Coolant/Stat Change
11-28-2012, 04:44 PM
#1
Drifting
Thread Starter
Coolant/Stat Change
With 18,000 miles on my bone stock 2008 C6, I decided to change the coolant. It has been bugging me for a long time that my cruising temps were 198 degrees F. The boys at GM want the LS* engines to cruise in the 190's. I prefer running at the lower end rather than the higher end, so I decided to try a 180 degree thermostat, 8 degrees less than the stock GM thermostat.
My Replacement Thermostat
After much internet research, I decided to go with a Lingenfelter 180 degree thermostat. This is in fact a Motorad, which has a good reputation. I tested the thermostat on the stove with an accurate digital thermometer (and candy thermometer). As per spec, it started to open (very slightly) at 180 degrees; at 190 degrees it opened about 2mm (0.08"); and appeared to be fully opened around 199 degrees about 6 mm (0.24"). It appeared to open linearly. Please note these are rough numbers.
My “stovetop” test:
I did a side by side comparison with the stock GM thermostat. The 188 degree GM thermostat is much more rugged and heavier, and IMHO, of a better quality. This is not to knock the Motorad, but it was very apparent when looking at them side by side.
The only markings I found on the GM unit were “NTCL 86 degree C” and what looked like “LDW” on the center shaft.
My concerns with the Motorad were threefold: The GM appeared to be more rugged, the Motorad length plate to plate was slightly longer, and the Motorad lower plate had holes vs the GM one which is a solid disk with slight ridges on the underside.
Comparison Top View GM and Motorad (GM on LHS):
Comparison Side View GM and Motorad (GM on LHS). Note that the GM Plate To Plate distance is slightly shorter.:
Comparison Bottom View GM and Motorad (GM on LHS). Note differences in bottom plates.:
The lower plate (reverse poppet) is what blocks the inner opening in the water pump, ensuring that coolant flows through the rad, and preventing most coolant from circulating back through the block when the thermostat is opened. My thoughts were that the GM one would do a better job at this.
View inside water pump. Note the flange where the lower plate contacts. This is where the coolant recycles back into the block when thermostat is closed. It should be closed by pressure from the lower plate when the thermostat is opened.:
As per their web site, and my discussions with Motorad, there is no exact alternate thermostat for the 2008 C6 LS3 (2009+ use a different stat/housing/water pump). If you want an exact Motorad thermostat for your 2008, the only option is a 188 degree.
I would guess that Linenfelter did his own research and came up with this 180 degree alternative. By the way I am not knocking Motorad or Lingenfelter in any way - I’m just saying.
My Procedure
I opened the reservoir cap and the rad drain ****. About 1.5 gallons of very clean coolant came out (it took a while). I then finger tightened the drain ****. Since the fluid was so clean, I decided not to flush the system.
I then placed garbage bags and rags under the thermostat housing, and removed the thermostat housing. Very little fluid came out.
I used AC Dexcool (Prestone Dexcool would have done just as well). I made a 1.5 gallon 50/50 mix of the Dexcool with distilled water.
I decided to add this cocktail through the upper rad hose that attaches to the water pump. This forced the air out of the cylinder heads through the bleed hose at the cylinder heads, and allowed me to get the full 1.5 gallons of the new mix back into the engine/rad. Actually I added 1.25 gallons through the rad hose, attached the hose back to the rad, and then dumped the remaining 1/4 gallon into the reservoir. Note that this procedure alleviates the need to warm up the engine to open the thermostat, as coolant is entering on the back side of the thermostat.
I never had to top up the reservoir, even after my 50 mile test run.
My Test Drive
I headed for the 1000 Islands Parkway. Outside temperature was 65 degrees. I observed the 50mph speed limit, all in 6th gear. I was very disappointed to watch the DIC displaying a coolant temperature of 198 degrees, with an occasional blip to 199. With the GM stat, I never saw any temperatures above 198 degrees when in motion.
I drove about 20 miles with no change. I then stopped and idled for a few minutes. The temps started to climb to a high of 216 degrees. I can’t remember ever seeing anything above 212 with the stock thermostat. At this point I was not a happy camper. I started driving immediately, hitting 75 mph. Shortly the temperature dropped to 192 degrees. I then slowed back down to 50 mph, and the temperature went back up to 198 degrees. Disappointing!
My Thoughts
In my humble opinion, the problem here is the lower thermostat plate (reverse poppet) is not seating very well against the inner flange of the water pump. After all, this is not a physically exact replacement thermostat. This was causing my higher temperatures from idle to about 1400 RPM. Once above 1400 RPM, say 75 mph and up, there was enough flow of coolant through the rad to take advantage of the earlier opening thermostat, and hence the 192 degree readings. Note that the temps never dropped below 192 degrees.
