Thermostat Temperature Secrecy
Thread Starter
Intermediate
Joined: Feb 2008
Posts: 44
Likes: 3
From: Oklahoma City Oklahoma
Why Did GM Change Thermostat Temperature in 2005?
Maybe this issue has been addressed elsewhere, but I have been unable to find specific OEM thermostat TEMPERATURE information associated with the 2005 model-year in the C6 forum.
Recently I replaced the water pump on my 2005 Z51. The GM pump # 89018052 came with a 195 degree thermostat and stat housing installed on the pump (see photo below). At the time I failed to consider that the new pump might have a different temperature thermostat than what came with the car, thus I installed the pump as it came out of the box. Eventually I discovered that the 2005 Corvette originally had a 187 degree (86C) stat that was superseded by the 195 degree stat - and the 187 degree stat is no longer available through GM Corvette parts listings. Unknowingly, by replacing the water pump I replaced a 187 degree stat with a 195 degree stat. It is likely a number of forum members have replaced water pumps not knowing they were also installing hotter thermostats that were already bolted to the new pump. Oddly, my local Chevrolet dealer said the water pump was listed WITHOUT the thermostat and stat housing. He seemed surprised that my pump was packaged with a thermostat and housing installed.
I've read countless threads on cooling issues with C6 thermostats, but have been unable to ascertain WHY GM went from a 187 degree thermostat in 2005 to a 195 degree thermostat. Some credible sources tell me not to worry about the car running 10 to 20 degrees hotter than it ran with the old 187 degree thermostat. However, it is a simple task to change out the thermostat – aside from the slow refill procedure required to get all of the air out of a C6 cooling system.
What troubles me is that the car seldom exceeded 195 to 203 degrees with the original 187 (86C) thermostat. Occasionally in the heat and humidity of Oklahoma and Texas I would see 207 degrees in gridlock traffic, but I know it will now run far hotter in the heat of summer with the new 195 degree thermostat. I am presently running 210 F to 215 F with the 195 degree thermostat with 32 F degree outside air. The obvious and easy solution is to replace the new 195 degree stat with a 180 or 187 degree thermostat, but I’m a gearhead who likes to know WHY the design change was made.
Two questions:
1) Why did Chevrolet supersede the 187 degree thermostat with a 195 degree thermostat in the 2005 model year?
2) Does anyone besides me feel that 210 F to 215 F on the DIC is too hot with 34 degree outside air in light traffic?
My best guess is that it has to do with emissions updates or perhaps inventory costs savings. Typically, Corvette design engineers put a lot of data and thought into the design thermostat temperature operating range for each specific Corvette model-year. Thus I am puzzled as to the apparent secrecy and non-published temperature ratings of General Motors AC Delco thermostats for the 2005 Corvette.
I am hoping some forum members have long ago sorted through this thermostat temperature-design change mystery, and I would be grateful for some insight regarding why GM went to higher temperatures on replacement thermostats on the 2005 Z51.
Recently I replaced the water pump on my 2005 Z51. The GM pump # 89018052 came with a 195 degree thermostat and stat housing installed on the pump (see photo below). At the time I failed to consider that the new pump might have a different temperature thermostat than what came with the car, thus I installed the pump as it came out of the box. Eventually I discovered that the 2005 Corvette originally had a 187 degree (86C) stat that was superseded by the 195 degree stat - and the 187 degree stat is no longer available through GM Corvette parts listings. Unknowingly, by replacing the water pump I replaced a 187 degree stat with a 195 degree stat. It is likely a number of forum members have replaced water pumps not knowing they were also installing hotter thermostats that were already bolted to the new pump. Oddly, my local Chevrolet dealer said the water pump was listed WITHOUT the thermostat and stat housing. He seemed surprised that my pump was packaged with a thermostat and housing installed.
I've read countless threads on cooling issues with C6 thermostats, but have been unable to ascertain WHY GM went from a 187 degree thermostat in 2005 to a 195 degree thermostat. Some credible sources tell me not to worry about the car running 10 to 20 degrees hotter than it ran with the old 187 degree thermostat. However, it is a simple task to change out the thermostat – aside from the slow refill procedure required to get all of the air out of a C6 cooling system.
