Lost Motor Mount Nuts in Frame

[Urambo Tauro]

1995 GMC Sierra SL C2500, 295,000 miles

So I noticed the air cleaner assembly in my truck was leaning, which meant that the engine was leaning too. Motor mount time!

It wasn't fun, but I finally managed to get the new ones lined up and bolted up- except for two nuts. Working from the small gap between the frame and lower control arm, I couldn't get a socket wrench to fit the uppermost mount-to-frame nuts (inside the frame), not even through the use of extensions or swivel joints. So I used a long open-end wrench instead. It worked, and I very gently lowered the nuts down out of the frame without dropping them.

Unfortunately, when I went to fasten the new mounts in place, I dropped the nuts somewhere inside the frame. Not all of them, just two. I continued working anyway, borrowing one of the other nuts and gently feeding it up into the frame via the open-end wrench, and carefully threading the bolt into it. I now have two fasteners securing either mount, both an upper bolt and a lower one. That leaves one more lower bolt left to tighten on either mount.

I've tried fishing around in there with flashlight, magnets, and blindly trying to squeeze my fat fingers in there. I can't find the nuts at all, much less reach them. And there are some sort of baffles/reinforcement inside the frame in different spots so it's not a straight shot. I'm not sure what corner they could have fallen into.

Anybody familiar with the internal geometry of the frame that can comment on where the nuts might have rolled into after falling from the top motor mount bolt? I know they're still in there somewhere, but I'm seriously about to give up and just get some fresh nuts from the hardware store instead.

 

[delta_p]

I don't know what's in the frame but I think your idea of going to the store for a bag of bolts is a good idea. Have you done this with the engine in. I am wanting to do this to my C1500 and figured it would be a PITA lifting the engine and get in there. Wasn't sure if i'd have to remove the exhaust manifolds for room.

I started to find some vids to work up my courage. Most of them seem to put the nuts back on the top side.

He fishes the bolts in at 2 minutes 34 second mark in first video.

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[arrg]

Just stick one of those telescoping pen magnets in there and go fishing. You'll find them. Them bottom of that crossmember is pretty flat.

 

[Urambo Tauro]

I have one, and it fits inside the frame, but I can't feed it in from above to scour the bottom of the frame. If I feed them in from the bottom, it's telescoping upward, away from whatever surface the nuts fell on. I though about getting a flexible magnet, but I think it would just flex around while the magnetic head stuck to the frame.

I also have a claw-type pick up tool, but I need to know where the nut is before I can grab it.

The way the frame angles up away from the crossmember leads me to think that the nuts fell somewhere over the lower control arm mounts. But there are some sort of reinforcements/baffles above where the LCA mounts to, which could have caught the nuts. This pic is looking at an upward angle from underneath the front of the truck (passenger side), directly at the forward LCA mount:

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[Urambo Tauro]

I don't know what's in the frame but I think your idea of going to the store for a bag of bolts is a good idea. Have you done this with the engine in. I am wanting to do this to my C1500 and figured it would be a PITA lifting the engine and get in there. Wasn't sure if i'd have to remove the exhaust manifolds for room.

I started to find some vids to work up my courage. Most of them seem to put the nuts back on the top side.

He fishes the bolts in at 2 minutes 34 second mark in first video.

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Yeah, I found mine bolted from above with the nuts inside the frame, so I tried to put it back together the same way. I'm probably the first to change these mounts on this truck, so that must be the factory way of fastening them. If I had fed the bolts up from underneath, I'd probably have better luck finding them right now.

I'm thinking that if I just leave them in there and use new nuts instead, the old ones will either stay lost in the frame forever, or they'll randomly bounce out somewhere down the road. The nice thing is, they're nuts, not bolts. So if they do fall out, they won't present as much of a tire puncture hazard as a bolt might. Harmless as the rest of the gravel road I live on.

 

[Dr.Zoom]

There are telescoping magnets with heads that swivel/angle. But it sounds like you're getting new nuts anyway.

You can put a piece of tape on the back side of the wrench when you're installing them to keep the nut from falling through and it'll stick a little to the nut. Maybe even a partial wrap of tape on the nut to make it snug

 

[454cid]

Try a piece of hose/fuel-line on the end of a vacuum cleaner, and go fishing.

 

[Urambo Tauro]

Well, I gave in and bought some new M10x1.5 nuts. I couldn't find flanged nuts like the ones I lost, so I installed them with washers. Good thing I saved the easiest ones (rear lower on both mounts) for last. Thanks anyway for the suggestions everyone. This job was a PITA, but if I ever have to do it again, I think I'll try threading the bolts in from underneath.

 

[Jglew82]

Glad you got that sorted out. I'ts a PITA for sure. I did mine when I rebuild my entire front end, so I didn't have to contend with the LCA's. Previously, on a different truck, I pulled the bolts up from the bottom using a coat hanger and electrical tape and put the nuts on the top. Definitely much more difficult than the old C10's.