Warm astra td won't start

Valve Clearances?

Some manner of temperature sensor? Water probably? I know nothing about diesels except how they work.

Si

reset the valve clearances

"MrCheerful" wrote in news:8lYIh.100415$1E3.49581 @fe3.news.blueyonder.co.uk:

Question for Mr. Cheerful etc. When the engine in a car is hot are the valve clearances lower or higher? IE. Do the valves open further when cold?

Valve clearances tend to get tighter when warm, due to the fact the valves are the hottest part in the valve train, and expand more than the other components. More so with the exhaust valve, as they don't get the benefit of the inlet air to cool them.

This is a common problem with this engine. In this case the clearances become less, hence the compression becomes less (if they are even a tiny bit held open) , you find that a tow will usually start them in this condition, the engine spins fast enough that the compression doesn't have time to sneak past the valves and away the engine goes, till you stop and try a warm start again.

So yes, valves do open very slightly (almost unnoticeable in real terms ) earlier and to more lift and for slightly longer when hot. Other engine designs and materials could mean the clearances get more, but not this engine.

Mrcheerful

It threw me when I first found that a hole in a solid block of metal gets

*bigger* when you heat the block - intuitively, the metal expands so the hole *should* shrink. But apparently not.

In valve clearance terms, of course, it's much more complex and depends on all the various materials and geometries present...

I rememember doing an experiment at school about that. Intuitively you would think a hole would get smaller. However if you think of the metal surronding the hole as being a couple of strips of metal bent round into a circle, an inner strip and and outer strip. Then if you heat them both strips have to expand, the only way the inner strip can expand is by getting larger thus making the hole bigger.

"Mungo \"Two Sheds\" Toadfoot" wrote in news: snipped-for-privacy@pipex.net:

Heh...a contradiction in terms, if ever I heard one ;-)

Stu

:o) It's the theory/practise interface that's lacking in my case.

Si

So how do I reset the clearances? what are the correct settings?

You'll either have to get a Haynes manual or let your friendly local garage do it. It won't cost much.

Si

Question for mr cheerful or anyone else who might know. Wht should the valve clearance be? How do I go about it? Thanks, Steve

Sorry, forgot to mention, it's a Vauxhall engine, not an Isuzu

If it is the Vauxhall engine then there is no provision for adjustment, they have hydraulic followers.

In that case I would be looking for low cranking speed, air leaks, retarded injection timing or low compression (in that order)

So how do I reset the clearances? What are the settings? P.S. it's a Vauxhall not an Isuzu

I'm not being funny but if you have to ask about this, and haven't got/won't get a manual to work from, you shouldn't try to do it yourself. Either get a manual and read about valve clearances or take it to a garage.

Si