stamping. The edges were not chamfered (beveled) and thus consisted of a rather sharp edge which is VERY suseptible to crack initiation and subsequent crack growth.

If you have the opportunity I strongly recommend that you take a file or stone (sandpaper will work too) to the edge of the engine mount and lightly dress the edge to remove the burr. IF and I stress IF a crack hasn't initiated, this will serve to extend the cycles to crack initiation.

[bey]

Thank you jerry