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How do you even know if the gauge is accurate? I just went through this – car wasn’t displaying any signs of overheating but I notice the temp gauge has been reading 210*. I happen to have an IR thermometer and it says 180* at the thermostat housing & upper rad hose.
Just a base check before you go down the rabbit hole
Important thing to know about IR Temp devices. They are accurate reading from the color black surfaces. Measuring the hose may be a few degrees cooler than the actual coolant.
To see how accurate your gun is , boil a pot of water a measure its temp. should be ~ 212 degrees F. or 100 Degrees C.
So if you measure your hoses at get 212 degrees you know the coolant will be a few degrees hotter yet and at the boiling point of water. The antifreeze is the only thing that prevents a coolant boil over.
Important thing when you measure the upper vs lower rad hose is to note the difference in temp. This will show how well the radiator is working.
Last edited by cagotzmann; 08-15-2017 at 09:01 PM.
I have a stock 77' with L-82 and A/C. Using a 180 degree thermostat, my car runs about 190. If I have the A/C on it tops maybe 200. Even on the hottest days of the year, even in traffic.
I put an accurate temp gauge in that exact same location a couple of months ago.
Originally Posted by Wee
You might want to add a mechanical temp gauge as a double check....My 72 was showing around 220 highway so I added another gauge and it read right at 190 when the stock gauge was at 220. Checked with a IR temp gun and it confirmed the new gauge was correct. I did as the instructions with the new gauge suggested double check it with a pot of boiling water. Here where I installed the additional gauge.
Further Information : Today I purchased a Klien IR Thermo Gun and will check Upper & Lower Hoses. Also, I was considering the purchase of a stage 2 Stewart Aluminum water pump. Will this reduce the Higher Temp reading ? Any Suggestions or further input in appreciated ? Question : Will this aluminum water pump tend to leak if the car is only driven in Nice weather and not year around ? It is stored during the winter.
Important thing to know about IR Temp devices. They are accurate reading from the color black surfaces. Measuring the hose may be a few degrees cooler than the actual coolant.
To see how accurate your gun is , boil a pot of water a measure its temp. should be ~ 212 degrees F. or 100 Degrees C.
So if you measure your hoses at get 212 degrees you know the coolant will be a few degrees hotter yet and at the boiling point of water. The antifreeze is the only thing that prevents a coolant boil over.
Important thing when you measure the upper vs lower rad hose is to note the difference in temp. This will show how well the radiator is working.
Further Information : Today I purchased a Klien IR Thermo Gun and will check Upper & Lower Hoses. Also, I was considering the purchase of a stage 2 Stewart Aluminum water pump. Will this reduce the Higher Temp reading ? Any Suggestions or further input in appreciated ? Question : Will this aluminum water pump tend to leak if the car is only driven in Nice weather and not year around ? It is stored during the winter.
First question is the engine an L-82 or base engine L-48?
Assuming everything mentioned is correct and up to standards, The late 70's L-82's ran VERY hot from the factory when brand new, mostly due to emissions, the 882 factory cylinder heads which restrict coolant flow to aid in running the heads hot for more complete combustion, and poor ignition timing. My 100% stock 78 L-82 4 speed when new ran 225 normally and 235-240 with the AC on during hot days AND got hotter on the highway than idle when it was new. Same scenario with my friends brand new 79 L-82 4 speed back in 1979. In fact, GM changed the 12 o'clock position on the temp gauge in 1979 to 220 degrees from 200 degrees to quell customer complaints about the high temps. 79 L-82's with heavy duty cooling added an auxiliary electric fan inside the mechanical fan shroud in 1979 to reduce the temps some...it was a big problem!
The solution is the following:
1. Aluminum radiator
2. 180 degree thermostat
3. Stewart Stage 2 aluminum high flow water pump
4. 1979 Spoiler extension-See below-cars with heavy duty cooling had this extended spoiler for additional cooling
My rebuilt/upgraded 355 L-82 450 Gross HP never gets hotter than 180 degrees regardless of the temp outside, how hard I drive, highway driving etc............