I have read several posts in this forum where installing a 180 degree thermostat dropped temps into the 180's. I am envious.
My Solution
I dumped the coolant, went back to the original GM thermostat, and refilled with a new 50/50 mix of Dexcool/distilled water. I repeated my previous test drive. The temperature went to 198 degrees, with an occasional tease of 196 degrees. In other words, as it was before the initial coolant/stat change.
Perhaps in 4 years from now I will endeavor to try all this again, but only if I can find a 180 degree thermostat that is an exact physical match to the GM one. Dream on....
An Additional Note
As part of my research on all this, I sent an email to Callaway, asking if changing to a lower value thermostat would harm the engine or surrounding components, and what thermostat they would recommend for street use. These boys know their stuff.
Here is their response:
My opinion is that changing to a lower thermostat temperature would not "harm" engine components. However, I don't believe it will extend engine life or underhood component life either. Also, the factory engine management system calibration is established using the OEM thermostat setting (not only the fan on and off settings), changing the engine's operating coolant temperature have an effect on exhaust emissions so Callaway does not use or recommend low temperature thermostats.
The 180 degree coolant temperature target is left over from the days of lower pressure coolant systems when drivers had to be concerned about water's boiling point at those lower pressures. Racers had to contend with insufficient radiators for racing applications. As you probably know, they even sold 160 degree thermostats. With modern cooling systems, however, the 210-220 degree coolant temperatures are perfectly fine. Lubricants and clearances used in today's cars and trucks are designed for the present-day stock temperature settings.
Callaway does not install a non-OEM thermostat in any Callaway vehicles. Callaway does not sell low temperature thermostats for do-it-yourself installation either. In your application, I believe it would not be worth the cost and effort to change your stock thermostat.
Thanks for your inquiry. Best regards, Mike Vendetto
Perhaps I should have listened.
Hope this post helps answer some coolant change and thermostat questions.
November 2012
M.....
My Replacement Thermostat
After much internet research, I decided to go with a Lingenfelter 180 degree thermostat. This is in fact a Motorad, which has a good reputation. I tested the thermostat on the stove with an accurate digital thermometer (and candy thermometer). As per spec, it started to open (very slightly) at 180 degrees; at 190 degrees it opened about 2mm (0.08"); and appeared to be fully opened around 199 degrees about 6 mm (0.24"). It appeared to open linearly. Please note these are rough numbers.
My “stovetop” test:
I did a side by side comparison with the stock GM thermostat. The 188 degree GM thermostat is much more rugged and heavier, and IMHO, of a better quality. This is not to knock the Motorad, but it was very apparent when looking at them side by side.
The only markings I found on the GM unit were “NTCL 86 degree C” and what looked like “LDW” on the center shaft.
My concerns with the Motorad were threefold: The GM appeared to be more rugged, the Motorad length plate to plate was slightly longer, and the Motorad lower plate had holes vs the GM one which is a solid disk with slight ridges on the underside.
Comparison Top View GM and Motorad (GM on LHS):
Comparison Side View GM and Motorad (GM on LHS). Note that the GM Plate To Plate distance is slightly shorter.:
Comparison Bottom View GM and Motorad (GM on LHS). Note differences in bottom plates.:
The lower plate (reverse poppet) is what blocks the inner opening in the water pump, ensuring that coolant flows through the rad, and preventing most coolant from circulating back through the block when the thermostat is opened. My thoughts were that the GM one would do a better job at this.
View inside water pump. Note the flange where the lower plate contacts. This is where the coolant recycles back into the block when thermostat is closed. It should be closed by pressure from the lower plate when the thermostat is opened.:
As per their web site, and my discussions with Motorad, there is no exact alternate thermostat for the 2008 C6 LS3 (2009+ use a different stat/housing/water pump). If you want an exact Motorad thermostat for your 2008, the only option is a 188 degree.
I would guess that Linenfelter did his own research and came up with this 180 degree alternative. By the way I am not knocking Motorad or Lingenfelter in any way - I’m just saying.
My Procedure
I opened the reservoir cap and the rad drain ****. About 1.5 gallons of very clean coolant came out (it took a while). I then finger tightened the drain ****. Since the fluid was so clean, I decided not to flush the system.
I then placed garbage bags and rags under the thermostat housing, and removed the thermostat housing. Very little fluid came out.
I used AC Dexcool (Prestone Dexcool would have done just as well). I made a 1.5 gallon 50/50 mix of the Dexcool with distilled water.
