This pic is my avatar Merc, driverside motor mount. It has pulled away from the frame rail and has a few hairline cracks. My game plan is to try and repair this without having to pull the motor. First, weld the hairline cracks. Then cut the gusset off at the frame wide enough to slide about a 5 inch long or so plate to the frame and re-weld the gusset to the new plate. Thoughts?
First you need to clean the area to be repaired . Drill holes at end of each crack , grind out a v shape and the weld up . You maybe better with a piece of angle welded over your repaired area to spread the load. Do not go thin on on the angle. I get you not wanting it to get very involved but I would cut out everything and weld in a fresh frame section and make up a new mount with load spreading plate and gussets . That steering suspension piece I would give it a once over where it was welded just for safety/piece of mind if your are using it .
I would cut that gusset off and add two, one on each side of the pad and across the width of the frame.
It's ambitious to try to do this with the engine in place but if I was doing this repair I would want as much room as possible to get in there to do it up right.
If that's on the side where engine torque pulls the mount, you need to spread the area where the weld is on the frame. Once repair is done. you could add a torque strap to help the engine mount with the torque reaction forces.
First off, those lines you are calling "hair line cracks" are not cracks, but failed steel and are entirely through the thickness of the frame rail, at two different locations, as well as almost entirely around the existing gusset. JI tell you this just in case you don't have the full concept of what you are dealing with. Currently, all that gusset is doing is flexing in and out of that section of the frame rail and stressing the other part of the mount. Minimum repair would involve stop drilling a hole at the end of each "crack", grinding a "V" on top of each "crack". Then you need to clean the edge of the gusset, all the way around the base, put it (the gusset) back into position (its currently pulled out of the base metal) and reposition it to the correct position. Then everything would need to be welded. A better fix would be to cut the damaged section out of the frame (including part of the top, the side, and the bottom of the rail) and replace that section with a new piece, then redesign the motor mount gusset to spread the load out to at least the width of the top (in the picture) surface as well as that side surface that is damaged, and the bottom of the frame rail, or with a mount that connects to the top of the frame, and two full length side gussets, one on either side of the motor mounting point. You also really need to inspect the other part of that motor mount, I suspect at minimum the other bracket that extends out from the frame may be fatigued and possibly have cracks in it, and I would also inspect the welds surrounding that piece as they may be damaged as well. That piece that extends off the frame has been bending up and down for as long as the side of the frame has been damaged and most likely needs repair also. Once that was completed, you have to cure the problem. The problem is that the gusset was added to the mount into the side surface of the frame wall at a location that was never intended to be placed under that strain. It appears to have put up a good fight for a long time before it failed. That gusset needs to be welded to two sides of the frame, the side that failed, and the top (in the picture) side so the load is spread out farther. That motor mount should actually have a gusset on each side of the motor mount that is attached to two sides (three would be better) of the tube frame. Accomplishing all that needs to be done could be very difficult with the motor in the way. The pictured don't really show how much work space is available. Repairing the side of the frame rail is going to require a lot of uninterrupted work area, and that may not be available without removing the entire motor mount. At my shop, I'd want the motor out of the car. Repairing a frame rail that has had a chunk torn out of it is serious work, its not something I'm going to cut corners on. Gene
I’d cut that gusset out , repair the hole that’s left and make a new triangulated box section gusset that covers abit more area. It only needs to be the same thickness as your chassis material also, that thick gusset is a waste of time on thin material , imho. Over engineering at its finest. Good luck if this can be done with the motor in place.
I wouldn't worry about the existing gusset, and I'd just abandon it. I'd box the mount in by welding side plates, and then a top plate that laid on top of the frame rail. It wont ever go anywhere once it's boxed in.
The Jalopy Journal
