Truck just turned over 75k miles. All winter long the one thing this
truck did well is get heat to the coldest passengers. Then last week,
with no signal of impending doom, all she does is blow cold air.
First thing I thought to check was the radiator. The 'overflow' tank
(not sure that's what it's actually called) had nothing in it, so I
let the engine cool and I opened the radiator cap. What I saw shocked
me. Sludge on the cap. I thought it was a huge amount, but I wiped
it off pretty easily then turned my attention inside. All I saw were
rusted coils. No coolant. So that morning I brought it into a Tires
Plus shop for a flush and fill (with chemical clean as they advertised
it). I was hoping that the change would give me some heat (as it's
turning cold up here in the midwest again). Not to mention clearing
any residue out so it doesn't wreck the motor! First thing I tested
that evening was the heat. Very little warmth coming out after
driving the vehicle for 30 minutes. It seems to not overheat, never
have I seen it get over 200 (usually about 180-190 I'm guessing). My
oil pressure seems high (usually about 40), but I've changed the oil
many times and it remains the same, so I'm guessing consistency is
good (I'm no car expert though). Naturally that night I started
checking the web out, and found out that systems with Dex-Cool from GM
are ticking time bombs. I'm not sure what was in the radiator before
(as I just purchased this car about 25k miles ago). From the sounds
of it I'm hoping it wasn't this Dex-Cool. The shop I took it to put
some generic fluid in and said it would be okay. And the press I'm
reading agree as long as the system if flushed before the change is
made. I knew the heater core could be the problem, but most of the
articles I've read online said when you turn on defrost, you'll
generally get a film of antifreeze on the window. That hasn't
happened (but the antifreeze was low obviously). I'm going to do a
good clean of the windows tonight and try that afterward. I don't
smell anything 'sweet' while the defrost is on either. Is there any
other way to check the Heater Core? From what I'm reading in the
articles, I don't really want to just start throwing money at it if
it's going to be a sludge problem. Cure the problem, then replace the
parts me thinkst. I don't think the thermostat is bad as the engine
shows no sign of overheating at this point - even when idling for 1/2
hour as a test. As a side note, late last summer the beast didn't
throw as much cold air with the air conditioning either. But as
winter was approaching, I really didn't think much of it and planned
on having the airconditioning system checked out and recharged if
necessary.

Any ideas on how I can make sure the radiator is clear of sludge
before trying other things? I recall reading that there is powder
chemical you can put into the radiator and drive around for 6 hours
then flush and fill again. Anyone ever heard of that? If so, do you
know it works? I'd much rather spend a cpl hundred repeatedly
flushing/cleaning the system than replacing all the parts. Or is the
wise move to get out from under this money trap ASAP? I can easily
sell it for what I owe on it.

Thanks for any ideas.

Todd.

On 5 Apr 2007 06:12:49 -0700, todd.frahm (AT) gmail (DOT) com wrote:


At this point I would suggest that for starters you pull the radiator
and have it "boiled" out and cleaned at a radiator shop. Next reverse
the hoses going to heater core to change coolant flow direction to
help clean core if it is clogged. After replacing radiator after it
has been cleaned I would flush system again to clean heater core
(either that on have it removed and flushed too) EPA regulations have
greatly limited the effectiveness of over the counter flushes these
days and have radiator cleaned manually will mean the flush can focus
on the rest of the system.. One the coolant, the problem is not so
much Dexi as it is the engine itself. It has a mixure of metal in it
(castiron and aluminum) which causes a galvanic reaction with coolant.
With Dexi GM attempted to control this while still using a 50/50 mix
which does not cut it long sometimes. When you replace coolant use at
least a 60/40 mixture and your problem will not return. Also GM heater
can be very sensitive to coolant level and can air lock and provide no
heat if cooling system is not full. Sometimes it takes a few heat and
cool cycles to purge the air from it. Using a 7 to ( pis cap will
speed the purging process up some. (I use 7 to 9 PSI Stant caps all
the time regulalry with 60/40 or 70/30 and I have never had any over
heating issues or sludge build up issues and the first thing I do with
any new car is increase the antifreeze consentration after I buy it)
Sounds like previous owner did little more than drive it for a while
and then dump it.
-----------------
TheSnoMan.com

On Apr 5, 9:13 am, SnoMan <a... (AT) snoman (DOT) com> wrote:
Thank you for the quick reply. I truely appreciate it. I'll give it
a shot this weekend. Have to take care of the baby!

On Apr 5, 9:12 am, todd.fr... (AT) gmail (DOT) com wrote:
Todd, the thermostat can stick open as well as stick closed. If it
sticks open the heater will blow luke warm at best.