You may recall that last autumn I had a ’74 2002tii drop into my lap. I was at German Car Day at Larz Anderson Museum in Brookline, and a gentleman parked the car on the lawn right next to my E9. We chatted, and I learned that the car, owned by him since 1977, was now for sale. I went over to his house about a week later in an advisory role, and told him what I thought the car was worth if he did a few things to it, and what it might be worth to someone like me if he didn’t. I saw a very faint sheen of oil in the antifreeze that could’ve been indicative of a weak head gasket. I factored that into my thought process, but because the car ran fine, it wasn’t a big glaring red light to me. One thing led to another, and I wound up buying the car for what was a fair price to both purchaser and seller.

The last thing the owner said to me before I drove it away was, “His name is Otto.” When someone has owned a car for 38 years and tells you his name is Otto, you call it Otto, or else risk angering the Automotive Powers That Be. (Note that I said “it.” I’ll do automotive proper names, but I generally draw the line at gender-specific pronouns.)

Otto and I are getting along right well.

It has a bit of rust, but its Polaris paint and blue interior are very presentable. And right out of the box, the car ran incredibly well, with the tightest steering of any 2002 I’d ever owned. It was also surprisingly good in terms of clunks and rattles. I insured it not with Hagerty, but on my regular policy so I could legally daily-drive it from my house in Newton into work at Bentley Publishers in Cambridge.

And daily-drive it I did. For four months, until just before the holidays, it was glorious. I was the guy with the Cheshire Cat smile heading to and from work in the 2002tii, at least every day it wasn’t raining. (On those days, I drove my Z3, which made a warped kind of sense.) It was the first time I was daily-driving a 2002 in at least 25 years. It felt like my third or fourth childhood. (I’ve had many childhoods I’ve lost track.)

Using the car to commute in local traffic, I quickly grew to appreciate the diving-board bumpers that are stock on US-spec square-taillight 2002s. The first week of our relationship, I got tapped from behind; it was the sort of tap that would’ve made you cry if you were driving a ’73 or earlier car with pretty but useless chrome bumpers, but in Otto, I didn’t even get out of the car; I just gave the guy behind me a dirty look.

I enjoyed all this enormously until I put the car away right around Christmas. I forgot all about the oil sheen in the coolant.

Until last week.

I was preparing to put Otto up for sale. I hated to do it, but with thirteen cars and my son Kyle getting married in a few months, there seemed to be a nice symmetry around letting one of my metal children go so that I could I could help out one of my actual flesh and blood. Otto was the best candidate.

I wrote up my customary insanely long eBay auction, with photographs of every square inch of the car, top and bottom, inside and out, good and bad. My philosophy has always been to show, in excruciating detail, all the things that any 2002 buff can suss out in two minutes if the car was in front of him or her. This isn’t just me being a Boy Scout; showing what something actually is removes the question of what it might be. Do that and you remove risk for the buyer. Remove risk, and the number of bids increases.

Along that line, I customarily not only take compression readings, but photograph the compression tester on each reading, with the engine compartment of the car plainly in the background. That way, they’re not just claimed numbers; when they’re photographed, there’s little question that those are actual compression readings for the actual car. I do this despite what I say in my first book, that I’m not a big fan of compression tests because they rarely tell you something you don’t already know. For the most part, if a car runs smoothly without clouds of blue-gray acrid oil smoke or sweet-smelling whitish antifreeze smoke out the tailpipe, it’s pretty rare to find a compression number that surprises you.

There’s the windup. Here’s the pitch.

So I’m measuring the compression on Otto. Imagine my surprise when Cylinder #1 reads 150 psi, #2 is about the same, but when I get to Cylinder #3, it reads 45.

Huh?

Whether in science, engineering, or automotive endeavors, when you get odd data, you redo the experiment. I grabbed my other compression tester, but found it had a bad Schrader valve; the readings wouldn’t stick.

So I went for the leak-down tester. Like the compression tester, you screw a leak-down tester into a spark-plug hole, but first you position the engine so that the cylinder is at top dead center with its valves closed (so it should hold air), then hook a hose from a compressor to the inlet side of the leak-down tester and compare the pressure of the air entering the cylinder with the air leaving it.

In practice, as long as the numbers aren’t zero, I haven’t found the leak-down numbers themselves to be all that useful—unless a vintage car has a freshly rebuilt engine, I’ve always found the leak-down numbers to be abjectly horrible—but the test is helpful in several other ways. Simply using your ear, you can hear where the air is escaping. Usually it goes into the crankcase and is audible through the holes for the oil cap and the dipstick, indicating wear in the cylinder walls, rings, and lands. If it comes out the exhaust, you have a burned or bent exhaust valve; out the intake manifold, a bad intake valve.

How a bad head gasket presents itself to a leak-down tester varies with the failure mode. People refer to a “blown head gasket,” but a head gasket can go bad in one of five basic ways. “Blow” usually refers to the first two failure modes, as they’re the most spectacular.

  • If the gasket fails between a cylinder and the outside world, you hear a ton of noise when the engine is running, and on a leak-down test, you should hear air escaping between the head and the block.

  • If it blows between two cylinders, it’ll probably sound like the Devil’s diesel with the engine running, and on a leak-down test, you should hear air escaping out the spark-plug hole of the now-joined-at-the-head-gasket cylinder.

  • If the head gasket degrades between the coolant and oil passages, you’ll get coolant in the oil or oil in the coolant, or both, but you may not see symptoms of it in the leak-down test.

  • If it degrades between the cylinder and an oil passage, with the engine running you’ll probably see substantially increased oil burning as oil is forced into the cylinder.

  • But if the gasket degrades between the cylinder and a coolant passage… ah, then the leak-down test is a thing of beauty in terms of crystal-clear, unambiguous diagnosis. The air pumped into the cylinder goes into the coolant. If there’s a small leak, you’ll likely see bubbles of coolant if you open the radiator cap (you’d likely see this if you opened the cap with the engine running as well). But if it’s a large leak, the cooling system will gurgle like an office water bubbler, as attested to by the sound on the video I shot of the leak-down test on #3 cylinder.

I’m not thrilled with having to spend the next few weekends replacing the head gasket (and yes, I’m quite well aware that Paul Wegweiser and Ben Thongsai changed one in the parking lot of the Vintage in 2012 in one hour and 56 minutes). But it is pretty cool to hear my coolant gurgle.

As the Queen of Hearts said in Alice in Wonderland, off with his head!

Damn! I just used a gender-specific pronoun to refer to Otto!

(Next week… well, I think it’s clear what I’ll be doing.)—Rob Siegel

Rob’s book Memoirs of a Hack Mechanic is available through Bentley PublishersAmazon, and Bavarian Autosport—or you can get a personally inscribed copy through Rob’s website: www.robsiegel.com. His new book, The Hack Mechanic Guide to European Automotive Electrical Systems, can be pre-ordered from Bentley Publishers. Use the coupon code “BMWCCAELECTRIC” for 30% off list.