Further Information : Today I purchased a Klien IR Thermo Gun and will check Upper & Lower Hoses. Also, I was considering the purchase of a stage 2 Stewart Aluminum water pump AND HI PRO 180 Thermostat. Will this reduce the Higher Temp reading ? Any Suggestions or further input in appreciated ? Question : Will this aluminum water pump tend to leak if the car is only driven in Nice weather and not year around ? It is stored during the winter.
I'd check temp with the gun before I bought anything else...220 on the gauge may only really be 200 or so with the temp gun....Maybe someone else can chime in on what an acceptable temp on the top hose should be....?
How do you even know if the gauge is accurate? I just went through this – car wasn’t displaying any signs of overheating but I notice the temp gauge has been reading 210*. I happen to have an IR thermometer and it says 180* at the thermostat housing & upper rad hose.
Just a base check before you go down the rabbit hole
Same for me gauge shows 210 IR gun shows 190. Std sender. Also, sender was originally in the block but now in the inlet manifold this change made it read higher also.
Further Information : Today I purchased a Klien IR Thermo Gun and will check Upper & Lower Hoses. Also, I was considering the purchase of a stage 2 Stewart Aluminum water pump AND HI PRO 180 Thermostat. Will this reduce the Higher Temp reading ? Any Suggestions or further input in appreciated ? Question : Will this aluminum water pump tend to leak if the car is only driven in Nice weather and not year around ? It is stored during the winter.
Thanks ... Dee
To answer your question, the Stewart 2 stage aluminum water pump is probably one of the best ones out there! My car sits 99.9% of the time and that water pump has been on my car for at least 10 years now. When I rebuilt/upgraded the OEM L-82 355 in 2014, the stewart water pump was one of the few items that I transferred to the new engine along with the dewitts aluminum radiator and both do a fantastic job cooling the 450 Gross HP engine now with little effort (my coolant temp is 180 no matter the driving style, idle/highway, or temp outside).
To be honest the aluminum radiator and spoiler extension are probably more impactful on keeping the engine cool than the high flow stewart water pump (just extra insurance and weight savings). The aluminum radiator has MUCH more cooling capacity than the brass/copper OEM radiator. The best temp with an OEM L-82 and stock cooling system is around 200 degrees (Note this range is for the L-82 ONLY, the L-48 which are a standard passenger car engine did not have the same high temp issue, only the L-82's). If you want the engine to run in the 175-180 range with no worries of temp creep, you will need to make some changes.
I also have the Stewart stage 2 pump. Excellent product. The only thing you need to know if you buy one is it doesn't have a bypass. Therefore, you need to buy a thermostat with holes drilled in its housing to prevent cavitation of the impeller or drill 3/16" holes in your current thermostat. I store my car every winter for 5-6 months. No pump leaks. I have my original recored rad and zero cooling problems. I've never seen the gauge over 200*.
To answer your question, the Stewart 2 stage aluminum water pump is probably one of the best ones out there! My car sits 99.9% of the time and that water pump has been on my car for at least 10 years now. When I rebuilt/upgraded the OEM L-82 355 in 2014, the stewart water pump was one of the few items that I transferred to the new engine along with the dewitts aluminum radiator and both do a fantastic job cooling the 450 Gross HP engine now with little effort (my coolant temp is 180 no matter the driving style, idle/highway, or temp outside).
To be honest the aluminum radiator and spoiler extension are probably more impactful on keeping the engine cool than the high flow stewart water pump (just extra insurance and weight savings). The aluminum radiator has MUCH more cooling capacity than the brass/copper OEM radiator. The best temp with an OEM L-82 and stock cooling system is around 200 degrees (Note this range is for the L-82 ONLY, the L-48 which are a standard passenger car engine did not have the same high temp issue, only the L-82's). If you want the engine to run in the 175-180 range with no worries of temp creep, you will need to make some changes.
Thank you for your knowledge and help. Is the Pace car spoiler air dam extension a consideration for my "77" C3 ? Will that make a significant difference ? If so, do you have any inclination of degree difference?
