I was just viewing an European site and the terms tick-over and over-run were used while discussing blue smoke from the exhaust. It said if you see blue smoke during tick-over it's probably the rings and if you see blue smoke during over-run it's probably valve stem seals or guides. Does anyone know what these terms mean?

Thanks,
teeman

From the context of what I've read in this forum, tick-over is just when the engine catches/starts and settles to idle.

over-run = ?

Sixto
93 300SD

Overrun = coasting (using the engine like a brake, or when you coast downa hill with your foot off the gas and the speed is just right)

I'm not so sure you can tell if when you smoke that it's rings or guides. After all smoke is smoke.

Usually valve guide smoke was what you'd see with high-vacuum in a gasoline engine, closed throttle overrun such as downshifting to slow down, then a puff of blue when you shift or get back on the throttle. In a diesel there is no high-vacuum situation so it is much less obvious, and doing a leak-down compression test is more difficult also.

- Jeff Miller
190DT