Tricks for retrieving dropped nuts and bolts that disappear into your engine

We’ve all either done it already or it’s bound to happen soon. The scenario unfolds something like this: You’ve just pulled the valve cover off the engine. You’re holding something, maybe the valve cover nuts, in your hand. You’re about to place them somewhere safe, but as you swing your hand around, you hit something, a nut pops out, and you watch in mute horror as, in slow motion, the nut arcs through the air, does a triple back flip, and vanishes down into the engine. You empty your lexicon of blue words into the garage air, and know that the next several hours of your life are going to be a living hell.

In my case, I’d just pulled the head off the 1987 BMW 535i that I wrote about last month, the one that unexpectedly had a broken rocker arm. Because the head still had both the intake and exhaust manifolds attached to it, it was heavy, so I lifted it using an electric winch suspended from a hook that’s lag-bolted into one of the ceiling joists. After I swung the head onto a pad I’d prepared on the nose of the car, I needed to unbolt the U-shaped bracket holding the winch to the chain that I’d wrapped around the manifolds. After I’d unthreaded the nut on the bracket, I bobbled it, into the air it went, and in an improbable instant, it hit the miracle evil hole in one and skittered down the front lower timing cover.

I stood there, stunned. I shined a light down the recess where the timing chain went, praying that I’d see the nut sitting on top of the crank gear, but it was gone.

When this happens, you have three basic options. The first is, if you know that the item is sitting in the bottom of the oil pan, simply leave it there. The larger and heavier the item is, the more likely it is to just sit in its new home, and the less likely it is to be swept up and carried somewhere to cause damage. Note that I’m in no way advising that you leave items in the pan (let me be clear: Don’t knowingly leave items in the oil pan), but it’s not at all unusual to find nuts and washers in the pan when you tear down an engine. More to the point, once you know that there’s some loose object in your oil pan, I guarantee you that every time you drive the car and hit a bump, you’ll imagine that nut bouncing up, getting caught in the oil pump or timing chain, and grenading your engine.

The second choice is to drop the oil pan and reach in and get the item. Depending on the car, this may be the most direct and efficient way to address the problem. Order a new pan gasket, drain the oil, undo the two dozen or so little bolts holding the pan to the block, pull out the wayward nut (and any other little nut friends you find in there as well), clean it up, put it back together, done. Unfortunately, on the vintage BMWs that make up my harem, you can’t simply lower the pan; the front subframe is in the way, and you can’t slide the pan forward because the oil pump’s pick-up tube hits a baffle inside the pan. On my older, simpler cars, it’s pretty easy to jack the engine up off its mounts to gain the required clearance, but on the 535i the procedure is more involved.

And that brings us to the third option: Fish out the errant item. If the bolt you dropped will stick to a magnet—meaning it’s metal that’s not stainless steel, aluminum, or brass—one of a variety of magnetic wands should help you retrieve it. The wands (search for “magnetic pick-up” or “magnetic retriever”) come in a variety of lengths, in both telescoping and flexible styles, and with magnets of varying size and strength. Note that if you have experience fishing wire in houses, you probably already have fish tape and a snake, and may just need to secure a magnet to the end. Fish tape and snakes may be better able to follow a narrow conduit like a pipe than a flexible wand (he says, eerily foreshadowing events to come).

In my case, I already had a telescoping wand with a strong magnet at the end, but the magnet was too big to fit down the lower timing cover and get past the gear on the front of the crankshaft to where the nut had most likely fallen. Even if the magnet was smaller, the telescoping wand was rigid, which would’ve prevented it from being swept around. I selected a flexible magnetic wand called The Mighty Worm (V8 Tools, item 3826) specifically because it had a very small magnetic head. This is a tradeoff—the smaller the head, the weaker the magnet—but I was simply trying to fish out one nut, not an entire ratchet extension with a socket attached (he says, eerily foreshadowing a second time).

When the Worm arrived, the magnet was indeed small enough to fit past the crank gear. I snaked it down and swept it around, but I wasn’t successful at catching the nut. I then tried going in through the oil drain hole. I hunted around and heard the satisfying thock as the magnet pulled the nut to it, but I was thwarted by the fact that the nut was too big to fit through the drain hole.

I then looked at the bottom of the oil pan and saw the three-bolt flange for the oil level sensor. Saved! I undid the flange, pulled out the sensor, reached back in with the Worm, and triumphantly extracted the AWOL nut. Whew!

And then, because this 535i is that much of a problem child, it happened again. No, not another nut down into the oil pan. The second time, it was an even less probable event.

