4kq overheating...

[ben swann]

I've received some very helpful information on this problem and have
not tried eveything I can yet before resorting to major surgery.  It
seemed that following the suggestion to bleed the radiator using the
bleed bolt was working.  Engine was keeping it cool when I started up
and idled for about 5 min and then drove around for about 5 min.  I
parked engine idling and watched the temp slowly creep up waiting for
the fan to come on.  Radiator seemed to be a little more uniform temp,
but still cool at the bottom.  The coolant reservior began to
overpressure the cap and I extimate a good half gallon came out.

Temp. rose but not as drasically as I'd seen - the guage has three dots
and it rose to the middle dot - I forced the fan on with the extra
switch I'd installed, it kept from radically overheating, but if I left
running it would have surly pegged the guage.  Hot air coming from fan
indicates to me that the radiator is removing some heat.

Maybe I still have air pockets.  I have never had this kind of problem
with an overheat and never thought about bleeding the system as I have
done my fair share of radiator replacements, etc.  Elliott describes
below what may be happening, but why is the air getting trapped if that
is the case?

So although we may have been onto something with the collective wisdom
as below and from others, I don't have this one solved yet.

Things tried and obeservations:
- I do not see the little hose to overflow putting out any coolant as
Dave C. and Huw indicate should happen, and don't really observe any
flow to/from the reservior, but it is opaque and hard to see anything.
AFAIK the hose is clear, but will double check later.
- Mixture is about 50% coolant 50% distilled water.
- New water pump
- passages seem clear as hose can pass water through the block
- tried 3 different radiators and the one installed currently was
keeping the guage at mid-level in another 4kq.
- new fan switch, but doesn't kick fan on.  I know there may be a
cooler operating switch, but in any case I can tell the bottom of the
rad stays to cold  - at best warm to touch, even when head temps will
fry an egg.
- New thermostat was tried - currently running with no t-stat for
testing.
- heater blows hot when turned on.
- when I pulled the water pump, I did not observe any clues that there
is massive scaling or buildup in the engine.  I have yet to remove the
small line from water pump around to heater and back of block yet and
check for blockage.

I'll keep trying these great suggestions - I suppose next is to remove
the heater line and fittings.  Is there any good chemical/soution that
is good for cleaning the cooing system?

Ben
[Ben,
Maybe air in the radiator would result in no coolant spraying into the
overflow tank from the small hose attached to the top of the radiator.
If so, I think this could cause overheating.  I've heard that if you
block off that hose it will definitely result in overheating.
---------------
Dave C.

[Earlier Huw  suggested the test below...

here is an interesting test, if you still like to run that engine while
risking all the parts that don't like extra heat (although this test can
be done cold, so it's ok).

With the thermostat out (so it can be done cold), turn engine on.

Go under the hood.  Look closely at the coolant expansion tank.  If you
can see through the plastic, so much the better (if not, get a new one).

Rev the engine up - you should see coolant spraying into the x-tank from
the small hose attached to the top of the radiator.  You can do it with
the cap off if the tank has become opaque with age.

No flow there >>>  Water pump bad.
Flow there >>>  Look up obscure pagan rites to exorcise your engine...]]

- AND -
[----- Original Message -----
From: veetesse <veetesse at hotmail.com>
Date: Tuesday, June 3, 2003 11:36 am
Subject: 4kq overheating...

Ben...

That bleed bolt at the top left of the radiator, if you look at it, is
actually flat on one side to let air out.  What I normally do is
backfill the block and the expansion tank, start it up and let it run
for a few minutes with the bleeder screwed out or removed.  I place a
pan (rubbermaid bus pan for restaurants) under the radiator and then as
the engine warms up, it will eventually "geyser" out the hole and into
the pan...  That's my cue to tighten up the bleeder bolt.  Kind of
messy, but does eliminate the air. You probably already knew about
that, but I thought I'd include it anyways...

Your overheating syndrome does indeed sound like what happened to me in
my CGT when the water pump died...however, as you've said, we can
probably rule that out at this point.

In my situation, the "cool on the bottom, boiling hot up top,
pressurized hoses, marginal heat" behavior was explained to me in my
situation as the block being low in coolant, then actually having the
remaining coolant vaporize in the block...creating steam and
pressurizing the system.  In my case, it overpowered the cap and shot
more coolant out on the ground.  Now, if you had air in the system,
that would certainly account for low coolant level (big bubble of air
in the block / hoses / radiator) and might possibly cause what you've
been describing.

I hope that's it... I'd hate to see you have to pull the engine apart or
swap it because of something like this...

Elliott]