Temperature of stock thermostat?

[Cryptothedog]

I am having thermostat issues and want to replace it. I've seen a few that say they are 194 degrees and say that is the oem temp but then I have seen other thermostats that say they are 208 degrees and say it is the oem temp. Then I called the dealer and they said the one they have is 212 degrees. Which one is it? It's for a 2015 suburban.

To make things even more confusing. If I go to gmparts.com it shows an acdelco 15-11125 which is a 194 degrees thermostat. So I dunno. I want the coolest thermostat I can get without the need to reprogram fans

 

[Marky Dissod]

... want the coolest thermostat I can get without the need to reprogram fans

Anything under 194F would most likely be aftermarket.
Regardless, you won't NEED to reprogram any fans after buying a lower temp thermostat.

 

[viven44]

Dealer should be able to input the VIN and provide thermostat part #

What engine does your suburban have ? Too cool and it is proven that engine wear can actually increase although that would be more of an issue in winter time. In summer a cooler thermostat won't help in staying cooler. The system is going to achieve its equilibrium temperature based on the ambient temp, cooling capacity of your radiator, the cooling ability of your fan, engine and transmission power dissipation.

 

[Rygrego]

My 2016 Yukon 5.3 uses a 207 degree stat, yours would be the same.

 

[Cryptothedog]

Yeah, I was told by one dealer it was a 212 degrees tstat. Then another told me 194. In the past I've just run aftermarket and I'm sick of them failing so this time I'm gonna run the acdelco. So I'm gonna do an expirament. I'm gonna buy both and test normal operating temp and see if the 194 degrees does indeed run at 194 and not 207. I'm not going with the 212 though lol. I've got the 5.3 engine with 218k miles on it. Probably at least 100k of that is towing. I've put in an external transmission cooler and took out the transmission tstat and added the sure cool bypass kit. I'm trying to keep it as cool as possible. I tow a lot (30 ft camper, 2 side by sides and a boat. Obviously not all at once lol) No matter which one I tow, in order to get out of the city it is a climb over a mountain pass that is an 8 percent grade for about 10 miles and climbs over 4000 ft in that distance. So needless to say things get HOT any time but especially in 100 degree weather.

 

[Cryptothedog]

@viven44 thank you for replying. I'm glad I did some real world research because I have heard things in the past that are similar to what you mentioned in your previous comment. I have always wondered if that was correct or not. I honestly thought you were wrong but after real world testing, it turns out you are right.

I used an odb2 reader that gave me coolant temps. Both days were similar temps outside (101 degrees and 102 degrees respectively). I put in a brand new acdelco oem coolant temp sensor before this test. I drained the coolant from the radiator and all hoses and replaced with new dexcool fluid. I used a motorad thermostat that claimed to open at 208 degrees and an acdelco thermostat (part # 15-11125 with a 194 degrees temperature.

The only thing that may be different on my rig that may or may cause different results to others is that I have installed an aftermarket transmission cooler. So I don't know if that takes less work off the radiator for engine cooling or not. I also installed the sure cool bypass kit. So with my engine/Trans completely warmed up, my Trans runs at 142-145 degrees at idle and 151-155 during regular driving (not towing). Those two things may or may not cause my results to be different.

In general driving (fully warmed up, some stop and go and some highway, not towing anything) the temp of the motorad stayed consistently at 208.2 degrees at idle. While driving it of course fluctuated a little bit. It would stay in the range of about 206 -216 degrees.

In the same circumstances, the only difference I saw with the acdelco thermostat is that idle temps are around 204 degrees. While driving temps stayed between 204 and about 212. Definitely not the 14 degrees cooler temps that the 194 degree thermostat would imply.

 

[RST Dana]

The main point of the number is when the thermostat opens. When you are driving in colder weather, a lower number will open sooner and your heater may not be as warm as usual. If your rig normally operates at 212-214, then opening at 160 or 194 won’t change anything in warm weather.

 

[Cryptothedog]

The main point of the number is when the thermostat opens. When you are driving in colder weather, a lower number will open sooner and your heater may not be as warm as usual. If your rig normally operates at 212-214, then opening at 160 or 194 won’t change anything in warm weather.

My previous thermostat did in fact run cooler but it would also get stuck open sometimes. So something was wrong with it. Which is why I replaced it.