What troubles me is that the car seldom exceeded 195 to 203 degrees with the original 187 (86C) thermostat. Occasionally in the heat and humidity of Oklahoma and Texas I would see 207 degrees in gridlock traffic, but I know it will now run far hotter in the heat of summer with the new 195 degree thermostat. I am presently running 210 F to 215 F with the 195 degree thermostat with 32 F degree outside air. The obvious and easy solution is to replace the new 195 degree stat with a 180 or 187 degree thermostat, but I’m a gearhead who likes to know WHY the design change was made.
Two questions:
1) Why did Chevrolet supersede the 187 degree thermostat with a 195 degree thermostat in the 2005 model year?
2) Does anyone besides me feel that 210 F to 215 F on the DIC is too hot with 34 degree outside air in light traffic?
My best guess is that it has to do with emissions updates or perhaps inventory costs savings. Typically, Corvette design engineers put a lot of data and thought into the design thermostat temperature operating range for each specific Corvette model-year. Thus I am puzzled as to the apparent secrecy and non-published temperature ratings of General Motors AC Delco thermostats for the 2005 Corvette.
I am hoping some forum members have long ago sorted through this thermostat temperature-design change mystery, and I would be grateful for some insight regarding why GM went to higher temperatures on replacement thermostats on the 2005 Z51.
Last edited by Doppler1992; Feb 13, 2011 at 02:56 PM. Reason: Clarification
Thread Starter
Intermediate
Joined: Feb 2008
Posts: 44
Likes: 3
From: Oklahoma City Oklahoma
Gates Thermoplastic PermaGrip Hose Clamps
I am considering trying the Gates Thermoplastic PermaGrip hose clamps on the hoses involved with the thermostat and water pump replacement associated with my previous post, and would like to hear (good or bad) from folks who have used the Gates PermaGrip product. The “memory” concept of these heat shrink band-clamps makes sense to me. In addition, there is far greater width of clamping surface that also conforms to the bead on the hose nipple compared to a half-inch wide worm drive clamp.
Anyone have any personal experience with these clamps? http://www.gates.com/brochure.cfm?br...ocation_id=546
Anyone have any personal experience with these clamps? http://www.gates.com/brochure.cfm?br...ocation_id=546
Melting Slicks
Joined: Mar 2007
Posts: 2,391
Likes: 23
From: Santa Barbara CA
Why not just get a quality aftermarket 180 degree t-stat like this? : http://www.lingenfelter.com/mm5/merc...Category_Code=
Should put your cooling system close to the way it was before. I'd rather buy from a reputable performance company than take my chances with an Autozone/Pep boys mystery part.
Keep in mind that the stock 195 thermostat that comes in all the current cars starts to open at 195 degrees. This means it will probably run close to 200+ at all times after warm-up. If you want the engine to run below that temp, you will need to change the thermostat.
I'm not sure why GM made the change ( probably emissions related), but it is what it is. I'd buy a quality 160 or 180 degree replacement before I put the original one back in.
Should put your cooling system close to the way it was before. I'd rather buy from a reputable performance company than take my chances with an Autozone/Pep boys mystery part.
Keep in mind that the stock 195 thermostat that comes in all the current cars starts to open at 195 degrees. This means it will probably run close to 200+ at all times after warm-up. If you want the engine to run below that temp, you will need to change the thermostat.
I'm not sure why GM made the change ( probably emissions related), but it is what it is. I'd buy a quality 160 or 180 degree replacement before I put the original one back in.
Thread Starter
Intermediate
Joined: Feb 2008
Posts: 44
Likes: 3
From: Oklahoma City Oklahoma
Thanks to Streetk14 for the Lingenfelter link. I did not realize they had a line on small aftermarket parts like thermostats.
When I mentioned AutoZone I was using that statement more or less as a figure of speech - telling myself that I'd look for a Stant or Gates thermostat if the vote was to NOT reinstall the original thermostat. I wonder who makes thermostats for Lingenfelter?
I concur any thermostat from AutoZone would likely be a "mystery part."
When I mentioned AutoZone I was using that statement more or less as a figure of speech - telling myself that I'd look for a Stant or Gates thermostat if the vote was to NOT reinstall the original thermostat. I wonder who makes thermostats for Lingenfelter?
I concur any thermostat from AutoZone would likely be a "mystery part."
