I'm guessing since this is in the 4.3L V6 forum that you have that engine.

Stant Superstat. I run one in a stock temp (195°F). The temps stay rock solid at 200°F +/- about 2°F. The Stant part # is 45119 for the stock (195°F) replacement thermostat. There's probably a 180°F in that line, but I don't know the part # off the top of my head.

Replace the pressure cap while you're working on the cooling system.

 

I had the same problem with a 160* thermostat causing a CEL in my 2003, so I went with a 180* and it has operated fine with plenty of heater temperature control.

I've had a couple of thermostats fail in the past, but both did so in the open position so no issues to the motor. The first one was a sold by Hypertech to go with their programmer, and the other was a cheap one from Autozone (don't remember the brand) that was the only option they had on the shelf at that time. As long as it fails open, you should be good. I went with AC Delco (12T31D) when I did my radiator last year.

 

yep 03 4.3

 

MotoRad Failsafe...better to fail open than closed.

 

bought the AC Delco 12T31D
found out it was just a reboxed Motorad
adding insult to injury Im sure its not a 180 as the highest it gets is about 170
by temp gun,gauge and scanner


This is the second thermostat thats too low,fuel trims are way too high because of low temps
and it takes way too long to go into closed loop.
Taking a real big hit on fuel economy other identical truck with a 195 gets about 3 MPG better

 

Temperature should be stamped on the thermostat.

 

I have always just used the higher end parts store brand. Never had a problem with any of them.

 

thought so too used to be stamped on the end of pellet. Have 2 here that arent
only stamped motorad
anyway amazon refunded got a Stant super 195 coming
cant find a stant super in 180

 

so curiosity got the best of me as one member advised against a 180
so I did a side by side comparison

no it wasnt run with one then switch but close enough for me
2 identical trucks save for one having sunroof.
same year engines in both run super.
allowed plenty of warm up time they are both running same amount of time
side by side
used 2 temp guns test both on a concrete stepping stone in the shade
.8* difference between them
please help me out and tell me what the 180* thermostat is doing wrong.


first is the 180*
vacuum 19 inches at idle
IAT 50*C
ENGINE 81*C
91*F ambient(using temp gun)
1st cat
in 300*F
out360*F
2nd
in 350*F
out285*F


2nd 195* thermo
19" vacuum @IDLE
IAT 57*C
engine 95*C


1st cat
in 400*F
out425*F


2nd
in400*F
out 317*F

 

so curiosity got the best of me as one member advised against a 180
so I did a side by side comparison

no it wasnt run with one then switch but close enough for me
2 identical trucks save for one having sunroof.
same year engines in both run super.
allowed plenty of warm up time they are both running same amount of time
side by side
used 2 temp guns test both on a concrete stepping stone in the shade
.8* difference between them
please help me out and tell me what the 180* thermostat is doing wrong.


first is the 180*
vacuum 19 inches at idle
IAT 50*C
ENGINE 81*C
91*F ambient(using temp gun)
1st cat
in 300*F
out360*F
2nd
in 350*F
out285*F


2nd 195* thermo
19" vacuum @IDLE
IAT 57*C
engine 95*C


1st cat
in 400*F
out425*F


2nd
in400*F
out 317*F

Those trucks aren't identical. The second truck, the one with the 195° thermostat has a minor issue that's making it run rich.

Does either truck have an AIR system (AIR pump plus pipes to the manifolds)?

What are the fuel trims on the second truck? I'm betting they are significantly positive.

Also, did you run your test after letting them idle for a while and warm up that way? Or did you run your test after driving more than 5 miles under similar conditions? Testing immediately after driving is probably a better test of what's happening under real world conditions. Most folks don't own trucks to leave them parked idling "warming up." Just sayin'.

 

I give my vote to Stant. I think most thermostats should fail in the open position.

 

yea since you can control your temp via fan control vs an engine thermostat
do crank it up to 195 and see if it makes any difference.
I forgot to mention that the coolant temp and IAT measurements were with my snap on scanner.
The 180* vehicle has a new Delco temp sensor thats in the cylinder head,other one is the factory
OEM,so dont know how accurate it is


But the whole point of doing this is to see if indeed the 180* thermostat does create unburned
fuel that would heat up the catalytic converter.

 

Got it, that makes sense. I'll have to install a 195* t-stat, since the 180* one is enough to keep the temperatures down most of the time; the stock clutch fan wouldn't engage until around around 195-200*.

I haven't checked the temperatures of my catalytic converter yet, but I can do that when I run my tests. Only difference is I have a Magna-Flo high flow cat. I'll still do a before and after to see the difference on my truck.

 

Was a 180*F thermostat ever an OE temp?

 

AFAIK, never on a 4.3L V6 in an S series.