I decided to add this cocktail through the upper rad hose that attaches to the water pump. This forced the air out of the cylinder heads through the bleed hose at the cylinder heads, and allowed me to get the full 1.5 gallons of the new mix back into the engine/rad. Actually I added 1.25 gallons through the rad hose, attached the hose back to the rad, and then dumped the remaining 1/4 gallon into the reservoir. Note that this procedure alleviates the need to warm up the engine to open the thermostat, as coolant is entering on the back side of the thermostat.
I never had to top up the reservoir, even after my 50 mile test run.
My Test Drive
I headed for the 1000 Islands Parkway. Outside temperature was 65 degrees. I observed the 50mph speed limit, all in 6th gear. I was very disappointed to watch the DIC displaying a coolant temperature of 198 degrees, with an occasional blip to 199. With the GM stat, I never saw any temperatures above 198 degrees when in motion.
I drove about 20 miles with no change. I then stopped and idled for a few minutes. The temps started to climb to a high of 216 degrees. I can’t remember ever seeing anything above 212 with the stock thermostat. At this point I was not a happy camper. I started driving immediately, hitting 75 mph. Shortly the temperature dropped to 192 degrees. I then slowed back down to 50 mph, and the temperature went back up to 198 degrees. Disappointing!
My Thoughts
In my humble opinion, the problem here is the lower thermostat plate (reverse poppet) is not seating very well against the inner flange of the water pump. After all, this is not a physically exact replacement thermostat. This was causing my higher temperatures from idle to about 1400 RPM. Once above 1400 RPM, say 75 mph and up, there was enough flow of coolant through the rad to take advantage of the earlier opening thermostat, and hence the 192 degree readings. Note that the temps never dropped below 192 degrees.
I have read several posts in this forum where installing a 180 degree thermostat dropped temps into the 180's. I am envious.
My Solution
I dumped the coolant, went back to the original GM thermostat, and refilled with a new 50/50 mix of Dexcool/distilled water. I repeated my previous test drive. The temperature went to 198 degrees, with an occasional tease of 196 degrees. In other words, as it was before the initial coolant/stat change.
Perhaps in 4 years from now I will endeavor to try all this again, but only if I can find a 180 degree thermostat that is an exact physical match to the GM one. Dream on....
An Additional Note
As part of my research on all this, I sent an email to Callaway, asking if changing to a lower value thermostat would harm the engine or surrounding components, and what thermostat they would recommend for street use. These boys know their stuff.
Here is their response:
My opinion is that changing to a lower thermostat temperature would not "harm" engine components. However, I don't believe it will extend engine life or underhood component life either. Also, the factory engine management system calibration is established using the OEM thermostat setting (not only the fan on and off settings), changing the engine's operating coolant temperature have an effect on exhaust emissions so Callaway does not use or recommend low temperature thermostats.
The 180 degree coolant temperature target is left over from the days of lower pressure coolant systems when drivers had to be concerned about water's boiling point at those lower pressures. Racers had to contend with insufficient radiators for racing applications. As you probably know, they even sold 160 degree thermostats. With modern cooling systems, however, the 210-220 degree coolant temperatures are perfectly fine. Lubricants and clearances used in today's cars and trucks are designed for the present-day stock temperature settings.
Callaway does not install a non-OEM thermostat in any Callaway vehicles. Callaway does not sell low temperature thermostats for do-it-yourself installation either. In your application, I believe it would not be worth the cost and effort to change your stock thermostat.
Thanks for your inquiry. Best regards, Mike Vendetto
Perhaps I should have listened.
Hope this post helps answer some coolant change and thermostat questions.
November 2012
M.....
Last edited by Mike Green9; 11-28-2012 at 05:03 PM. Reason: Pics
11-28-2012, 04:57 PM
#2
Team Owner
Member Since: Jun 2005
Location: Northern, VA
Posts: 46,106
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1,944 Posts
St. Jude Donor '15
"In honor of jpee"
quite interesting. one question: was that a stock NEW GM thermostat you re-installed, or the existing one you took out?
11-28-2012, 05:10 PM
#4
Drifting
Thread Starter
I went back to the original GM 4 year old stat that came with the car.
..Why in the world would you want to be in the 180's?...
I wanted to run 190-192. I thought the 8 degree lower Motorad stat would do this. Hard for an "old horse" to learn new tricks, but I'm working on it.
Thanks for the responses,
M....
..Why in the world would you want to be in the 180's?...
I wanted to run 190-192. I thought the 8 degree lower Motorad stat would do this. Hard for an "old horse" to learn new tricks, but I'm working on it.
