Re: UR-q blue smoke.

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <9809071549.AA06174@grommit.swan.ac.uk.swan.ac.uk> ggthack@swansea.ac.uk (Graham Thackrah) writes:

> I'd be interested in knowing how to perform a leakdown test on my car.
> The reason is that I have a smoke problem that was put down to valve stem
> seals but wasn't solved on having them and the guides replaced. It doesn't
> noticeably smoke more or less when warm or cold.

You need an airline, an adaptor for the spark plug hole, and some sort
of pressure limiter.

> The problem is only on overrunning; a brief puff on very hard up changes
> (c. 6500 revs) and when decelerating from high revs (such as lifting off the
> gas on the motorway or going down hills off the gas). I'd like a good idea
> of the likely source of the problem before I go ahead and take the head off
> again or remove the engine to have a rebore.

I hate to say this - but that sounds _very_ much like a valve stem leak
and not very much at all like anything else.  You can't replace the
valve guides without doing the seals, because it's pretty hard (a.k.a.
impossible) to get the seals off without destroying them.  It's also
very hard to get the job wrong - the seals are _really_ easy to fit and
next to impossible to fit incorrectly.

Do the symptoms change with engine temperature?

My suspicious mind is tending to the view that the guides _weren't_
done.  It's a non-trivial job, BTW, even with the right equipment.  If
the guides are very badly worn and new seals are fitted, the new seals
will last less than 1000 miles.

--
 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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