Jonathan Minns practically makes a fetish of groaning gears, heaving pistons, and ecstatically rotating flywheeels. He recently presented to the city of Vienna four massive engines he had restored for the city's new technology museum - and preached with drawling relish to bemused Austrian dignitaries about "the rabid sexuality of steam". A Teutonic approach would perhaps have been more ponderous, but Minns likes to do things with a flourish - in this case, dry ice theatricals and video projections. Then, with gusto, he fired up the engines themselves. "They get so damned serious," he confided later, referring to the assembled officials.

Tall and striking, with one of those booming, throaty public school voices which easily carries across a crowded exhibition room and straightens people's spines, Minns has been variously an underwater archaeologist, an actor in Paris, a rancher in Mexico, a London plumber, a television presenter, a consultant on mechanical antiquities for Christie's, a museum founder, and a judge for 18 years for Prince Charles's awards scheme for industry and innovation.

He also is mad about Ireland, having spent happy weeks dabbling in Robert Guinness's collection of old engines on display at Straffan Lodge back in 1965, while writing his first book on 19th century engines. He goes rhapsodic about Birr Castle, where he spent time three years ago discussing the development of the castle as a scientific attraction. "The park itself is in my view of enormous scientific importance," he says. "It was the first scientific park . . . " And he's off, dreamily listing its attractions, from water systems to its vast collection of trees.

But at heart he is, most extravagantly, an engineer, a calling he answered at 14 and which is clearly closer to a priestly vocation than a career choice. His father was an engineer, and his uncle was Sir Christopher Cockerell, inventor of the hovercraft. "Engineering is the international language of making and doing," he says. "Engineering is the art that works. Beauty is a conscious decision."

Nothing is more beautiful, to his mind, than the flywheels, pistons, valves and gears of the engines created in years gone by. They induce a kind of giddiness - he rushes around his four enormous engines in Vienna, some dating back to the 18th century, like a small boy with his first train set.

He explains how missing flywheels, melted down for armaments during this century's wars, had to be recast, and internal engine parts meticulously cleaned of centuries of oily grime. One engine was found in a mouldering barn, another in an ancient hospital.

Now the machinery glistens in a pristine white display room, and can be fired up for visitors, a process which induces another fit of excited description. The Vienna Technical Museum, which will open in a year's time, is the 28th museum Minns and his support crew have done work for, either conserving relics from engineering's past or, if appropriate, restoring them to full running order.

Minns obviously most enjoys the latter. "When you bring back something which has lain silent for many years, you realise it is a living thing," he says with great seriousness, tenderly eyeing the old hospital air compressor. His conservation and restoration programme, which features a five-year apprenticeship, is run out of the British Engineerium, a museum full of working steam engines he helped found in 1975 in Hove.

Housed in what was a derelict Victorian pump house, the museum now contains road, rail, marine and stationary steam engines, hot air and internal combustion engines, and domestic tools.

Minns's passions now are focussed on a three-year engineering course at Brighton University on technology conservation which he has helped design and which launches next September. The modular course will, he hopes, bring together students of all social backgrounds and teach them to do more than the "pure interpretation" of industrial archaeologists.

He wants them to be able to rationalise the conservation process, and "ask the right questions". Primary amongst those is whether an object can, and should, be restored to working order. "Part of the decadence of moving away from the post-industrial age is we've lost touch with moving objects. We're losing touch with three-dimensional thinking," he says. Skills passed from one worker to the next are dying away, and museologists think only of saving the object, complete with rust, which infuriates him.

"Pure interpretation is not enough. Someone has to get their hands dirty," he says. He points, deploringly, to the increasing tendency of science centres like London's Science Museum to put the real mechanical objects in storage and instead offer multimedia interactive displays. "We shall end up with international science centres with the same feeling as the product displays in an airport," he booms. If any voice can get decision-makers to listen, it's certainly his.