4kq overheating - still

[Bernard Littau]

Hi Ben,

If all the hoses and passages you can inspect are fine, and the radiator is
not clogged, then it must be something else.

The heater putting out marginal heat means you do not have good flow (duh!
:-) through the heater core.  I would pull apart the water pump and take a
look.  I've had a water pump separate the impeller from the shaft on a non
Audi, so this might be a possibility.  You may also have a clog in one of
the passages to/from the pump chamber.

Other things you might do:

Install a clear plastic tube in line with the heater hose and see what kind
of flow you see through the tube.  Not sure what this will tell you, but it
might provide a clue.  I would expect to see flow as bubbles and crud move
through the clear tube.

Install one of those flush and fill kits with the in line tee in the heater
hose that you can hook up a garden hose to.  Do a flush, but resist pushing
too much flow through the garden hose as you can blow things apart (cooling
system normally max at 15 psi, garden hose easily gets to 60 psi).  Many of
the better flush kits have a flow resistor of some sort for this reason.

Best,

Bernard Littau
Woodinville, WA



>
> I have been at this overheating problem in a '85 4kq for too long and
> this problem perplexes me.  I am beginning to think the problem maybe
> internal to the engine.
>
> So far I have tried 3 different radiators - the last from a known
> running 4kq which kept guage near center except on very hot days with
> AC.  Still it overheats - not so drastically now, but after 15 min
> driving, the guage will begin to peak and the car will vaporlock and
> not restart if I shut down.  Head seems to be getting unusually hot.
>
> The top of the rad. gets warm/hot, but the bottom remains cold enough
> to condense moisture.  The lower rad hose gets hot near the water pump
> outlet on the engine and gets progressively cooler toward the bottom
> where it enters the radiator.  That same hose seems very pressurized
> when hot, as does the upper hose which goes to the cooling neck.
>
> The heater blows warm, but not as hot as I would expect - Hmmm.
>
> So far I have tried new thermostat and just have been running without
> one 'til problem resolved - it definately is better without t'stat, but
> that is not the problem.
>
> Both main hoses as well as overflow tank hoses are free and clear.
> Engine takes water from upper hose and expels out the lower hose when a
> garden hose is fed in and vice versa.  I have not seen any kind of
> obvious suction when hoses were put in tank of water with engine
> running, probably water pump lost prime as it is hard to duplicate the
> closed system.
>
> New rad. fan switch(es) 3 so far make no difference.  I have to trigger
> on the fan with switch I've wired in to make fan cool to keep
> overheating at bay.  I drove the car during the winter and I started to
> notice the problem, but I guess it was cold enough out to keep from
> overheating.  Now with warmer temps it has become unmanageable and I
> can only drive the car for short trips.
>
> I'm afraid I need to pull the head, but wondering what I might find.  I
> don't want to go through another futile excercise like I when I changed
> my other nice motors if I have to do that.  Is there a possibility that
> an incorrect head gasket may have been installed? Any other clues
> before I do something drastic?
>
> The engine runs fantastic otherwise, with no lifter tick, smooth and
> good power.  Where do I go from here?  I am a few steps from having
> another parts car here, but this ones too nice to cannibalize.
>
> Ben