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Re: Technical Comments on Cooling

To: mgs@autox.team.net, MG1935@aol.com
Subject: Re: Technical Comments on Cooling
From: "Ramm, Andy" <ARAMM@sv.tbgi.com>
Date: Mon, 26 Jun 1995 17:22:13 -0400
Also, if you don't go to the trouble of installing an electric fan, be 
sure you at least upgrade the old four-vane steel fan on older LBCs to a 
new six-vane plastic one.  They're much quieter, pull tons more air 
through the rad and are a fraction of the total weight of the steel fan, 
putting less stress on the H20 pump.  They're also flexible, and if 
godferbid the screws came out, it probably wouldn't puncture the rad 
either.



While I'm at it, is there a recommended method of cleaning the OUTSIDE of 
the radiator?  I usually use a hose and brush, but let me know if there's 
something special I should do.



Cheers,



Andy



----------------Original Message Follows----------------

The following is an article by Art Ziesk which ran in the Texas Chapter 
News,

the newsletter of the Texas MG Register.



Mark Dement

'35 PA

'59 MGA



With summer once again near, many people will experience cooling system

problems and overheating to various degrees. It seems that very little

helpful information is available on cooling 

systems and frequently most mechanics are baffled as well as the 
frustrated

car owners. I will try to briefly cover most of the important 
considerations

governing automotive cooling, which hopefully will clarify everyone's

understanding of this important subject.



Dallas summer's high temperatures make it necessary to have our cars 
cooling

system operating near 100% efficiency since many cars were designed for

maximum temperatures less than we experience. Operating under stabilized

conditions with a fully open thermostat (i.e. 60 MPH on the highway) it 
can

be shown that the engine temperature will rise very nearly degree for 
degree

with the ambient air temperature. Thus a car running 190o at 80o will

increase to 220oF at 110o air temperature. This may be surprising to many 
of

you, but is a normal characteristic.  A

fully opened thermostat occurs when the ambient temperature is no longer 
low

enough to allow the thermostat to maintain the temperature at it's rating

(usually 160 or 180oF) and the radiator's heat transfer ability controls

temperature.



The thermostat's purpose is mainly to maintain an operating temperature 
at

the 160o or 180o rating when ambient temperatures are low, so the engine 
will

operate more efficiently and the heater can produce hot air. A common

misconception is that removing the thermostat or using a lower rated

thermostat will allow a car which runs too hot to run cooler; this is not

true and it is unwise to run without a thermostat as many engines are

designed to have an internal passage blocked by an open thermostat which

significantly increases cooling flow to the radiator. The most common 
failure

with thermostats is sticking partly open causing engine (and heater)

temperatures to be too low.  Less often a thermostat will stick closed

causing very rapid boilover.  Since the thermostat is very cheap, if 
there is

any doubt as to it's condition, it is recommended it be replaced and the

results observed.



The first step in optimizing cooling system performance is to be certain 
the

engine performs at it's best. A thorough tune up should pay particular

attention to being sure that ignition timing is correct not only 
initially,

but at all speed and load conditions. Many older British cars will have 
the

mechanical advance stuck and inoperative and/or the vacuum advance 
diaphragm

ruptured.  Retarded ignition timing will cause sluggish performance with

overheating even if the cooling system is in top condition. The vacuum

advance is mainly intended to increase part throttle fuel economy, but if

inoperative will cause higher operating temperatures; make sure it works

properly. An inoperative mechanical advance will cause very noticeable

performance loss. 



Many cars will still have cooling problems even when the thermostat and

tuning are in top condition. A physical characteristic of the automobile

engine is that it produces heat, increasing in magnitude with increasing

speed and load, which must be removed by the cooling system, The heat

produced by the engine is transferred to the coolant which is circulated 
to

the radiator by the water pump. This heat is then transferred by the 
radiator

to the surrounding air, the coolant re-circulated  and the process 
continued.

Since the coolant is continuously re-circulated it is important that none 
is

lost through leakage. 

Coolant leakage is the most common cause of overheating and often is 
simple

to correct. Replace any questionable hoses and make sure all clamps are

tight. A noticeable water leak that                                    

is hard to find usually turns out to be a water pump seal.  Although 
water

pump seal and bearing failures are common, the water pump rarely is the 
cause

of overheating and replacement is unwise if the bearing and seal are OK.  
An

exception to this is the occasional disintigration of plastic impellers.



