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Forg's Dark Corner

2nd April 2002

By Matt Cremer

Click on pics to view larger images


An Ode To A Screw Extractor

When the brass pipe broke,

You were there for me,

Yet 'twere in too tight,

Should've been plain to see.

So I torqued too hard

And you tried to help

The strain was too much

You snapped without a yelp.

Yes, folks, that's right. Project cars do send you insane. I'm living proof of the fact; before this while thing started I was actually sane, and have a certificate somewhere to prove it [rustling sound of digging-around in drawers] ... I know I did have one until recently [more rustling sounds].

But bugger that, I'm now technically as loopy as a thing with lots of loops in it, and for that I blame Project Volvo. OK, OK, maybe my own ineptitude's at fault somewhere in there, but I shouldn't have to wrestle with the stupid thing every time I want to tighten up a bolt ...

It all started like this [wavy Wayne's World dream-sequence cut]. It was getting a bit late in the evening, I'd finally finished under the back of the car, and had about half an hour before it was time to finish up. Thinking about what small things needed to be done, I figured I'd install the water and oil sensors.

Not having a factory oil-pressure gauge, it seemed a good idea to install a (name-brand) adapter that allowed me to run the factory oil-pressure switch (for the dummy-light) as well as the aftermarket oil-pressure sensor (for an aftermarket gauge I've installed; the originals are all VDO, and VDO still make gauges with the same typeface etc, so extra aftermarket gauges are a neat and easy drop-in).

Anyhow, the water temp sensor screwed in quite nicely; another hole in the engine plugged-up, and one less hole for a spider to live in as well. The oil-pressure sensor hole wasn't quite so easy to find, mind you, but a combo of the factory service manuals (I recommend the factory manuals to anyone doing a project car they're not au fait with, the things are just brilliant) and looking at the old engine allowed me to find the spot; it's about halfway between the oil-filter attachment and the front of the block. Beauty; grab the brass double-adapter piece, and start screwing it in.

After only a couple of turns, it starts getting a bit tight. So out comes the socket set, and I start winding it in again. Now, OK, it may have been a bit tight, but it really didn't feel tight enough to justify the snap-clink-tinkle that followed soon after.

Shit. Shit. Shitshitshitshit expletive oh shit.

Yep, it sheared off alright, and quite flush to the cast-iron of the block. After some constructive work with the mallet on a few items around the garage, I remembered that my father had some tools that might do the trick; an easy-out or screw-extractor. So I drove over there, asked where he kept the tap and die set, got home, realised that I didn't want a tap and die set, drove back over, grabbed his screw-extractors, and drove back home again.

Fortunately the piece of brass already had a hole in it where the oil for the pressure sensors was supposed to go. Oh, and if you aren't aware, a screw-extractor or easy-out is simply a reverse-threaded tapered piece of hardened steel, and as you screw it in into the broken-off piece it's supposed to grab and spin the broken-off piece out backwards.

Supposed to.

With a screw extractor you have to be careful, especially with a small one; because if it snaps, you've got buckley's of drilling it out - it's hardened. With stuff like brass it's even worse, because the softness means that the screw-extractor expands the brass, so it grips even harder. In summary, you probably shouldn't attack it with a 12-inch shifter like I did.

"Snap".

"AAARGH!" More mallet usage, more breakage elsewhere in the garage. This is gonna get bad ...

Next day, I called the friend who runs the workshop in the nearby servo; really nice guy, he'd do just about anything for you. He came around and had a look, and thought there had to be a way of doing it. The screw-extractor itself had broken off flush with the broken piece of brass. We tried to use a punch to spin either piece around to back them out of the hole; no help. Fortunately there was enough meat in the brass left that we could drill at various places around the screw-extractor and pull the screw-extractor out that way; we snapped at least one drill bit off doing it, but at least it came out.

Oh, I've not yet mentioned the fact that we'd pulled a plug off the front of the engine and were blowing compressed air up the oil-filter pipe. That way, we figured any filings would be blown out the front of the engine. What fools ...

Anyway, with the use of the drilling, a magnet, the compressed air and a bit of luck, we managed to get the drill bit and screw-extractor out of the brass, enlarge the hole a bit, and get ready to try with a larger screw-extractor. This time we used only a 4-inch shifter; that way there was little chance of snapping off the quite-thick screw-extractor.

"Tink". It snapped like chalk.

I gave up; forget it. Come back in a couple of days, when there's been time to think about it.

The solution was just to pay someone to do it. I had no idea of how to find someone, but I did get some recommendations - they're listed as Thread Repair Engineers or something similar, but you can't really tell what they do from the phone book.

I organised it for a time I wasn't there, so I didn't get to see him do it. He attached the compressed air to the same spot, he apparently did some drilling, and he may have used a diamond drill (the exxy Snap-On carbon drills we were using had only made a tiny dent in the exposed tail of the easy-out). But the result of his work was - ka-ching - the hole was free and clear for me to screw up again.

Except ...

He had a quick look down the hole in the front of the block, and you could see an oil-gallery leading downwards. Downwards towards, say, the front main bearing. I looked it up in the service manuals, and the concept drawing showed that there was a gallery down to the main bearings there; a very helpful American chap on a Volvo-specific email list went out to the garage on a cold night and blasted away at an old block with his oxy torch and confirmed the existence of this gallery in that location. The thread repair guy had seen some shit still in the oil-gallery, and reckoned there was a chance that something may have tumbled down that gallery. If so, the chances of lunching the bearings the first time the engine's turned on are way too high for comfort.

*sigh*

Anyway, the upshot of all that is that the engine has come out and been pulled apart. I looked into the hiring of a boroscope or an endoscope (much like a medical arthroscope, a camera on the end of some flexy optic fibres), but the corners on the oil-galleries are too tight for the cables to go around. Apparently aircraft engines are designed with galleries everywhere for these inspection devices; oh how I wish mine was.

The sum total cost of my mistake so far? Well, including the thread-repair guy and the rebuild of the engine, we're talking close to ~$1k. Admittedly, if I'd had the room and tools to do it at home the rebuild would've only cost me the price of gaskets; but I don't. $1000 wasted just because of a stupid mistake ... still, it could've been worse, the engine builder reckoned he found and removed all sorts of crap in there ...

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