[xj-s] maybe it's the water pump (ubuiquitous overheating problem)

[Juliansean@aol.com]

I get the needle creeping up towards N in traffic too, and I have replaced
EVERYTHING so it's not anything wrong with the car.  

I found an interesting bit of data:
I have found that if I absolutely floor the car (like from standstill to 6000
rpm shifts) after it has already crept up to the N then the gauge drops very
dramatically.  This is counterintuitive because you would think a heavy
acceleration like that would dump a buch of heat into the cooling system and
make the temp. go up not down.  

Posssible explanation:  the car is idling in traffic and heat accumulates in
the coolant in the cylinder head and other hot areas but the rpm of the engine
and water pump is low.  So the water is not circulating very fast.  This makes
it more difficult for the heat in the head to get out.  Then, when you raise
the rpm up really high (over 5000) the water pump speeds up circulation very
fast.  This transfers a lot of hot coolant out of the engine and into the
radiator.
On my car I have rodded the rad twice, and done EVERY other thing to reduce
the running temperature.  If every other component is operating at 100% in the
cooling system the only other thing that could increase the amount of heat
transferred from engine to ambient is to increase the flow rate through the
radiator. 
I guess what I'm suggesting is that maybe the V12 runs at such low rpm when
driven softly that the water pump circulation rate is borderline when it's 100
degrees outside?
It reminds me of something Kirby said a long time ago about trying to improve
the impeller design of the water pump to increase coolant flow at full open
thermostat condition.
Maybe we could figure a way to put a SMALLER pulley on the stock water pump to
increase flow at all rpms?(....I like that, it sounds simpler than any other
proposed fix).
Another way to test this would be to deliberately drive the car holding it in
first and second gear through higher revs and see if the temperature gauge
drops.

Julian Mullaney



In a message dated 98-07-25 09:14:50 EDT, jcortney@bizcenters.com writes:

<< ....big snip....... Shut the car down ........ restart the car the temp
guage reads just a hair over the "N".  Back into traffic I go ......needle
stays exactly where it was, just above the "N".  ...........drive on sparsly
traveled roads at
 about a constant 30 - 40 mph and there is no change in the temp guage. 
 Still above the "N".  
 Now this is LIGHT YEARS better than it was before all the repairs (half way
 between the "N" and "H" but still not what everyone else is reporting.>>

---

• Prev by Date: FW: [xj-s] The ubuiquitous overheating problem
• Next by Date: [xj-s] need advice....QUICK
• Prev by thread: Fw: [xj-s] Still Looking to buy
• Next by thread: [xj-s] need advice....QUICK
• Index(es):
  • Main
  • Thread