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corrosion in coolant systems

	Discussions about failed o-rings in M3 motors has forced
me to admit my sin.
	I allowed the coolant to get old and yucchy in my '83 528e.
Further, what I thought was a coolant leak in the radiator turned
out to be a leak in the hose from the expansion tank to the radiator.
The rubber had gotten old and brittle, whereby the hose clamp lost
it's effective grip on the hose - presty, pinhole leak.
	But back to the coolant saga.  I started to loose effective
cooling & suddenly lost the heating power of my heater.  Now, normally,
a heater fails full on (fun in the summer), but the heater valve can
be rebuilt for about $30.00.  In my case, I assumed that since engine
over heats & no heat == no water pump.  The belts were good, so it's 
spinning.  Hmm, open exansion tank cap.  Holding pressure, but
whats all this brown foam.  Now, you experts will say, aha, oil in
water==cracked head.  Nope, but it was two year old anti-freeze.
So, I pulled the thermostat out (and tested it - o.k.), and flushed
the system.  And flushed. And flushed.  Put a can of super flush
in, and flushed. Pulled various hoses at thermostat and back
flushed.  All the while, evil foul looking junk came out. 
Then decided to pull the water pump, due to what felt like
a bearing going (at least 70K on pump - looked original when yanked).
Replaced waterpump and back flushed some more.
	Replaced anti-freeze and coolant.  Still runs hotter than
it should, but 15-20 degrees cooler than before.  Coolant is still
a nice green color, and there is no brown foam in the expansion tank.
I suspect that with a 150K miles, and my two years of neglect,
the radiator is clogged to some extent.  Yanking the heater valve
showed the filter screen to be clogged (therefore, no heat), 
I've temporarily replaced the valve with a C shaped piece of copper
tubing, I'll replace it in the spring.  The radiator is unrepairable
by the local radiator shop - they can't get the side tanks to fix
it :(

Moral:  Replace your coolant every year with distilled water and
the proper anti-freeze.  Also, when you remove the old stuff,
it doesn't hurt to flush out the entire system (not just the
radiator).  

Larry


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 "When you are occupying a position which the enemy threatens to surround,
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                                        Napoleon I
Lawrence C. Schuette			  [email protected]
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Naval Research Laboratory		  (202)445-0648 (cell. phone) 	
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