in-depth radiator theory (attn cheapass ron, brian mcgarvey, list, radiator gurus)

["Allyn" <amalventano1@home.com>]

ok, guys, i have some theories on our (well, some of our) radiator delemas.
    i've been checking out the radiator/hose layout on my car. the coolant seems to come into the
top, go across the top half of the radiator, down the other side, and across the bottom half and out
to the thermostat. Where the temp fan switch comes in is at the 1/2 way point. Now comes the theory.
Some other location info: oil temp comes right off the filter. water temp comes right off the head.
Now, why would our cars run over 100 on the oil temp and over 3/4 the way up on the water temp?
    I believe a crapped up radiator can cause this while still giving 'normal' fan cycles and the
like. Imagine said radiator is all crapped up, therefore has low flow. Hot water from block goes
into radiator (slowly). Slowly makes its way to the temp switch. Eventially trips the sucker, but
due to the low flow, the fan doesnt stay on for very long due to the low flow condition (water gets
cooled off much more since its moving slower, spends more time by the fan, etc...). On top of the
typical observation that this is a bad thing, whats also worth noting is this is feeding 'batches'
of cold water into the engine. The ideal way the system should work is temp goes up, fan kicks on
for a while to drive temp down (observable on gauges), fan kicks off, all is happy. What im getting
is temp goes up slowly as fan cycles on and off. temp eventually stabilizes at 115c oil and 3/4
water (at night, in SC). Now I know alot of you want to jump on the "check grounds/gauges" thing.
All grounds are good. Resistance measurements taken directly at rtd's (temp senders) on engine
indicate that the water around the senders is in fact at these higher than normal temperatures.
    Brian McGarvey could easily spout out about 3000 formulas to relate water speed through a heat
exchanger to differential temperature across said heat exchanger. Clog up radiater - higher
delta-temp - water out of radiator is cooler, while water into it is hotter - fan switch is 'fooled'
by said condition - engine runs hot as freggin hell. okok, Q=mc(delta)t. Q is overall heat transfer,
m = mass flow rate (water speed), c = heat transfer coefficient (constant, unless you change
antifreeze concentration), and delta t is the diff between inlet/outlet temp. drop the m, and the
delta goes flying up even if the radiator is removing the same amount of heat. Happy there, brian
:P.
    Another important thing is that when i pulled the water temp fan switch off of the radiator
there was a 1/16 to 1/8" layer of black goo on it. This was in a big passage! imagine whats in every
single tube on the radiator!
What this tells me is that the prestone flush, while getting alot of rust and stuff out of the
system, didnt touch the deposits of crap in the radiator.
    Now for the burning question: There has to be some chemical i can put in the radiator overnight
(radiator off the car) that will break this stuff down. i figure i can flush it alot better off of
the car (powerflush with hose, really hot water, etc). What are you guys thoughts on using stuff
like CLR (that calcium lime rust breakdown thingy from tv), or perhaps diluted engine cleaner or
carb/choke cleaner. That stuff works wonders on the outside, i would imagine it could do something
for a radiator.
    I would much rather spend 5-10$ on cleaning it than $150ish on a new one.
OK, im off to yank crapped up radiator.
al

Allyn Malventano, ET1(SS), USN
87 rocco 16v (rieger gto - green - 'der rocco' - restoration in progress, need stub axle, wobble
wobble)
87 jetta 8v wolfsburg 2dr (260k, still tight :)



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