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Why not just get a quality aftermarket 180 degree t-stat like this? : http://www.lingenfelter.com/mm5/merc...Category_Code=
Should put your cooling system close to the way it was before. I'd rather buy from a reputable performance company than take my chances with an Autozone/Pep boys mystery part.
Keep in mind that the stock 195 thermostat that comes in all the current cars starts to open at 195 degrees. This means it will probably run close to 200+ at all times after warm-up. If you want the engine to run below that temp, you will need to change the thermostat.
I'm not sure why GM made the change ( probably emissions related), but it is what it is. I'd buy a quality 160 or 180 degree replacement before I put the original one back in.
Should put your cooling system close to the way it was before. I'd rather buy from a reputable performance company than take my chances with an Autozone/Pep boys mystery part.
Keep in mind that the stock 195 thermostat that comes in all the current cars starts to open at 195 degrees. This means it will probably run close to 200+ at all times after warm-up. If you want the engine to run below that temp, you will need to change the thermostat.
I'm not sure why GM made the change ( probably emissions related), but it is what it is. I'd buy a quality 160 or 180 degree replacement before I put the original one back in.
BC
Melting Slicks
Joined: Oct 2010
Posts: 2,314
Likes: 4
From: Cape May, NJ; Guntersville, AL; Orange Beach, AL
I think the tstat being changed by 7 degrees is a non issues. GM engineers prob. did studies that showed the engine more effiecient with a small change in temp. Nothing to worry about or put any thought into if you ask me. I still don't understand why some change to a 160 stat. I think that companies like LPE and Callaway know more than about anyone in the business but I don't understand why you would change the engine temp. To me it wouldn't run in the optimal range that it was engineered for.
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Thread Starter
Intermediate
Joined: Feb 2008
Posts: 44
Likes: 3
From: Oklahoma City Oklahoma
A follow-up on my last post. Previously I stated my new GM water pump came with a 195 F degree thermostat. That was incorrect. After removing the new thermostat for inspection, I discovered the new pump had an 86C (187F) thermostat which is the same temperature thermostat as the 2005 factory installed thermostat.
I reinstalled the old thermostat and now the car runs at 195F to 205F as it has run since it was brand new. With the new thermostat that came with the pump, the car ran at 205F to 215F so I am clueless as to why the operating temperature difference since both stats are stamped 86C (187F) degrees.
I performed a liquid boil test on both thermostats in glycol as outlined in the Corvette service manual, and could see no difference in open and close temperatures - so it is puzzling as to why the newer stat makes the car run hotter. The old 2005 stat had holes in the spring-loaded plate, whereas the new stat does NOT have the holes. Aside from that minor physical difference, I see no reason the two stats would function differently.
UPDATE: Eventually I figured out that I changed the water pump and thermostat in February 2011 during cold weather. The Corvette will often run HOTTER in cold weather (in urban traffic) because the electric fans do not run as often as they would run in hot humid Oklahoma summer weather, and the electric condenser fan for the HAVC would rarely run during cold weather. Thus, a Corvette would likely operate at slightly higher coolant temperatures during cold weather because the computer does not call for the radiator and condenser fans as often. A simple explanation that I should have quickly figured out in 2011.
I reinstalled the old thermostat and now the car runs at 195F to 205F as it has run since it was brand new. With the new thermostat that came with the pump, the car ran at 205F to 215F so I am clueless as to why the operating temperature difference since both stats are stamped 86C (187F) degrees.
I performed a liquid boil test on both thermostats in glycol as outlined in the Corvette service manual, and could see no difference in open and close temperatures - so it is puzzling as to why the newer stat makes the car run hotter. The old 2005 stat had holes in the spring-loaded plate, whereas the new stat does NOT have the holes. Aside from that minor physical difference, I see no reason the two stats would function differently.
UPDATE: Eventually I figured out that I changed the water pump and thermostat in February 2011 during cold weather. The Corvette will often run HOTTER in cold weather (in urban traffic) because the electric fans do not run as often as they would run in hot humid Oklahoma summer weather, and the electric condenser fan for the HAVC would rarely run during cold weather. Thus, a Corvette would likely operate at slightly higher coolant temperatures during cold weather because the computer does not call for the radiator and condenser fans as often. A simple explanation that I should have quickly figured out in 2011.
Last edited by Doppler1992; Feb 12, 2016 at 06:05 AM. Reason: New Information
