I have a 2002 Tahoe, 5.3L Vortec Flex-fuel with 75K miles. A couple of
nights ago my wife stopped at the end of the driveway (everything was fine)
to get the mail and paper. By the time she got back in, the Check Coolant
message was on the message center, and the temp gauge was pegged. She parked
it in the garage until I got home 10 minutes later. When I looked at it,
the expansion tank was full (overfull). There were no leaks.
I did get a little hasty and opened the cap too soon. There was still too
much heat and too much pressure, and I got a full boil-over geyser from the
tank as the coolant in the block boiled (pressure was keeping it from
boiling). Knowing from past experience that refilling a boiled-over block
can cause more damage, I waited a while, then refilled with water and ran
the engine. Seemed fine, but overheated again after 10 minutes of idling.
After picking up a thermostat, water pump and fan clutch at the parts store,
I discovered it was none of these, but that the radiator is completely
clogged. I noticed while disconnecting the hoses to check the thermostat
that coolant didn't rush out of the lower hose like you would expect from a
full, open-vent radiator. (Yep, this engine has the lower hose connected to
the thermostat housing, not the upper) Connected a garden hose to one end,
with 40 PSI got a slow flow out the other end.
Could this have been caused by switching from Dex-Cool to standard ethylene
glycol coolant? I'd heard so much negative press about Dex-Cool (in this
forum) that when the warranty ran out two years ago, I completely flushed
the system and refilled it with EG. That was at 36K miles, two years ago.
Last fall at around 55K miles I flushed it again and refilled with EG again,
and also replaced all the hoses (My preventative program is flush and
replace the stat every year, replace all the hoses and belts every three or
This seemed to come up pretty suddenly, as we have never noticed any cooling
issues before now, but this thing is hopelessly clogged. It is a single-row
aluminum core, will probably look for a 2 or 3-row brass core as a
Sorry, I run on too much here. Bottom line:
A. Could switching to ethylene glycol have caused the clog-up?
B. Would it follow that other aluminum passages (heads) could be suffering
the same fate?
C. Is there likely to be much damage to the aluminum heads after the
overheat (brief) and boil-over
Thanks in advance for you input,