I also have the Stewart stage 2 pump. Excellent product. The only thing you need to know if you buy one is it doesn't have a bypass. Therefore, you need to buy a thermostat with holes drilled in its housing to prevent cavitation of the impeller or drill 3/16" holes in your current thermostat. I store my car every winter for 5-6 months. No pump leaks. I have my original recored rad and zero cooling problems. I've never seen the gauge over 200*.
Thank you for your reply. Do you know if the Stewart Hi Pro 301 180 Degree Thermo has this hole already drilled in it ? I am not sure, but it looks as though it does ...
I also have the Stewart stage 2 pump. Excellent product. The only thing you need to know if you buy one is it doesn't have a bypass. Therefore, you need to buy a thermostat with holes drilled in its housing to prevent cavitation of the impeller or drill 3/16" holes in your current thermostat. I store my car every winter for 5-6 months. No pump leaks. I have my original recored rad and zero cooling problems. I've never seen the gauge over 200*.
Great info ... Thank you. I also had my original radiator re~cored a few years back. So, after I check the upper and lower hoses with the IR Gun, I will probably change out the water pump with the Stage 2 Stewart and the 301 180 Degree Thermostat ... do you know if that particular stat has this hole already drilled in it ? It looks as though it does, but I am not sure. I called Stewart Manufacture, but they are in the process of moving their plant ... hard to reach at this time.
Just a clarification, the spoiler extension in my picture in post #26 is NOT the pace car spoiler but a rubber piece that attaches to the Stock GM chin spoiler on 1979 C3 with the L-82 and heavy duty cooling and I purchased from GM in 1990 and put on my 78 L-82. I believe that Wilcox sells a reproduction rubber chin spoiler extension for the 1979 C3 and yes you should be able to use it on your 77...
As for the Robertshaw specially modified thermostat, Resdoggie is correct that it has the 3 holes drilled in the cone tower of the thermostat for the by pass effect needed with the Stewart water pump. I just this year abandoned the modified Robertshaw 3 hole thermostat and reused my regular Robertshaw thermostat that I have had for many year but drilled only 1 hole, not 3 holes. The 3 holes allowed too much coolant to flow pass the thermostat and my engine had difficulty ever getting to full operating temp except on 90 degree days...works perfect now.
Just a clarification, the spoiler extension in my picture in post #26 is NOT the pace car spoiler but a rubber piece that attaches to the Stock GM chin spoiler on 1979 C3 with the L-82 and heavy duty cooling and I purchased from GM in 1990 and put on my 78 L-82. I believe that Wilcox sells a reproduction rubber chin spoiler extension for the 1979 C3 and yes you should be able to use it on your 77...
As for the Robertshaw specially modified thermostat, Resdoggie is correct that it has the 3 holes drilled in the cone tower of the thermostat for the by pass effect needed with the Stewart water pump. I just this year abandoned the modified Robertshaw 3 hole thermostat and reused my regular Robertshaw thermostat that I have had for many year but drilled only 1 hole, not 3 holes. The 3 holes allowed too much coolant to flow pass the thermostat and my engine had difficulty ever getting to full operating temp except on 90 degree days...works perfect now.
No easy solution here ... It seems as though I am gathering the following steps : 1) Check Hoses with IR Gun and also check the integrity of the hoses (New in past 3 years ... very little wear) ( Do you have any idea of what the Lower & Upper should read ... Approximate Temp Range ?
2.) If still registering Hot ... change out the water pump & thermostat 3.) Possible change of air deflector
Also, what was your temp reading before the changeover from 3 holes back to 1 ?
With a good condition radiator and a 180 degree thermostat I would think at highway speeds even at 80 degrees 200 plus would be high.
My LS1 swap in my 71 with a dual pass radiator running a 160 degree thermostat struggles to get to 180 degrees at highway speeds even at 80 degrees.
Your temps seem high to me.
You're not doing your motor any good by running it that cold. The factory uses higher temp thermostats because their highly paid professional engineers understand that temps must be higher to burn off acids and other contaminants in the engine oil.
Last edited by techinspector1; 08-19-2017 at 02:36 AM.