When no water leakage can be found and water loss is still a problem the

water is likely being lost through the overflow (or out the 
tailpipe/blown

head gasket or worse). Since most modern cars are dependent on a high

pressure system often a bad radiator cap will cause water loss; if any 
doubt

replace the cap. Head gasket leakage usually worsens rapidly soon 
becoming

intolerable.  If suspected, combustion leakage can be detected by filling 
the

radiator or tank to the very top and starting the engine while observing 
the

coolant.  If water gushes out as soon as the engine is started or if  
steady

gas bubbles are evident major engine work is  indicated. 

Combustion gas detectors are available, but usually only verify the 
obvious.



At this point, if everything covered was put in order, some cars will 
still

display an overheating problem. Before going further with any solutions 
it is

important that "overheating" be defined more clearly. Some may disagree, 
but

my definition of "overheating" as when temperature rises to a point when

boiling occurs, coolant is lost from the overflow, and a stabilized 
condition

cannot be maintained.  Thus the "overheating" or boiling temperature 
varies

significantly with combined effects of altitude, coolant solution, and 
system

pressure.  With a 14# pressure system, 50-50 coolant water mix, and at 
sea

level, the boiling point will increase from 212o F to 265o F.  Most 
modern

cars can operate safely at considerably higher temperatures than older 
cars

which have non pressure or low pressure cooling systems. Addition of a 
50-50

coolant water mix with no pressure will raise the boiling point to 226oF,

thus giving a slight margin over the traditional 212oF danger point.  
Never

use over 50% coolant for summertime as the heat transfer ability is 
seriously

reduced causing higher metal temperatures and accelerated engine wear.



Finally we will discuss the major variables in the cooling system; the

radiator and fan combination.  The radiator is selected by the 
manufacturer

to provide adequate cooling under most normally encountered situations, 
yet

is not over designed so as to cost more than necessary. Usually the 
standard

radiator is inadequate in extreme climates or under severe operating

conditions and most manufacturers offer an increased, or heavy duty 
cooling

package. The fans purpose is to provide adequate air flow through the

radiator when stopped or traveling at low speed and has no significant 
effect

at speeds over approx. 30 MPH. A significant point to remember is that a

larger fan, electric fan, or fan shroud will not improve an inadequate

radiator's performance at road speeds.  



Radiator problems are best detected by driving the car at steady highway

speeds and observing the stabilized operating temperature. If the 
operating

temperature is too high and increases with increases in speed and load, 
the

radiator is not  adequately removing heat. If a radiator problem is 
indicated

the only solution is to remove it and send it to a reputable radiator 
shop

for cleaning. Fast flush and chemicals to clean a radiator in the car are 
at

best only partially effective and  usually a waste of time. The radiator 
shop

actually unsolders the top tank of the radiator and physically cleans 
each

tube so the radiator will  operate near 100% efficiency when cleaned

properly. The improvement in cooling after properly cleaning a radiator 
is

often dramatic. Radiator cleaning should always be done when an engine is

overhauled.  



An inadequate fan is easily detectable when a car runs excessively hot in

slow traffic or at idle; but cools to a normal operating temperature soon

after reaching steady road speed.  Often modern cars are equipped with a 
fan

clutch intended to reduce power drain from the fan at road speed. A 
defective

fan clutch often is the cause of overheating in slow traffic.  Missing or

broken fan shrouds often cause some air to circulate without passing 
through

the radiator. Electric fans have become increasingly popular recently and

work very well. Often the addition of an auxiliary electric fan is the 
beat

way to improve low speed cooling as well as improve air conditioner

performance if so equipped.  



I have tried to describe as many important facets of cooling system 
design

and performance as possible in a brief summary.  One of the most 
important

things to consider is to define what

is normal for the particular automobile you are dealing with, and if 
normal

performance will be adequate for the use the automobile will be subjected 
to.

If improved cooling performance is desired, non standard components must 
be

selected carefully to give the desired results. Most cooling problems are

very straightforward, but occasionally very weird or unusual situations 
are

encountered. A thorough understanding of the basic operating principles 
is

necessary to resolve cooling problems as well as any mechanical problem.



Art Ziesk









     

---------------- End of Original Message -----------------




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