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Re: Overheating 4kq

Tony Lum is right about the load to the oil temp gauge:
it is not regulated - the indicator shoots up if you push
in the cigarret lighter.

However, my car running at temps which exceed the ones that
fried that scirocco really freaked me out, so I set out
to examine and clean the cooling system last sunday. 
Already from the Vegas experience I had noticed that the
coolant was quite cloudy which in turn made me conclude 
that the radiator shop which had resoldered the tank seams of my car's Audi original metal radiator a year before 
had installed the wrong kind of antifreeze with the darned 
phosphates in it. I really should not have trusted them 
with that since they brutalized my car in their attempt
to remove and reinstall the radiator. After I left the shop
I noticed that bolts and washers were liying in various
places under the hood. Sure enough, last sunday I saw
white hard mineral deposits wherever I could peek inside
hoses, pipes, and the radiator. These deposits were thick,
more than thick enough to completely clog those narrow
passages that the coolant circulates through in the 
radiator. In fact the slits that can be seen from the hose
inlets appeared narrowed and clogged before my day-long
radiator-cleaning ordeal. 

Although I worked all sunday, my ordeal seems to have not
worked well enough. First I flushed and back flushed the
entire cooling system and then the motor, heater, and 
radiator individually with a garden hose with good 
pressure. Then I used the heavy duty powdered radiator
cleaner by Prestone in the 2-in-1 can one side of which
contains oxalic acid (very strong, fatal poison) and the
other, a neutralizer - sodium bicarbonate. Following the
instructions on the can, I refilled the system with water,
then ran the motor, then waited for it to cool down, then
added the acid cleaner and water to fill up, then ran it
for an hour @ 1200 rpm, then for good measure I flushed
everything again as first described with the garden hose
after the hours it took for the car to cool down, then 
added the neutralizer, then ran it for 10 min during which
some acid-base reaction occurs generating huge amounts of
CO2 with immense pressure in the cooling system. Afraid of
blowing my head gasket seal, I opened the pressure cap to 
have a volcano of foam and bubbles erupt from the coolant
tank and the coolant temp needle shoot up. I suspect this
same pressure finished off the already weakened head 
gasket in my friend's scirocco whose terminal overheating 
we had tried to correct with this cleaning procedure wich
eliminated the overheating and left its aluminum radiator
squeaky clean... but too late. With this in mind I turned 
off the motor immediately, and waited hours again for its 
cool down. Finally, I flushed everything again producing
an amazing amount of white debris in the rinse water, but
on inspection the inside of the radiator still looked caked
with somewhat thinner white deposits and still possibly
clogged - not at all like the shiny aluminum of the 
scirocco's radiator. When the rinse water came out clean,
I installed the new Prestone long-life coolant that claims
to be phosphate and silicate free - can a Prestone coolant
really be safe for our Audis?? when I started the car to
test it I became terrified to see drops of water comming
out of the tailpipes since that had been the first symptom 
of doom for the scirocco; however, unlike the scirocco, as
the car warmed up they dried up and no white smoke came
out, ever, of the exhaust - and the motor ran fine. The
moisture was probably part of hurricane Linda's gift of
opressive humidity to San Diego :) Thus the 4ksq runs 
really fine, except that now the coolant temp gauge gets to
the 2nd mark from the hottest when thecar idles (only then 
the fan kicks in) and the oil temp gets up around 130 
degrees celsius when cruising at 65-75 mi/h while the 
coolant temp needle goes below 1/2. From the responses 
that I have gotten to this thread, I'm beginning to realize
that this is all pretty normal behavior for the 4kq. 

However, the change to somewhat warmer indicators might
mean something, perhaps that better circulation of the
coolant allows it to pick up more heat from the engine than
before, and now other defects in the system such as the 
water pump, thermostat and ancient radiator show up more. 
Therfore, at my first economic oportunity, I will replace
the water pump with the way-over-the-hill timing belt, the
aftermarket (though German) 'stat that I got during the
Vegas emergency, and the atherosclerotic radiator. Can 
anyone tell me what the best radiator available for the 
4ksq is and where I can get it at the best price?

Also, I will change back to Amsoil 2000 0w30 unless someone
can convince me that the 20w50 offers better protection
even though it appears to make the motor run 20 deg C 
hotter (although the higher oil temp reading may be due to
the thicker oil having better heat transfer ability in
which case I may be wrong - am I?).

As far as the cleaning ordeal went I would recommend 
against it. First, the pressure from the CO2 generated by
the neutralization reaction was powerful enough to destroy 
gasket seals and might very well have done so to my
friend's sirocco; thus, this Prestone cleaner may 
cause serious damage to your engines. More importantly,
during the procedure I got doused every time by the gush
coming out of the radiator. It was scary enough to bathe
in ehtylene glycol with all the assorted poisons picked up
from the circulation path - including lead bloom from the
stupid solder that the %@#!^*! radiator shop used. To then
take a shower of acid that warns to be "harmful or fatal if
swallowed" and to "cause eye injury", together with some 
nice lead oxalate picked up from said solder is sheer 
foolhardiness. Yes, I got a lot of this in my mouth, too.
After this unpleasantness, I will simply get a new radiator
and maintain the cooling system religiously with the
proper phosphate-free coolant and deionized water mix. 
i have learned the hard way how essential is to follow the
instructions of the manufacturer and the Bentley factory 
manual. Then the deposits won't form again, and milder
cleaners such as the non-acidic Prestone radiator super 
cleaner should suffice, and I will have protected my Audi,
myself and the environment. By the way, is Sierra coolant
good for Audis?

I thank you beforehand for answering my questions, and hopethat I have answered some of yours.

Luis Patino 

1985 4ksq - best car I've ever had