Thanks for the responses,
M....
11-28-2012, 05:17 PM
#5
Race Director
Hey Mike, thank you for your detailed report. I was considering this, but will leave well enough alone for now. I'm an old guy who has done 160 stats on more hot rods than I care to remember, but the engineering is much more sound these days in this area with all that comes into play.
11-28-2012, 06:10 PM
#6
Safety Car
Member Since: Jan 2009
Location: Mooresville (Race City USA) NC
Posts: 4,681
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Great report; confirms my opinion you keep it stock unless you really know what the heck your doing, and chances are, unless you have an engineering or tech school degree, and experience in the automotive field, you don't. I'm really amazed at your statement the 2009 and newer LS3 engines have a different thermostat, housing and water pump than the 2008 LS3 engine. How did you confirm this extraordinary finding?
11-28-2012, 06:35 PM
#7
Melting Slicks
I recently replaced my 160° Stat installed by a well known vendor in Dallas with a 186° Stat from Stant. The Stant was $13 from the parts store.
A bunch of us in Austin, Texas tested 160° but noticed abnormal temperature swings.
I had a 160° installed 4 years ago and on the highway, my temp got down to 178-180° but then zoomed up to 205°-210° even when cranking the fans up. Oil temps stayed below 200° most of the time, too. That's too cold in my opinion.
You can crank the fan duty cycle up, but this can overheat the fan connector and melt it causing the fans to stop working.
Some of the 160° stats we purchased from reputable vendors did not seem to fully open and cause the coolant temps to go over 230°-240° in stop-n-go traffic.
I really did not like the 20° + swings in temps during normal driving and the oil temp below 200°. You want the any condensation that accumulates in the oil to boil out.
For the old small blocks where coolant was routed throught the intake manifold, a 160° stat kept the intake cooler and make the air denser going into the cylinder. But today's plastic manifolds don't have that.
The water pump, engine, and radiator seem to be designed to balance the temp out in the 198°-205° range and stay there constantly.
I read the comments from Callaway and have to agree 100% based on my personal experience.
Today, with the 186° stat from Stant, my coolant stays all the time in the 198° - 204° range and oil temps stay in the 215° - 225° range all the time. From my research, this is ideal especially in the hot Texas summer.
My car is a 2005 Z51 with full mods including heads, cam, intake, headers, etc....
A bunch of us in Austin, Texas tested 160° but noticed abnormal temperature swings.
I had a 160° installed 4 years ago and on the highway, my temp got down to 178-180° but then zoomed up to 205°-210° even when cranking the fans up. Oil temps stayed below 200° most of the time, too. That's too cold in my opinion.
You can crank the fan duty cycle up, but this can overheat the fan connector and melt it causing the fans to stop working.
Some of the 160° stats we purchased from reputable vendors did not seem to fully open and cause the coolant temps to go over 230°-240° in stop-n-go traffic.
I really did not like the 20° + swings in temps during normal driving and the oil temp below 200°. You want the any condensation that accumulates in the oil to boil out.
For the old small blocks where coolant was routed throught the intake manifold, a 160° stat kept the intake cooler and make the air denser going into the cylinder. But today's plastic manifolds don't have that.
The water pump, engine, and radiator seem to be designed to balance the temp out in the 198°-205° range and stay there constantly.
I read the comments from Callaway and have to agree 100% based on my personal experience.
Today, with the 186° stat from Stant, my coolant stays all the time in the 198° - 204° range and oil temps stay in the 215° - 225° range all the time. From my research, this is ideal especially in the hot Texas summer.
My car is a 2005 Z51 with full mods including heads, cam, intake, headers, etc....
11-28-2012, 06:46 PM
#8
Race Director
I recently replaced my 160° Stat installed by a well known vendor in Dallas with a 186° Stat from Stant. The Stant was $13 from the parts store.
A bunch of us in Austin, Texas tested 160° but noticed abnormal temperature swings.
I had a 160° installed 4 years ago and on the highway, my temp got down to 178-180° but then zoomed up to 205°-210° even when cranking the fans up. Oil temps stayed below 200° most of the time, too. That's too cold in my opinion.
You can crank the fan duty cycle up, but this can overheat the fan connector and melt it causing the fans to stop working.
Some of the 160° stats we purchased from reputable vendors did not seem to fully open and cause the coolant temps to go over 230°-240° in stop-n-go traffic.
I really did not like the 20° + swings in temps during normal driving and the oil temp below 200°. You want the any condensation that accumulates in the oil to boil out.
