'85 4kq - overheating - clogged radiator?

[Ben Swann]

Thanks for the reply Tony.

I took the radiator out.  It did not appear clogged or have noticable
debris.  I reverse flushed and flushed form differents points with garden
hose.  The radiator almost looks to good to be the original.

I was going to swap with another I had, but plastic end cap cracked when I
was removing from parts car due to stupidity and frustration on my part.

So, I slapped the old one which has metal end caps back in.  I ran some
wires to switch the fan on if it starts heating up again.  The problem
mainly happens when idleing for a long time.

I am still puzzled at why it seems to get very hot up top, to the point
that it was spewing out of the overflow, yet the bottom does not get hot
enough to turn the fan switch on.

Ben

On Tuesday, October 08, 2002 3:00 PM, Tony Lum [SMTP:tlum at flash.net] wrote:
>
>
> At 10:24 AM 10/8/02 , you wrote:
>
> >I have been troubleshooting an overheating problem in the '85 4kq -
> >formerly rally car now being pressed into service as my daily
> >driver/beater.  The fan switch circuitry works OK as tested from the
switch
> >at the bottom of the radiator.  I replaced the thermostat, thinking that
it
> >was not opening - the one I removed was definately not opening all the
way.
> >   I still had the problem.  Car heats up at idle to the point where
> >pressure forces coolant out the overflow cap.  Replaced cap.    I just
> >installed a new thermo-switch.  It seems that the top half of the
radiator
> >is getting very hot, but the bottom half is only warm - not enough to
heat
> >the fan switch(also cool).
> >
> >Is it possible the radiator is so clogged that there is no circulation
> >getting to the bottom?  What else can be wrong.
> >
> >BTW I also flushed the system when I replaced the thermostat.  As a side
> >note, if I run the heater and vent fan on high, I can keep the car from
> >overheating (that was after I cleaned the mouse nest out of the squirrel
> >cage - another saga).
> >
> >Ben
>
> Yes, that can happen.  Luckily I caught mine early enough (it was
starting
> to run hot even at freeway speeds).  When I removed the radiator, I could
> see it was clogged with sediment and white particulates at the
> bottom.  Luckily I ran into a CGT at the wrecking yards with a recently
> re-built radiator.  Slapped it in and temps immediately dropped below
> half.  I could even go back to the stock thermostat rather than the 80
deg.
> I had installed, but it runs great and I've got more important problems
to
> solve.  Be sure your head gasket isn't leaking just in case.
>
> HTH,
>
> --
> Tony
> _______________________________________________________________________
>
> Tony Lum                                  1987 5000CS Turbo Quattro
> Berkeley, California, U.S.A.                1985 4000CS Quattro
> Audi Owner/Driver/Mechanic by Necessity ;^)   1980 5000S Sedan
>                                                 1987.5 Coupe GT
>                                                  1983 Ur-quattro
> _______________________________________________________________________
>