 

[Cryptothedog]

So what is the point of the thermostats that open sooner?

 

[Rygrego]

My previous thermostat did in fact run cooler but it would also get stuck open sometimes. So something was wrong with it. Which is why I replaced it.

The temperature of a thermostat is not its full flow temp, it's at that temp it will start to open and continue to fully open.

 

[RST Dana]

So what is the point of the thermostats that open sooner?

You need all the help you can get when you 12.5 to 1 CR in a 427 big block back in the sixties. It could open the 160 thermostat so quick, in finally knocked the center out of it to permit enough restriction to prevent overheating from coolant flowing/circulating TOO fast. This was way before all aluminum radiators and more efficient fans were reasonable. And I was a single college student using my hot rod as a daily driver.

 

[viven44]

@viven44 thank you for replying. I'm glad I did some real world research because I have heard things in the past that are similar to what you mentioned in your previous comment. I have always wondered if that was correct or not. I honestly thought you were wrong but after real world testing, it turns out you are right.

I used an odb2 reader that gave me coolant temps. Both days were similar temps outside (101 degrees and 102 degrees respectively). I put in a brand new acdelco oem coolant temp sensor before this test. I drained the coolant from the radiator and all hoses and replaced with new dexcool fluid. I used a motorad thermostat that claimed to open at 208 degrees and an acdelco thermostat (part # 15-11125 with a 194 degrees temperature.

The only thing that may be different on my rig that may or may cause different results to others is that I have installed an aftermarket transmission cooler. So I don't know if that takes less work off the radiator for engine cooling or not. I also installed the sure cool bypass kit. So with my engine/Trans completely warmed up, my Trans runs at 142-145 degrees at idle and 151-155 during regular driving (not towing). Those two things may or may not cause my results to be different.

In general driving (fully warmed up, some stop and go and some highway, not towing anything) the temp of the motorad stayed consistently at 208.2 degrees at idle. While driving it of course fluctuated a little bit. It would stay in the range of about 206 -216 degrees.

In the same circumstances, the only difference I saw with the acdelco thermostat is that idle temps are around 204 degrees. While driving temps stayed between 204 and about 212. Definitely not the 14 degrees cooler temps that the 194 degree thermostat would imply.

@Cryptothedog thanks for the kind response.

I agree with @RST Dana, the lower temp stats are just a safety margin in certain applications. Often used by Hotrodders in track applications, in fact many run straight water and no stat.

The higher temp stat (or OE temp I should say) is going to help the engine achieve operating temps quicker as well, thus reduce cylinder wear, burn off condensation, and reduce fuel dilution. This is especially important in direct injection engines like the new GM ones, and especially ones used in shorter trips.

 

[Cryptothedog]

@Cryptothedog thanks for the kind response.

I agree with @RST Dana, the lower temp stats are just a safety margin in certain applications. Often used by Hotrodders in track applications, in fact many run straight water and no stat.

The higher temp stat (or OE temp I should say) is going to help the engine achieve operating temps quicker as well, thus reduce cylinder wear, burn off condensation, and reduce fuel dilution. This is especially important in direct injection engines like the new GM ones, and especially ones used in shorter trips.

OK, that makes sense. Thank you for the explanation!

 

[Cryptothedog]

@Cryptothedog thanks for the kind response.

I agree with @RST Dana, the lower temp stats are just a safety margin in certain applications. Often used by Hotrodders in track applications, in fact many run straight water and no stat.

The higher temp stat (or OE temp I should say) is going to help the engine achieve operating temps quicker as well, thus reduce cylinder wear, burn off condensation, and reduce fuel dilution. This is especially important in direct injection engines like the new GM ones, and especially ones used in shorter trips.

One more question if you don't mind...so if the thermostat I'm running claims it starts to open at 194 but at idle I'm running between 204-208 does that mean it's basically always partially open? And if so would that actually cause me to overheat since the coolant doesn't sit in the radiator long enough to cool down?

 

[viven44]

One more question if you don't mind...so if the thermostat I'm running claims it starts to open at 194 but at idle I'm running between 204-208 does that mean it's basically always partially open? And if so would that actually cause me to overheat since the coolant doesn't sit in the radiator long enough to cool down?

