Driving Without A Thermostat

On Mon, 14 Feb 2005, Billy Bad Assr=A9 wrote:

> > So, @ a higher RPM, the water pump pressure would overcome the
> > radiator cap's rating and force coolant out
>
> Bzzt! There is no "water pump pressure". The water pump does not
> generate pressure. Pressure in the cooling system is created by
> thermally-induced expansion.
>
> Bah >> pressure, meaning the Flowing side!!!!

Pressure means pressure. Flow means flow. The two are not synonymous.

> if I increase the rpms -- what do you suppose the water pump will do???!
> the Flow will be increased!

Indeed. And the pressure will change not at all.

On Mon, 14 Feb 2005 22:38:23 -0500, "Daniel J. Stern"
> wrote:

>On Mon, 14 Feb 2005, Billy Bad Assr?wrote:
>
>> > So, @ a higher RPM, the water pump pressure would overcome the
>> > radiator cap's rating and force coolant out
>>
>> Bzzt! There is no "water pump pressure". The water pump does not
>> generate pressure. Pressure in the cooling system is created by
>> thermally-induced expansion.
>>
>> Bah >> pressure, meaning the Flowing side!!!!
>
>Pressure means pressure. Flow means flow. The two are not synonymous.
>
>> if I increase the rpms -- what do you suppose the water pump will do???!
>> the Flow will be increased!
>
>Indeed. And the pressure will change not at all.

Only in a theoretical "unrestricted system."
But that isn't the way it works in a car. There are plenty of places
of restriction, and "free flow" isn't encouraged so a PUMP is put
there to help the water to flow at a desired rate.

Assumption being that the faster the engine is running, the faster the
pump needs to be moving water through it to remove the excess heat.

There definitely is a FORCE applied by the impeller of this pump,
otherwise the water wouldn't move anywhere, it would just stay where
it is. Maybe this FORCE is what BBA is referring to when he talks
about "increasing pressure," although it should be noted that water is
not compressible, it does distribute increased force in pounds/inch
squared. Just look at how a submarine has to keep itself above *crush
depth* lest it becomes another artifact on the ocean floor.

This pressure does increase, and that is what the impeller does, it
increases pressure on the output side relative to the input side and
this helps move the water along through the circuit. If you put a
gauge both before and after the centrifugal pump, you will indeed see
a force/pressure differential. But this force/pressure differential
stays close to the pump inlet and outlet, and disperses rapidly,
geometrically as you move away from the pump in either direction.

Lg

Pressure does indeed vary within the cooling system. In race systems, we
often run a bleed from the top of the rad to the header tank. Since the
header tank is usually at the output of the head it sees the highest temp
and pressure, and we have seen that air can actually be forced from the
header tank into the rad rather than the other way around. In that case,
you need to bleed the system cold and seal it off. A good way around this
is to run the bleed from the rad top to the intake of the water pump.
That's the lowest pressure point in the system ( albeit not by a lot) and
the air is bled off and goes to the header tank naturally. Seems somewhat
wrong, but it works.

Brian


"Daniel J. Stern" > wrote in message
.umich.edu...
On Mon, 14 Feb 2005, Billy Bad Assr wrote:

> > So, @ a higher RPM, the water pump pressure would overcome the
> > radiator cap's rating and force coolant out
>
> Bzzt! There is no "water pump pressure". The water pump does not
> generate pressure. Pressure in the cooling system is created by
> thermally-induced expansion.
>
> Bah >> pressure, meaning the Flowing side!!!!

Pressure means pressure. Flow means flow. The two are not synonymous.

> if I increase the rpms -- what do you suppose the water pump will do???!
> the Flow will be increased!

Indeed. And the pressure will change not at all.

Brian wrote:
>
> As a last resort, run a thermostat. Big benefit: you can force the engine
> to warm up to at least the temp of the thermostat. Big drawback - they have
> failed in such a way as to stick closed. Guaranteed overheat when that
> happens. I had one engine/car combination that I had to run a thermostat
> in, even taping the rad right off wouldn't warm this thing up. It never
> failed, either. I always made a point of watching for it to operate,
> though, you could tell by the temp gauge exactly when it opened.
>

I plan on keeping the tstat in this year.
New high flow water pump, new aluminum rad (instead of junkyard stuff)
will keep it cool. New race carb without a choke means it can't run too
cool. What I've done is take the stat and drill 3 or 4 1/8" holes in
the edge so even if it fails it's not totally closed. I call it my 150
degree stat.

Ray

On Tue, 15 Feb 2005, Brian wrote:

> Pressure does indeed vary within the cooling system. In race systems,

....Race systems are in race cars. The OP's query concerned street cars.