I had rebuilt and reinstalled the 535i’s head. The exhaust manifolds were on, but I hadn’t yet reattached the downpipes because that required crawling under the car, and I was planning on jacking the car up to do that and some other under-car things. I was installing the spark plugs and had gotten to the last one, number six at the back of the head, when my hand slipped. The plug, socket, and extension dropped. I heard a dull clank. I assumed they’d hit the heat shield or landed on top of the front subframe. But when I looked, I couldn’t find them. I jacked up the car. I searched everywhere. They were gone. Squirted out of the universe like a watermelon seed. Now, as we all know, this happens all the time with 10-mm sockets, but not with three objects collectively the size of a pair of pliers.

And then I saw the open hole of the detached exhaust downpipe. I thought, no way. That’d be like sinking a basketball shot from half court. But there seemed to be nowhere else the plug and socket could be.

These days, for less than $40, you can buy a flexible endoscope (also referred to as a borescope) that connects to your smartphone and allows you to snake a camera and an integrated light source into tubes and crevices. They are incredibly handy. I have an older stand-alone pistol-grip model that my wonderful wife bought me a few years ago. The light source and focus aren’t great, but it gets the job done.

I broke it out, snaked it down the exhaust pipe, and sure enough, I could see the end of the 3/8-inch ratchet extension clear as day. And by measuring the amount of the flexible tube I’d snaked down, I could tell that it wasn’t that far down there, maybe eight inches, just past the dogleg bend in the exhaust pipe.

If this was one of my smaller cars, like a BMW 2002, I could’ve simply unbolted the back end of the exhaust pipe, pulled it out, turned it over, and shaken out the dropped pieces, but on this 5 Series sedan, the downpipes are integral with the catalytic converter, and from there to the back of the car, rust had basically welded everything into a one-piece exhaust. Pulling out the entire exhaust would’ve been difficult.

But no problem, right? Having just survived the nut-in-the-oil-pan incident, I had not one but two magnetic pickup tools at the ready. I found that the telescoping one (with the stronger magnet) wouldn’t work, as it couldn’t get past the dog-leg bend in the exhaust pipe. I snaked the Worm down and thought I heard it and felt it make contact, but its magnet wasn’t strong enough to pull the extension, socket, and spark plug up. Rather than order another flexible probe with a stronger magnet and wait for it to arrive, I cut the magnet off the telescoping probe, zip-tied it to the end of the Worm, and snaked it down, but I still could not pull the pieces up.

I thought, “A-ha! I have an endoscope! I can attach the magnet directly to the end of the scope and be absolutely certain that the magnet is directly contacting the end of the extension!” I tried that, guided the magnet correctly to its target, tried to pull it up, and watched in real time as the zip ties pulled away, leaving the magnet also now trapped down the exhaust pipe. Errant items: 4. Siegel: 0.

This was not going well.

I realized that the problem was that, when the plug-socket-extension trio fell into the exhaust pipe, it wedged itself in place. I almost ran down to Autozone to buy one of those four-pronged mechanical pickup tools to try to grab the end of the extension, but then I thought that perhaps I could take a coat hanger and bend a hook into the end and use that to bring it up. Using the borescope as a guide, I hooked the end of the extension and socket, and although I was unsuccessful in pulling it all the way out, I did dislodge it from where it had been wedged. And, to my delight, when I pulled up the coat hanger, at the end was the magnet that I’d lost. I put the magnet back on the wand, and this time successfully used it to bring up the extension and socket.

The spark plug had fallen out of the socket and back down the exhaust pipe, but now that nothing was wedged in place, the magnetic wand fished the plug out easily.

Whew, a second time!

If snaking a magnet isn’t successful in extracting something you’ve dropped, there’s an additional trick you can try: You can use a very strong magnet on the outside of the exhaust or oil pan to try to pull the lost object along until it comes out a hole. This can be particularly effective if the surrounding material isn’t ferrous (e.g., if the oil pan is aluminum not steel), if you’re not fighting against gravity, and if the item isn’t wedged in place. In addition, a friend who is a lineman tells me that there is a whole other wizard level of tricks, one of which is snaking a deflated balloon and an air supply down a pipe, partially inflating the balloon to catch the item, and pulling it up. It’s comforting to know that there’s always someone with a bigger problem and a deeper bag of tricks than you.

In the meantime, I will try not to carry anything in my hands within several feet of an open engine, and to plug open exhaust pipes with rags while working.

Who am I kidding? That discipline will last two days, tops.

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Rob Siegel has been writing the column The Hack Mechanic™ for BMW CCA Roundel magazine for 30 years. His most recent book, Just Needs a Recharge: The Hack Mechanic™ Guide to Vintage Air Conditioning, is available on Amazon (as are his previous books). You can also order personally inscribed copies here.