4kq running cold- SOLVED (long)

Lines Peter Peterl at Warn.com
Mon Dec 30 10:31:02 EST 2002

About a year ago, I posted that my 4kq seemed to be running too cold in cold
weather.  The symptoms were that the water temp gauge would drop to the
first mark on the highway, but then rise to the middle of the range when
stopped and idling.  The rad. cooling fan would also cycle normally if
idling for a long period.
I first suspected a stuck open thermostat so I replaced it.  No improvement.
It is an 87C thermostat.
I then checked the accuracy of my dashboard water temp gauge by inserting a
borrowed thermocouple into the upper coolant hose connection at the engine.
After 5-10 minutes of idling, the fan cycles on and off as the thermocouple
reads 95-93C and the gauge is steady at the third mark (right above the
center of the gauge).  So I'm thinking no problem with the gauge, the water
must really be getting too cold on the highway.
At some point during the past year I replaced the radiator due to a small
leak, although this didn't change any of the temp. behavior and I think it's
I then proceeded to make a cover to block air flow for about 3/4 of the
radiator.  A short test drive showed that this did not raise the highway
temperature one bit.  Darn.
On a recent trip to Whistler, BC (the skiing was great, BTW) I noticed that
even while the water temp gauge was reading very low, the oil temp was
normal (as it always has been) and I get plenty of interior heat.  Both
conditions that seem to indicate that the water temp is OK and something is
wrong with my gauge.
I also noticed how dirty my engine would get when driving on wet winter
roads.  All the crap kicked up by other cars would completely coat the
engine.  I began to realize that air flow through the grill is directed
straight onto engine (not first through the radiator as on most non-5 cyl
cars).  Is my engine getting air-cooled while on the highway?  Not likely.
But what about the sender for the water temp gauge?  It's just sort of
hanging our there in the breeze.  Could it be getting cooled off by the air
flowing over it?  On my next fuel stop, I pop the hood and stuff a rag
around the sender to block the direct airflow.  Bingo!  The gauge is now
rock-steady at the 3rd mark whether I'm driving 80mph or stopped in traffic.
Long story short, there is absolutely nothing wrong with the cooling system
on my car, never has been.  It just took me a while to figure out why the
gauge has been reading low...
Now I'm wondering about the affect of the lower temp sender on the CIS
computer.  I probably want to block the airflow to this one as well.

Peter Lines

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