Can I resurrect my tyre compressor?

[pepper]

I've got one of those 12V tyre compressors which has become next to useless over the last couple of times of using it. The electronics still works, (you can set the required pressure, and it reports the current tyre pressure), and when you turn it on it makes its customery racket, but the tyre pressure doesn't get any higher however long you leave it. Opening it up reveals not much more than a smallish electric motor connected to a piston in a small cylinder about 1cm diameter by 2cm long. There's no obvious splits or leaks in the hose or anything, so I'm assuming that the piston is just not as good a fit into the cylinder as it was when new. Is there anything that can be easily done to give this a few more months life? Will a couple of drops of oil help to form a seal between the edge of the piston and the cylinder? NB. Cylinder is metal, piston appears to be nylon, crank shaft and drive to motor metal.

Any ideas?

[Adrian]

pepper gurgled happily, sounding much like they were saying:

Bin it and buy a new one. They're only a few quid. Don't bother with one with the pressure-monitoring electronic guff, especially since they're about as accurate as the weather forecast.

[Tabby]

Oil should really help if that's where the problem is. It could just as easily be the valves. You could oil those too, though how long that'd last I don't know. I'm just wondering what oil thickness to use.

NT

[PeterC]

Grease is better than oil, at least where the air flows, as oil can be carried in and degrade the rubber. This is more of a problem with bike pumps as they get very hot in warm weather (too hot to hold sometimes) and there's only a thin tube.

[John Williamson]

These compressors are built to be cheap, not to be easily repaired. The pistons and cylinders wear rapidly, and the valves are basically just cheap non-return valves, which normally work by a soft plastic bit sealing onto a hard plastic bit, held in position by a weak spring. The springs could be broken, or the seal could have failed.

If you get more than a couple of hundred tyre inflations out of them, you're doing well.

[Dave Liquorice]

When my "tyreman" failed it was one of the one way valves that had failed. This was simply a flap of thing springy metal that sat across the inlet hole to the cylinder. It was bent so didn't seal. I can only assume that it didn't spring shut quick enough and got whapped by the piston.

Dismantle the compressor a bit more and see what the valves are like.

I'd not use oil, the compressor will get very hot and oil vaporise and or become very thin and be carried into the tyre. Wether that is a problem I wouldn't like to say, urban legends about oil degrading rubber etc. Any lube would best be done with the merest smear of a high melting point grease.