If it is a 194F thermostat, it would be fully open at 204-208, and coolant should be flowing well through the radiator…. But I have heard the argument that the longer the coolant stays in the radiator is the better, but for sake of argument.... the likely ill-effect at idle (From a more open thermostat moving too much coolant) is less pronounced as there isn’t a ton of coolant moving due to the lower RPMs of the water pump.

At idle, the only cooling happening in the radiator is via the fan. On HD trucks a thermostatic fan clutch should engage fully and increase fan speed. I think the 1/2 ton setups (Tahoe, suburban) use an electric fan I’d assume above a certain temp (like 210F?) the fan would kick in full speed. Running the AC would increase the thermal load on the fan as well as the condenser is putting out a lot of heat…

A simple method to enhance cooling in the old trucks would be to upgrade to a severe duty fan clutch and if more serious also install a 3 row or 4 row radiator. I am not sure what kind of options exists in vehicles with electric fans. Sorry i have more experience with older 70s/80s trucks… are there fan motors that can turn on full speed at lower temps or spin faster?

Off topic, but given that you are after longevity and your engine has over 200K, you might want to consider moving to 5W-30.

 

[Cryptothedog]

If it is a 194F thermostat, it would be fully open at 204-208, and coolant should be flowing well through the radiator…. But I have heard the argument that the longer the coolant stays in the radiator is the better, but the effect at idle is likely less pronounced as there isn’t a ton of coolant moving due to the lower RPMs of the water pump.

At idle, the only cooling happening in the radiator is via the fan. On HD trucks a thermostatic fan clutch should engage fully and increase fan speed. I think the 1/2 ton setups (Tahoe, suburban) use an electric fan I’d assume above a certain temp (like 210F?) the fan would kick in full speed. Running the AC would increase the thermal load on the fan as well as the condenser is putting out a lot of heat…

A simple method to enhance cooling in the old trucks would be to upgrade to a severe duty fan clutch and if more serious also install a 3 row or 4 row radiator. I am not sure what kind of options exists in vehicles with electric fans. Sorry i have more experience with older 70s/80s trucks… are there fan motors that can turn on full speed at lower temps or spin faster?

Off topic, but given that you are after longevity and your engine has over 200K, you might want to consider moving to 5W-30.

How would changing the oil type help longevity? I currently and have always just run the recommended 0w-20. I have heard that thicker oils are bad for these engines.

 

[viven44]

How would changing the oil type help longevity? I currently and have always just run the recommended 0w-20. I have heard that thicker oils are bad for these engines.

Oh boy I don’t want to open a can of worms here but read this thread

Thread 'Oil weight for 5.3? 0-20 no good?'
https://www.tahoeyukonforum.com/threads/oil-weight-for-5-3-0-20-no-good.154235/

 

[RST Dana]

One more question if you don't mind...so if the thermostat I'm running claims it starts to open at 194 but at idle I'm running between 204-208 does that mean it's basically always partially open? And if so would that actually cause me to overheat since the coolant doesn't sit in the radiator long enough to cool down?

204-208 is not over heating, but more likely your normal operating temperature. If you added a thermostat over 208, it would raise your normal operating temperature.

 

[Marky Dissod]

How would changing the oil type help longevity?
I currently and have always just run the recommended 0W20. I have heard that thicker oils are bad for these engines.

If you press two pieces of metal together with the same amount of force long enough,
the ones 'protected' by 0W20 will make contact before the ones 'protected' by 0W30 (or 0W40, this may be a bit much for engines that don't work / play HARD).
Obviously 'enough' oil pressure mitigates contact, but it does NOT completely prevent it (otherwise engines would last forever!)

Also, 0W20 is subject to oil consumption sooner than 0W30. The longer you prefer to go between oil changes, the more you ought to use 0W30.

Some haven't taken advantage of paying attention to Lake Speed Jr's videos.
Others fail to notice that vehicles that get spec'd 0W20 / 5W20 in the US, get spec'd 5W30 in many other countries despite the engines being manufactured HERE.

 

[Cryptothedog]

I think the issue I had was due to the fact that my coolant concentration was too high. I have the 208 thermostat. Drained the coolant and replaced it with a 50/50 mixture and it has been perfect since. One of the times I changed the thermostat I must have accidentally put concentrate in and not the mix.