Re: Not this again

[Glenn Merrell <gmerrel@domain.elided>]

Hello Kim,
    Ah, gee wiz, the search for those simple answers.
TEMPERATURE's RISING:
    If the temperature is slowly creeping up at road speed, then the heat is not
being transferred from the coolant to the radiator to the air.  At Road Speed
above 20 MPH +, the fan is of no use.  This rise in coolant temperature could be
many reasons: (1) the radiator core is not the correct match for your engine and
is not allowing either water to pass at a rate to allow heat to exchange, i.e. too
fast, or it is too thick or air restricted to allow air to pass properly through
the radiator to take the heat away; (2) the coolant going into the radiator is
very hot or not flowing properly through the radiator.   Forget the fan, clutch
and cowling, they have no effect at 70 MPH, unless the fan is not rotating at all
and is an obstruction, which is unlikely.  Since it is not cooling properly at
road speed, adding an electric fan will most likely be of no consequence  to aided
cooling.  Probable source of problem then is the radiator.  What is the core
configuration of your radiator?  What happens if you open the cockpit heater valve
full open while driving at 70 mph, does the temperature stabilize?  Again, points
to radiator heat transfer.  Try running with a coolant mix of 25% antifreeze and
75% water.  If your temperature stabilizes, you have a heat transfer problem.
Remember, the thermostat has one, and only one function; that being to maintain a
MINIMUM engine temperature.  MAXIMUM temperature is regulated by the heat being
exchanged by the radiator.  Where is your analog temperature gauge sensor mounted?

   The Rebuild:
    This engine was rebuilt for a reason, was it overheating and blown gaskets?
If so, what was the cause?  Stag engines have a tendency to accumulate the solids
from the coolant system around the base of the cylinder walls where casting sand
may have been left.  Unless you specifically pointed out these areas out to the
engine builder, a normal acid bath may not have removed any of  the sediment
accumulated there.  Sometimes it needs to be scrapped out with a rod.  With no
coolant accessing these spots, they superheat and cause flash boiling.  A second
area to pay attention to is the suction side of the water pump.  Water flows down
through the heads into the engine block past the cylinder walls toward the water
pump.  Sometimes cast iron flashing gets stuck at or in  the entrance to the water
pump restricting flow.  Are you sure that the thermostat has a bypass disk on the
back?  Checking the routing of the water hoses is not a bad idea either.  Did you
blow out the water passages in the intake manifold with high pressure air before
mounting?  Did you use silicone sealant on the intake manifold gaskets that may be
blocking the flow between the manifold and cylinder head?  I'd also check the
coolant passages at the intake manifold entering the cylinder head for
obstructions.
Not a lot of good advice if you are trying to get to the VTR National Convention
next week.  sorry!
Regards,
Glenn Merrell
"Keep Your Stag Cool, Install a NEW Composite Cowl Today"

See it at the site below:
http://pw1.netcom.com/~gmerrel/stagcowl001.html

Triumph Stag Registry USA VP
membership inquiry's to:
Mike Wattam <101714.1343@domain.elided>


Ehlem@domain.elided wrote:

> Fellow Stag owners,
>
> I know you've responded to a zillion or more questions about overheating, but
> I've just got to ask again.
>
> The Situation:
>
> Complete rebuild on the engine. .20 over pistons installed. Everything is new:
> hoses, water pump (six vane), etc. The valves line up dead on with #2 cylinder
> at TDC. The radiator has been recored. The original fan shroud is in place.
> The viscuous fan new and replaced (courtesy of Walter Holliday, Stag
> Specialists). The coolant fresh. Filled with the heater in the hot position
> and the front of the car jacked up to aid in the escape of air pockets. The
> engine now has 3,000 miles on it. By in large it runs well with a troublesome
> low end stumble that is more annoying than debillitating (sp?).
> But it won't cool down!

> 1. Is there a cavitation occuring over the water pump?
> 2. Does the 6 vane water pump simply not circulate enough water to cool down
> the temperature?
> 3. Is it possible that I have incorrectly routed heater hoses? (okay, I'm
> grasping here)
> 4. Is it because I have a BW35 and at 65 mph the engine and tranny have to
> work too hard (33-35 on the tach) therefore creating excessive heat. (I doubt
> this given that the problem will occur at lower speeds in high (90+) heat.
>
> Tell me it's something simple that my less than agile mind didn't think of.