Thermostat Temp Change, Why 200F for 10-12, but 190F for before and after?

[MichaelOverfield]

I recently did the coolant flush/fill and replaced the thermostat. I ended up with the 200F thermostat, used on the '10-'12 trucks, but seems mine, a 2009, had a 190F originally, and the '13 and newer also have 190F. Does anyone know why this change was made for those years, and if there are any pros/cons for use of the 200F over the 190F thermostat?

Thanks.

 

[sag2]

It was done for emissions. Legally you need to use the thermostat that the truck was built with. I suppose from a technical standpoint any shop that changed a 200 to a 190 would be in violation of emissions laws. Don't give it much more thought from there, it will run the same with either.

 

[Shadrach]

I'm sure glad we don't have all them stupid laws up here. I can change from a 6.7 to a 5.9. I can change from gas to diesel or blue to yellow, remove anything or add anything I want and no one says Boo.

BTW I am NOT a fan of "Rolling Coal" or straight pipes.

 

[MichaelOverfield]

Ok, I'd expect the 200F to provide more efficiency and lower emissions generally, but I'm not sure why they went from 200F back to 190F for '13 and beyond. The only downside I can seen for higher temp is maybe lower oil life, but then again with fuel dilution a possible issue, the higher temp would help cook off fuel that made it to the oil pan.. so it is a mixed bag. I'm going with the 200F for now and will see if it affects economy in anyway, I expect to see a slight improvement.

 

[AH64ID]

You should see a slight improvement in fuel economy but if you tow I would switch back to the 190° thermostat or you will be giving your fan a big workout and that will more than negate any mileage gains you may see with the 200° thermostat.

The 10-12 did go to 200° to help with emissions and it's not needed for the 13+ emissions setup. The added temp probably did have an effect on oil life but that's no longer an issue on the 13+.

 

[RustyJC]

You should see a slight improvement in fuel economy but if you tow I would switch back to the 190° thermostat or you will be giving your fan a big workout and that will more than negate any mileage gains you may see with the 200° thermostat.

I tow the 5th wheel in my signature with a 2011 which has a 200 degF thermostat. The fan very seldom engages - it doesn't come on until 219 degF as shown on the EVIC. The only time it will come on at highway speeds is on a long pull up a decent grade in ambient temperatures above 90 degF. Once engaged, it will pull the temps back down in 20 seconds or so and shut off.

Granted, with a 190 degF thermostat, coolant temperatures would have to rise farther from normal before the fan kicks in, but in either case, the fan only kicks in after the thermostat is already wide open and circulating all the coolant it can.

Rusty

 

[AH64ID]

I tow the 5th wheel in my signature with a 2011 which has a 200 degF thermostat. The fan very seldom engages - it doesn't come on until 219 degF as shown on the EVIC. The only time it will come on at highway speeds is on a long pull up a decent grade in ambient temperatures above 90 degF. Once engaged, it will pull the temps back down in 20 seconds or so and shut off.

Granted, with a 190 degF thermostat, coolant temperatures would have to rise farther from normal before the fan kicks in, but in either case, the fan only kicks in after the thermostat is already wide open and circulating all the coolant it can.

Rusty

Your 2011 fan is programmed around a 200° thermostat and the OP's 2009 fan is programmed around a 190° so it's not a valid comparison.

 

[RustyJC]

OK, I missed that his was originally a 190 degF truck. In that case, I'd certainly stay with the 190 degF thermostat as well unless I could reset the cooling fan activation and shutoff temperatures.

Rusty

 

[MichaelOverfield]

Your 2011 fan is programmed around a 200° thermostat and the OP's 2009 fan is programmed around a 190° so it's not a valid comparison.

Great feedback here and thanks.. from the data above, it seems the program fan kicks in at about 20F over the thermostat open, for the 200F it goes on at 219F... for mine with original at 190F, I could expect an on at 209F or so if that is a valid comparison. I know it does not kick on at 200F since it does not go above that now.

When I do tow, the trailer is small for what the truck can tow.. I have yet to see the fan kick on (with the original 190F thermostat), and that was even pulling at highway speed up Grapevine outside LA in the heat.. but it is something I definitely need to consider.

In contrast the 2 prior Duramax trucks, did call on the fan for that same pull and same trailer.. the cooling system on the Cummins seems to be far superior to the Duramax.

 

[AH64ID]

The thermostats all have a wide range of operation. The 190° thermostat crack at 190°±3° but isn't full open until 207°. The fan kicks on full around 215°.

The data is harder to find on the 200° thermostats but extrapolating from the 180° and 190° thermostats I figure they crack at 200°±3° and are full open at 215°-217° which is right where the fan will be kicking on, when it doesn't need to kick on until ±220°.

 

[Tinman]

What are the other factors/trigger to turn on the fan besides the coolant temp. My 06 fan turns on all the time. For instance, over 60 degrees ambient temp anytime the compressor is on the fan is on. It's on enough to be aggravating. I think the clutch is bad, but all the factory service stuff I saw was about diagnosing a fan not coming on when it should.

