Re: [xj-s] Dual drive water pump (was overheating)

["Robert C. Warnicke" <Obstinate@worldnet.att.net>]

Mike Morrin wrote:
> 
> At 10:19 PM 7/19/98 -0700, Robert C. Warnicke wrote:
> 
> >I think it is pretty clear that the jag's cooling is marginal, and that
> >post-shut the hot water migration is not fast enough to stop valve seats
> >from dropping.
> 
> I still have not seen ONE shred of evidence that shows that the valve seats
> get hotter after the engine stops.  Even if it were true, and you assume
> that the damage occurs in the minutes or seconds after shut down, have you
> tried to calculate the heat trnasfer you require to cool the engine in that
> sort of time frame.
> 
> I think you are wasting your time.
> 
> regards,
> 
> Mike

No I haven't calculated anything.  I don't calculate well. Every time
the technical types go at it in this forum I get a headache.  I wouldn't
even know how to begin.  Could you calculate it for me?  I was just
going to leave the system on until the temp went down to some
predetermined level, like at what temp does the switch in the water pump
trigger... I was thinking about using that, although I would rather
tigger off the water coming out of the engine, not the radiator.

The only evidence of when the exhaust valves fall is members who have a
fine running engine, then stop it, then on restart it makes huge noise. 
If it fell while running wouldn't it clatter before shut down?

Now if Kirbert's speculation is right, and that the seats are just loose
and are pushed back into place until the valve doing the pushing happens
to be open, and then when the head is so cool it can't push it back
because the head has shrunk, then you are absolutely right this system
wouldn't do any good becuase it only proposes to cool the engine faster,
it would cool and the valve would still be in the dropped position... 

But if it is a post shutdown spike causing the drop... MY car will not
have the customary post shutdown spike becuase the entire cooling system
will be running while NO engine heat is being generated.

Basically we dont know: I appear to be proposing to risk $375 or so to
avoid rebuilding the heads (again: PO had valve seat drop).  Is this
ridiculous... close call.  We will never really know, because if I dont
drop a valve seat, no help, because not everyone does, and if I do, it
could be from heat damage the car has already suffered. (or a
malfunctioning water pump, hose, belt, head gasket, ect)

BTW  The alt shop (since I am adding a fan as well as planning to add
this standby DC motor drive I think more umph is needed for the
electric) thought the dual drive water pump was pretty humourous.  They
recommended removing the engine as well as the lucas alt...  :(

73XJ12  (going to drop a lot of cash for accessories on a engine that
has been sitting for years!!!! argh)

---

References:

• Re: [xj-s] Dual drive water pump (was overheating)
• From: "Richard F. Dixon" <rfdixon@chs.cummins.com>
• Re: [xj-s] Dual drive water pump (was overheating)
• From: Mike Morrin <mikem@southern.co.nz>

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