[AT] HELP I'm stumped. truck problems, overheating

[charlie hill]

Darrell,  the fan is electric and it's running fine but thanks.

Bo,  I think I found the problem or at least part of it.  I think I did
have an airlock.  I filled the reservoir twice with a gallon of antifreeze
and then close to a gallon of filtered water.  I thought it was full
but when I went back out after writing I found it low.  I had filtered
the coolant I drained out (or all I caught of it) and let it settle so
I put some of that back in to make up the difference.  It APPEARS
to be running right now.  However,  I see some water in the tail pipe
but it is clear and odorless so I figure it's just condensate from heating
up a cold engine and exhaust.  You know how humid it is on the coast.
I'll run it down the road and dry it out and see what happens.  However that
still doesn't explain why the old thermostat is working fine in a pan or 
water.

I think if it was a cracked head it would overheat all the time or show some 
other
signs.  I guess I'll find out soon enough.  Unfortunately I'm going to have 
to pull
it apart again because I must have not gotten the housing flange clean and I 
have
a real slow leak or seep.  It's no big deal at all.  I just hate to loose 
that 15 bucks
worth of antifreeze I just put in it and the way the truck is made there is 
very little
way to catch it for reuse.  I'm going to try.

-----Original Message----- 
From: Bo Hinch
Sent: Saturday, August 29, 2015 3:48 PM
To: Antique tractor email discussion group
Subject: Re: [AT] HELP I'm stumped. truck problems, overheating

Charlie , here are some thoughts you might check out and the very last one
is one I`m sure you don`t want to hear .

You could also scan the computer to make sure she's actually running hot.
High millage? Them engines are* common to crack heads from what I've seen .*

Make sure you bleed the system correctly, you may have fixed with the
thermostat and broke it at the same time. Vacuum filling the system is the
best way also make sure your 50/50 on the coolant mix.

Another thing that is commonly overlooked is a plugged heater core. The LS
engines use the return flow from the heater core to heat up the t-stat and
make it open. If the heater core gets blocked it will overheat in a hurry.
Fought this on a 4.8L before where it was running 240-250 no matter what.
It had heat, but not good heat out the vents. Took the 2 lines off at the
heater core and back flushed it for a minute, hooked it back up and it
dropped down to 185 and stayed there. Also like said above could be a bad
stepper motor in the cluster, and the coolant temp sensor could be bad
telling it that it is hotter than it actually is.
__________________

Most common issues we have seen on a number of trucks is the nipple on the
radiator that goes to the top of the coolant bottle being plugged/melted
from an overheat caused by something else. It is a specific size and when
they overheat it tends to shrink the orfice and cause one to overheat. It
is supposed to be .083. We use a drill bit by hand to open it back up. The
other issue is the tubes running from head to head on the front and
sometimes on the back under the edge of the manifold get stopped up.
__________________

It was the 01- early 06 heads with the CASTECH casting mark under the valve
cover that had the cracking problem. And when they cracked it would have a
slow coolant loss to the crankcase of the engine.
__________________Bo Hinch in s/w louisiana

On Sat, Aug 29, 2015 at 2:25 PM, charlie hill <charliehill at embarqmail.com>
wrote:

> Ok guys, my 06 GMC 5.3 liter engine started
> overheating when first started up.  It would get up
> to about 220 or 230 degrees.  I could turn the heater
> on and get NO hot air flow.  Then all of a sudden
> it would start to cool and the heater would blow hot air.
> OK easy, bad thermostat.
>
> I go and get a new t-stat and put it in.  Same problem except
> worse.  Now it gets up close to 250 before it starts to cool down.
> I took the old thermostat in the house and put it in a pot of water on
> the stove with a cooking thermometer in it.  It opens and closes as it
> should.
>
> Anyone got an idea what is going on?  For those not familiar with
> the 5.3 GM engines the t-stat is not in the intake like GM motors of
> old. It's in the front of the water pump housing so it should not be
> prone to having an airlock at the thermostat.   I see no sign
> of bubbling in the coolant.  I'm not loosing an appreciable amount of
> coolant and there is no sign of coolant it the water or out the exhaust.
> I did however have to add some coolant a few weeks ago which is unusual
> and I have smelled an odor that smells like a coolant leak.  It's the same
> odor you smell in the cab when a heater core is leaking.  But I haven't
> found
> any sign of a leak anywhere.
>
> Right now I'm sitting at home with both of my vehicles not running.  I 
> need
> answers quick.
>
> Thanks
>
> Charlie
>
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