'85 4kq - overheating - clogged radiator?

[Joshua Van Tol]

It probably is clogged with corrosion. Did you have a radiator shop
remove the tanks and check? It's not usually that expensive to have a
radiator "rodded out" which entails removing the tanks, and running a
rod through each coolant passage to remove the gunk. Brass and copper
radiators are horrible about corroding, much more so than aluminum
ones. It's a good thing they are repairable, because you've got to do
it much more often.
On Tuesday, October 8, 2002, at 04:18  PM, Ben Swann wrote:

> 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
>> ______________________________________________________________________
>> _
>>
>