[xj-s] overheating, the right solution

[Juliansean@aol.com]

In a message dated 98-07-22 04:46:13 EDT, mikem@southern.co.nz writes:

<< I still have not seen ONE shred of evidence that shows that the valve seats
 get hotter after the engine stops. >>

The seats themselves cannot get any hotter.  There is no energy being put into
the system after shutdown.
BUT, the surounding aluminum head material is at a constant 195 F (or whatever
the thermostats are rated at) immediately after shutdown.  When the coolant
stops moving the temperature gradient is reduced between very hot combustion
chamber, valve seats etc. and the rest of the head.  So, the very  hot metal
cools a bit, but the rest of the head temp. increases.  Expansion of the
aluminum head causes the seat to drop, not the temperature of the valve seat
itself.

Having said all that, I still agree with your statement that post shutdown
water circulation is not the right solution.  I think that really making damn
sure your car is running at a CONSTANT temp. determined by the stats is the
way to go.  This includes rodding the rad, ensuring pressure retention (rad
caps small leaks etc), checking the coolant recovery system, and possibly
replacing the 190 F stats with 180 F stats (Chad recommends that I, believe). 

I am in the middle of perfecting my electric fan replacement for the mech.
fan.  It is definately a marginal system and everything has to be just right
to be confident that constant temps are maintained.   The easy way to tell is
by just looking at the stock temperature gauge.  If it remains ROCK SOLID at
the same level no matter what ambient temp. is you can reasonably assume it is
maintaining constant temperature.  If it goes up and down a bit, even if it
stays below the N then your engine is NOT keeping a constant temp.  This means
only one thing: the stats are wide open, the cooling system is at max.
capacity, and the temp. not controlled at all.  
When I hear folks on the list talk about temp. gauges that moves up and down a
bit but that they feel OK because it does not go above the N I think they
should realize that they are probably getting hotter than rated temp.  I have
proven on my car the needle in the middle of the N corresponds to a water
temp. in the cooling rail of 210 F, even with 180 degree stats.  I don't care
what I have to do, I'm going to make that system run at 180 even when it is
110 outside , like today :)

Julian Mullaney

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