Prior to 1975 most GM cars ran about 180-185 including C3 corvettes. The numbers leapt for coolant temps in the mid to late 70's, especially starting in 1978 due to the increasing difficulty in meeting more difficult emission's standards. High operating temps are needed primarily to allow more complete combustion of the natural pollutants from an internal combustion engine, especially the cat.
As for burning off the oil contaminants, this topic has been debated ad naseum, but I was just out with my 10 C6Z06 last night, and the oil temp stays consistently at 175 degrees at 80 mph. Last time I looked, you need at least 212 oil temp to burn off water vapor and contaminants. In addition, my 78 C3 has an 81-82 oil temp gauge in the clock cluster spot now for 30 years and it oil temp is consistently 175 degrees as well, regardless of the thermostat rating.
I guess the GM engineers did not know what they were doing prior to 1975.....................
Lot's of different opinions on LS operating temps.
When it's in traffic the temp reaches 180-190 degrees, more than enough to burn off any oil gas residue. Never driven in cold weather.
Just a quick thought in regards to the original post. I helped a friend replace the radiator on his C5. I was surprised how plugged the AC condenser was after 200,000 miles.
I purchased a Klein IR 5 Thermo Gun ... Here are some results :
1.) Outdoor Ambient Temp : 82 degrees 2. ) Driving around town 30 to 55 mph 1/2 hour or so ... 3. ) A/C unit on ... Reading 73 Degrees ( Is this Cool enough Temp for A/C and operating in Normal Range ? ) 4. ) Temp Guage while driving : 190 degrees
5.) Parked car running readings as follows : 200 on factory guage 6.) Upper Hose : 190 degrees 6.) Lower Hose : 173 degrees ... This seems in proper operating range for around town (? ) Highway may be a different story ...
Question : Is the Top Radiator Hose the more accurate measurement and are these readings accurate to the guage reading ? Meaning the top hose 190 # and the factory guage reading : 200 Degrees ? Also, as recommended : I adjusted the Emissivity Meter reading to 0.94 for hard rubber ... Important Note : These adjustments for different compounds make a Big Difference in readings ... up to 10 Degrees or so.
Prior to 1975 most GM cars ran about 180-185 including C3 corvettes. The numbers leapt for coolant temps in the mid to late 70's, especially starting in 1978 due to the increasing difficulty in meeting more difficult emission's standards. High operating temps are needed primarily to allow more complete combustion of the natural pollutants from an internal combustion engine, especially the cat.
As for burning off the oil contaminants, this topic has been debated ad naseum, but I was just out with my 10 C6Z06 last night, and the oil temp stays consistently at 175 degrees at 80 mph. Last time I looked, you need at least 212 oil temp to burn off water vapor and contaminants. In addition, my 78 C3 has an 81-82 oil temp gauge in the clock cluster spot now for 30 years and it oil temp is consistently 175 degrees as well, regardless of the thermostat rating.
I guess the GM engineers did not know what they were doing prior to 1975.....................
Greetings Valued Corvette Members !
Quick Update :
I purchased a Klein IR 5 Thermo Gun ... Here are some results :
1.) Outdoor Ambient Temp : 82 degrees 2. ) Driving around town 30 to 55 mph 1/2 hour or so ... 3. ) A/C unit on ... Reading 73 Degrees ( Is this Cool enough Temp for A/C and operating in Normal Range ? ) 4. ) Temp Guage while driving : 190 degrees
5.) Parked car running readings as follows : 200 on factory guage 6.) Upper Hose : 190 degrees 6.) Lower Hose : 173 degrees ... This seems in proper operating range for around town (? ) Highway may be a different story ...
Question : Is the Top Radiator Hose the more accurate measurement and are these readings accurate to the guage reading ? Meaning the top hose 190 # and the factory guage reading : 200 Degrees ? Also, as recommended : I adjusted the Emissivity Meter reading to 0.94 for hard rubber ... Important Note : These adjustments for different compounds make a Big Difference in readings ... up to 10 Degrees or so.
08-15-2017, 09:01 PM