 

[AH64ID]

There will be a separate control based on a/c use, but I rarely ever hear mine or see it commanded on with my Touch.

Maybe it's just louder than you think?

 

[RustyJC]

The data is harder to find on the 200° thermostats but extrapolating from the 180° and 190° thermostats I figure they crack at 200°±3° and are full open at 215°-217° which is right where the fan will be kicking on, when it doesn't need to kick on until ±220°.

My truck with the 200 degF thermostat stabilizes between 199 degF and 201 degF on the Interstate running unloaded on level terrain on a 90 degF day. Towing our HEAVY 5th wheel under the same conditions, it normally runs at 203 degF. On long grades pulling the 5th wheel, it will climb slowly but steadily to 219 degF (as stated earlier) where the fan kicks fully on and drops the temps quickly back to the 205 degF range before cutting off, even if we're still pulling the grade.

So, where's full open? Who knows.

Rusty

 

[Tuesdak]

What are the other factors/trigger to turn on the fan besides the coolant temp. My 06 fan turns on all the time. For instance, over 60 degrees ambient temp anytime the compressor is on the fan is on. It's on enough to be aggravating. I think the clutch is bad, but all the factory service stuff I saw was about diagnosing a fan not coming on when it should.

The fan comes on for high AC head pressure. Say you have a cold engine ~120 degrees like in Phoenix, AZ and turn the AC on high. The Condenser will be 160 degrees before you make it 1 block in the 120 degree weather. So the Modern computer controlled fan will be turning on at the end of the block for AC performance unlike the Obsolete Spring thermal fan clutch GM uses... That obsolete spring thermal clutch can take until the engine warms up before it sees enough hot air to come on meanwhile the AC performance suffers and overheats the system.

In your case you need to diagnose the AC system as to why the head pressure is so high or faulty high pressure sensor/wiring. Bugs plugged the condenser/ fins bent, overcharge, plugged orface tube, lack of system oil burning compressor up...

 

[MichaelOverfield]

What are the other factors/trigger to turn on the fan besides the coolant temp. My 06 fan turns on all the time. For instance, over 60 degrees ambient temp anytime the compressor is on the fan is on. It's on enough to be aggravating. I think the clutch is bad, but all the factory service stuff I saw was about diagnosing a fan not coming on when it should.

Don't forget, typically the A/C compressor is engaged when any de-frost mode is selected, even in winter, that could be a factor. The fan will also spin when the clutch is not engaged, just not at full engine RPM, that could also be a factor in your case, it is an engine driven fan after all. Only the electric fans are idle when not needed.

 

[promisedland]

May i take a seat?.... what rpm range do our fans run? Since i have been watching on my Touch i have seen 400'is to 1200 rpms. No towing, Just D.D.

 

[Tinman]

This has been going on a while. Years. Last summer, my compressor clutch puked and I just took it to the dealer for replacement compressor. So I would think the charge, oil, etc is spot on now. No change the the behavior of the fan. It' only a problem in summer, I forget about it in winter. On a hot day traveling at slower hwy speeds (55-60 mph - not so noticeable at interstate speeds), I can hear the fan engage and disengage repeated over 30 -60 seconds. It doesn't get to fully engaged.

 

[EDankievitch]

The heat was way much more better/ hotter on my 2012 with the 200 degree T stat than my 2013 with the 190 degree stat.

 

[MichaelOverfield]

UPDATE:

Running the 200F thermostat in my 2009 seems to be without any issue, even towing, though I'm not even close to truck limits with my rig. I've not had temperature go high enough to cause the fan to kick on.. I've been below 210F even on hills, in 5th gear, at highway speed. So from what I've seen, it is possible to use the 200F in a 190F stock truck.. but any coolant system issues may change that, I do have fresh coolant, and added Purple Ice additive with the new coolant, so it's possible that is a factor in keeping coolant efficiency high, and the fan clutch off, even with a smaller band from t-stat full open to fan engage.. just data out there from real world use..

 

[Tuesdak]

This has been going on a while. Years. Last summer, my compressor clutch puked and I just took it to the dealer for replacement compressor. So I would think the charge, oil, etc is spot on now. No change the the behavior of the fan. It' only a problem in summer, I forget about it in winter. On a hot day traveling at slower hwy speeds (55-60 mph - not so noticeable at interstate speeds), I can hear the fan engage and disengage repeated over 30 -60 seconds. It doesn't get to fully engaged.

Possible the dealer tech took a shortcut and didn't flush the AC system with a new compressor. This would leave old oil in the system and new compressor with full oil charge may have too much oil in the AC system. Result is poor cooling and high head pressure as it chokes on the excess oil. AC head pressure triggers the cooling fan. Have whoever watch the AC head pressure (AC High Side PSIG) on a scanner when the fan is acting up. Also hook a gauge set up on it and make sure the AC sensor is in the ballpark. Possible system overcharge does the same high head pressure to trigger the cooling fan.