160 thermo. Heat spike at 107° weather.

[tRidiot]

My understanding of the thermostat temp is when it opens to allow the coolant out of the engine block and into the radiator to be cooled off.

So a 160 thermostat will open sooner, allowing flow continuously above that point.

The 187 thermostat will allow the temp to be higher in the motor before opening. This is helpful in colder climates when you want your motor to warm up better/faster is my understanding.

Hotter outside temps won't change how these thermostats behave, and it won't allow your truck to cool better when the outside temp is hot with either one.

That's the way I understand it... the higher temp thermostat would allow your engine to run warmer before opening to cool it off - helpful in the winter to get more heat into the cab. This is what happened to me when I changed to a 187 themostat - then it stuck and I blew a head gasket. lol

 

[HD_LS]

My understanding of the thermostat temp is when it opens to allow the coolant out of the engine block and into the radiator to be cooled off.

So a 160 thermostat will open sooner, allowing flow continuously above that point.

The 187 thermostat will allow the temp to be higher in the motor before opening. This is helpful in colder climates when you want your motor to warm up better/faster is my understanding.

Hotter outside temps won't change how these thermostats behave, and it won't allow your truck to cool better when the outside temp is hot with either one.

That's the way I understand it... the higher temp thermostat would allow your engine to run warmer before opening to cool it off - helpful in the winter to get more heat into the cab. This is what happened to me when I changed to a 187 themostat - then it stuck and I blew a head gasket. lol

Correct on all counts. And the theory repeated by many, about wanting to restrict flow rate through the radiator to give it more time in the radiator to cool, is complete BS. See the Tech tip #3 on the Stewart Water pump website: http://www.stewartwaterpumps.com/

For the OP, If you don't need better cab heating, leave the 160 in. You need a better radiator and or a fan that moves more air, to get the temps cooler.

 

[Doubeleive]

Correct on all counts. And the theory exposed by many about wanting to restrict flow rate through the radiator to give it more time to cool is complete BS. See the Tech tip #3 on the Stewart Water pump website: http://www.stewartwaterpumps.com/

For the OP, If you don't need better cab heating, leave the 160 in. You need a better radiator and or a fan that moves more air, to get the temps cooler.

I think you may be confused with the restrictor used in these trucks, there is a small line that goes from the radiator to the coolant reservoir, if there is no flow restriction it just bypasses the thermostat and absolutely has a effect

 

[HD_LS]

I think you may be confused with the restrictor used in these trucks, there is a small line that goes from the radiator to the coolant reservoir, if there is no flow restriction it just bypasses the thermostat and absolutely has a effect

Understood. I was referring the the OP's statement "Is it because the 160 thermo is not closing and keeps the coolant circulating? If I swap for the 187 it should keep the coolant longer in the radiator right?"

And yes the restrictor, since flow in that small hoses bypasses the thermostat, is required to get faster warmup, and more interior heat in the winter. However, if you wanted to really max out hot temp cooling, with an aftermarket radiator that did not have a restrictor in that small hose fitting: You could put a valve in that small hose path, to bypass the restriction for max raditor flow when you need max cooling.

 

[Doubeleive]

for reference a good working system should show the temp go up to normal (usually either just before the middle mark or just past middle, or in the middle it can vary from cluster to cluster) and it should stay there and never move.
mine moved once while driving 95mph up a 6% grade at 9000 ft @75deg ambient for a extended period of time, it moved up to maybe 220-225 and after I let off for a bit it went back to normal
if your temperature gauge is moving at stop lights or heavy traffic or idling with the ac going then something needs to be addressed, it shouldn't matter if it's 120deg outside.
usually it's the radiator or the radiator has crap in the fins bugs/dirt/leaves, etc. the typical lifespan of a radiator is 5 years.
I flush mine annually and run citric acid thru it in the process (radiator flush) this keeps the system healthy

 

[Fless]

Also make sure that your fan shroud is intact and in place, both top and bottom pieces.

 

[ROGELIO A GUZMAN]

203 is a heat issue? I idle at about 205 degrees in the high desert summer when the engine is fully warmed up. Freeway cruising it goes to about 197.

02 yuk, 4x4, 5.3 FF, stock. 206k miles. Original rad.

whats the highest u seen your temp go up?

 

[ROGELIO A GUZMAN]

Also make sure that your fan shroud is intact and in place, both top and bottom pieces.

they are intact

 

[ROGELIO A GUZMAN]

for reference a good working system should show the temp go up to normal (usually either just before the middle mark or just past middle, or in the middle it can vary from cluster to cluster) and it should stay there and never move.
mine moved once while driving 95mph up a 6% grade at 9000 ft @75deg ambient for a extended period of time, it moved up to maybe 220-225 and after I let off for a bit it went back to normal
if your temperature gauge is moving at stop lights or heavy traffic or idling with the ac going then something needs to be addressed, it shouldn't matter if it's 120deg outside.
usually it's the radiator or the radiator has crap in the fins bugs/dirt/leaves, etc. the typical lifespan of a radiator is 5 years.
I flush mine annually and run citric acid thru it in the process (radiator flush) this keeps the system healthy

With the 16o thermo my Yukon is normally at 170-180. so when I saw the temp rise I kinda panic. but from what I hear, 200-220 is pretty normal operating temps. i bought the Yukon with a bad water pump leaking and a plugged-up china replacement radiator. also, the clutch was bad. all replaced with OEM parts. I just thought it was a good idea to put a cooler thermo.

 

[bigdog9191999]

Correct on all counts. And the theory repeated by many, about wanting to restrict flow rate through the radiator to give it more time in the radiator to cool, is complete BS. See the Tech tip #3 on the Stewart Water pump website: http://www.stewartwaterpumps.com/

For the OP, If you don't need better cab heating, leave the 160 in. You need a better radiator and or a fan that moves more air, to get the temps cooler.

the only thing leaving a cooler thermostat in will do is take the engine longer to get up to correct operating temp, throwing off fuel tables and such until it does. most people dont realize it actually causes worse mileage in most cases, esp if the cooling system is working well and keeps the temp low as it will keep it cool enough the pcm will continue to try and compensate. if one was to keep the cooler stat having the pcm tuned to coincide with this is the only way to make it work mostly correct, and there still is no real benifit as they where designed to run a little warmer.

for reference a good working system should show the temp go up to normal (usually either just before the middle mark or just past middle, or in the middle it can vary from cluster to cluster) and it should stay there and never move.
mine moved once while driving 95mph up a 6% grade at 9000 ft @75deg ambient for a extended period of time, it moved up to maybe 220-225 and after I let off for a bit it went back to normal
if your temperature gauge is moving at stop lights or heavy traffic or idling with the ac going then something needs to be addressed, it shouldn't matter if it's 120deg outside.
usually it's the radiator or the radiator has crap in the fins bugs/dirt/leaves, etc. the typical lifespan of a radiator is 5 years.
I flush mine annually and run citric acid thru it in the process (radiator flush) this keeps the system healthy

those of us in cold climates see as much fluctuation as anybody. when cold i can watch the gauge go up to temp, the stat open and temp comes back down, levels out when stat closes and starts climbing again. some vehicles do it more that others, but when you have a good large cooling system and alllllll that cold coolant is in there it can cycle enough back through the engine too close the stat and not have all the system coolant up to temp yet, and can take a few cycles to level out. but once it does it stays steady as it should, unless it is really really cold.