For the old small blocks where coolant was routed throught the intake manifold, a 160° stat kept the intake cooler and make the air denser going into the cylinder. But today's plastic manifolds don't have that.
The water pump, engine, and radiator seem to be designed to balance the temp out in the 198°-205° range and stay there constantly.
I read the comments from Callaway and have to agree 100% based on my personal experience.
Today, with the 186° stat from Stant, my coolant stays all the time in the 198° - 204° range and oil temps stay in the 215° - 225° range all the time. From my research, this is ideal especially in the hot Texas summer.
My car is a 2005 Z51 with full mods including heads, cam, intake, headers, etc....
A bunch of us in Austin, Texas tested 160° but noticed abnormal temperature swings.
I had a 160° installed 4 years ago and on the highway, my temp got down to 178-180° but then zoomed up to 205°-210° even when cranking the fans up. Oil temps stayed below 200° most of the time, too. That's too cold in my opinion.
You can crank the fan duty cycle up, but this can overheat the fan connector and melt it causing the fans to stop working.
Some of the 160° stats we purchased from reputable vendors did not seem to fully open and cause the coolant temps to go over 230°-240° in stop-n-go traffic.
I really did not like the 20° + swings in temps during normal driving and the oil temp below 200°. You want the any condensation that accumulates in the oil to boil out.
For the old small blocks where coolant was routed throught the intake manifold, a 160° stat kept the intake cooler and make the air denser going into the cylinder. But today's plastic manifolds don't have that.
The water pump, engine, and radiator seem to be designed to balance the temp out in the 198°-205° range and stay there constantly.
I read the comments from Callaway and have to agree 100% based on my personal experience.
Today, with the 186° stat from Stant, my coolant stays all the time in the 198° - 204° range and oil temps stay in the 215° - 225° range all the time. From my research, this is ideal especially in the hot Texas summer.
My car is a 2005 Z51 with full mods including heads, cam, intake, headers, etc....
11-28-2012, 06:58 PM
#9
Melting Slicks
Still, 216° is perfectly OK.
You can increase the fan duty cycle a little but don't crank it up to 90% accross the whole range like some guys do. That's a failure waiting to happen.
11-28-2012, 07:09 PM
#10
very interesting
11-28-2012, 07:33 PM
#11
Melting Slicks
I'd love to see CoW chime in on this thread. He's still a 160deg insistent tuner. I love my lower oil temps since my tune. It's been cool up here since my tune so I have to wait for spring/summer to see actual results. Interesting....
11-29-2012, 01:59 PM
#12
Drifting
Thread Starter
For 2005-2008 LS2 & LS3 (LS7 ??):
2.12 upper outer diameter (without gasket) (54mm)
2.28 upper outer diameter (with gasket)
1.46 lower outer diameter
1.80 disk to disk length
2.57 overall length
For the 2009+ LS3 (LS7 & LS9 ????)
2.20 upper outer diameter (without gasket) (57mm)
2.34 upper outer diameter (with gasket)
1.59 lower outer diameter
1.91 disk to disk length
2.71 overall length
If changing to a 2009+ thermostat, you would have to change the thermostat housing as well. Since the plate to plate (disk to disk) length is .11" longer, AND the lower plate diameter is .13" bigger in the revised thermostat, the water pump should be changed as well, since the inner flange depth and diameter for coolant flow back through the heads would be different. If I had to change my water pump, I would consider updating to the 2009+ pump/stat/housing package.
I have heard stories about the fan connector melting. The fan can pull as much as 60 amps if running at 90%. I would not recommend the fan to be on at 90% below engine coolant temps of 212. By the way, GM puts the fan on when Engine coolant hits:
204 (Lo speed 15%)
235 (Hi speed 90%)
GM considers the LS3 is too hot at 256 degrees, and will deactivate the fuel injectors to 4 cylinders. A 4 Cylinder Vette - YIKES
.On that note, I'm out'a'here...
M......
11-29-2012, 02:37 PM
#13
Pro
You can change the thermostats all day long and the temp. will continue to climb until the fan kicks on to lower it. You have to re-program the computer to have the fan come on at a lower temp. Problem solved!!!
11-29-2012, 03:10 PM
#14
Le Mans Master
I admit I am a bit behind technology wise, but I was most unhappy when I ran my old supercharged L98 with a 160 stat. When it was 40 or below, the heater NEVER made enough heat to warm up the cabin. After a bunch of experimentation, 180 seemed to make it run the best. But you have to have the ECM match the fan settings like the above poster said, or it won't be right.
I think Gooberment Motors installs 190 to please the their EPA brothers.
I think Gooberment Motors installs 190 to please the their EPA brothers.