OK, the pressure varies within street systems too. You cannot have flow
without a pressure variance. If the pressure was static, there would be no
flow.

Brian


"Daniel J. Stern" > wrote in message
n.umich.edu...
> On Tue, 15 Feb 2005, Brian wrote:
>
>> Pressure does indeed vary within the cooling system. In race systems,
>
> ...Race systems are in race cars. The OP's query concerned street cars.
>

Ray, if you want you can put the temp gauge downstream of the T'stat. That
gives you a totally positive indication that the t'stat is working. You can
also go up to say 1/4" holes in the t'stat plate. If you have a high-flow
pump you can experiment with slowing it down more with a pulley change.
Adding more expansion tank, either with a separate tank or with a tower on
top of the t'stat housing on the head, works well too - some systems like
more air in the header. Lots of ways to skin the cat, lots of things work
well.

If you're running dirt, then having the t'stat will force the engine up to
temp and give you a lot of headroom if the rad starts to get blocked. My
buddy was crewing on a Daytona Prototype at the 24 hour race last weekend
and they saw temps go to about 260 due to crud in the rad. Changed the rad
out and temps went right back to 180. Having "extra" cooling is a good way
to go sometimes.

Brian


"ray" > wrote in message
...
> Brian wrote:
>>
>> As a last resort, run a thermostat. Big benefit: you can force the
>> engine to warm up to at least the temp of the thermostat. Big drawback -
>> they have failed in such a way as to stick closed. Guaranteed overheat
>> when that happens. I had one engine/car combination that I had to run a
>> thermostat in, even taping the rad right off wouldn't warm this thing up.
>> It never failed, either. I always made a point of watching for it to
>> operate, though, you could tell by the temp gauge exactly when it opened.
>>
>
> I plan on keeping the tstat in this year.
> New high flow water pump, new aluminum rad (instead of junkyard stuff)
> will keep it cool. New race carb without a choke means it can't run too
> cool. What I've done is take the stat and drill 3 or 4 1/8" holes in the
> edge so even if it fails it's not totally closed. I call it my 150 degree
> stat.
>
> Ray

On Tue, 15 Feb 2005 13:34:04 -0500, "Brian" >
wrote:

>OK, the pressure varies within street systems too. You cannot have flow
>without a pressure variance. If the pressure was static, there would be no
>flow.
>
>Brian

correct

>
>"Daniel J. Stern" > wrote in message
in.umich.edu...
>> On Tue, 15 Feb 2005, Brian wrote:
>>
>>> Pressure does indeed vary within the cooling system. In race systems,
>>
>> ...Race systems are in race cars. The OP's query concerned street cars.
>>
>

Daniel J. Stern wrote:

> On Mon, 14 Feb 2005, Billy Bad Assr� wrote:
>
>
>>Once upon a time in the early '60's, most passenger vehicles used a
>>low-pressure type of a radiator cap.
>
>
> Early '50s, yes. Early '60s, no. By the early '60s, 14psi to 16psi caps
> were the most common.
>
>
>>So, @ a higher RPM, the water pump pressure would
>>overcome the radiator cap's rating and force coolant out
>
>
> Bzzt! There is no "water pump pressure". The water pump does not generate
> pressure. Pressure in the cooling system is created by thermally-induced
> expansion.
>

Not entirely true. Since the radiator is somewhat restrictive, the water
pump tends to increase pressure in the 'hot' tank, and decrease pressure
in the 'cool' tank. Thats the whole reason that lower radiator hoses
have springs inside them- to keep the waterpump-induced differential
pressure from collapsing the lower hose and blocking flow. Of course
once the system comes up to normal working pressure (induced thermally,
as you state) then the waterpump would have a heck of a hard time
overcoming the static pressure and collapsing the hose. But at 6500+
RPM, it CAN happen.

"Daniel J. Stern" > writes:
> On Mon, 14 Feb 2005, Billy Bad Assr© wrote:
>
>> > So, @ a higher RPM, the water pump pressure would overcome the
>> > radiator cap's rating and force coolant out
>>
>> Bzzt! There is no "water pump pressure". The water pump does not
>> generate pressure. Pressure in the cooling system is created by
>> thermally-induced expansion.
>>
>> Bah >> pressure, meaning the Flowing side!!!!
>
> Pressure means pressure. Flow means flow. The two are not synonymous.

But they are not unrelated either. To get flow in a closed system
(like a cooling system) you need to have a pressure differential. This
is very simple fluid mechanics.

--
Ignasi.
(using SPAM trap e-mail address)