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Hummer H3For the Hummer driver who wants the rugged look and off road capabilities of the Hummer, but in a smaller size and with a more fuel economy friendly engine.
220-225 is what I am running today, its 110F out. This is just cruising around.
Checked my AC levels as it's suggested that low or overcharged AC can cause extra heat at the condenser coil thus adding more heat to the air flow. AC levels checked out 55PSI R134. Radiator was recently replaced along with a thermostat for this exact reason "car running too hot". Today replaced belt, belt tensioner, and pulley with OEM. Fan Clutch looks fine. Checked for blown or leaky head gasket with a block tester, also checks out.
I don't understand how some suggest that the NEW OE thermostat is 5 degrees hotter than before and this is why we're seeing higher than normal operating temps. At 220-225 a 190 or 195 Tstat is wide open... that doesn't seem right. Furthermore, 225F is considered critical temperature, anything over is overheating per Cooling Troubleshooting Guide. So why are so many people on here say that 220-225 is normal???
220-225 is what I am running today, its 110F out. This is just cruising around.
Checked my AC levels as it's suggested that low or overcharged AC can cause extra heat at the condenser coil thus adding more heat to the air flow. AC levels checked out 55PSI R134. Radiator was recently replaced along with a thermostat for this exact reason "car running too hot". Today replaced belt, belt tensioner, and pulley with OEM. Fan Clutch looks fine. Checked for blown or leaky head gasket with a block tester, also checks out.
I don't understand how some suggest that the NEW OE thermostat is 5 degrees hotter than before and this is why we're seeing higher than normal operating temps. At 220-225 a 190 or 195 Tstat is wide open... that doesn't seem right. Furthermore, 225F is considered critical temperature, anything over is overheating per Cooling Troubleshooting Guide. So why are so many people on here say that 220-225 is normal???
Not gonna lie, that thought crossed my mind. But why?
As I learn a little more about this car/engine, I realized that the cooling system is a bit weird. The T-Stat is at the engine inlet after the radiator, so it gets cooler refrigerant flowing through it and I suspect doesn't fully open until internal engine temps are way too hot. Apart from the stupid location it's all starting to make sense to me. In warmer climates, 190degree T-stat where its located just doesn't cut it, so I gutted that sucker. Went for a drive, same route as yesterday and its much better, highest I gotten was 215F, still warmer than I'd like. I want to stay between 190-210 if possible. Meanwhile I ordered an inline 180 degree t-stat that I will install at the upper radiator hose and call it a day..
Funny how the solution to a cooling problem is to over engineer coolant so it doesn't boil until 265f at 15psi instead of doing it right the first time.
Not gonna lie, that thought crossed my mind. But why?
As I learn a little more about this car/engine, I realized that the cooling system is a bit weird. The T-Stat is at the engine inlet after the radiator, so it gets cooler refrigerant flowing through it and I suspect doesn't fully open until internal engine temps are way too hot. Apart from the stupid location it's all starting to make sense to me. In warmer climates, 190degree T-stat where its located just doesn't cut it, so I gutted that sucker. Went for a drive, same route as yesterday and its much better, highest I gotten was 215F, still warmer than I'd like. I want to stay between 190-210 if possible. Meanwhile I ordered an inline 180 degree t-stat that I will install at the upper radiator hose and call it a day..
Funny how the solution to a cooling problem is to over engineer coolant so it doesn't boil until 265f at 15psi instead of doing it right the first time.
The OEM T-stat is perfectly mounted in a hot spot & opens/closes perfectly for my 3 after 16+yrs!
Not gonna lie, that thought crossed my mind. But why?
As I learn a little more about this car/engine, I realized that the cooling system is a bit weird. The T-Stat is at the engine inlet after the radiator, so it gets cooler refrigerant flowing through it and I suspect doesn't fully open until internal engine temps are way too hot. Apart from the stupid location it's all starting to make sense to me. In warmer climates, 190degree T-stat where its located just doesn't cut it, so I gutted that sucker. Went for a drive, same route as yesterday and its much better, highest I gotten was 215F, still warmer than I'd like. I want to stay between 190-210 if possible. Meanwhile I ordered an inline 180 degree t-stat that I will install at the upper radiator hose and call it a day..
Funny how the solution to a cooling problem is to over engineer coolant so it doesn't boil until 265f at 15psi instead of doing it right the first time.
everything is right! that's exactly what I did. I moved the thermostat to the top and got rid of overheating. Anyone who says that the temperature is above the middle is the norm, he is wrong.
3/4 on the Gauge is, in fact, NORMAL. The gauge is like an idiot light with a needle, it is not providing you the actual temp of the coolant. One H3 might be at 3/4 on the dash gauge and actually have coolant temp at 200F, the next one can be half way and also have actual coolant temp at 200F. I would not get your panties all in a wad over what the gauge is showing unless you see the actual temp on a scanner.
H3s are SUPPOSED TO RUN in a set range! They are designed that way on purpose to be around 195-215F. Why??? Look it up. Emissions efficiency. Look up the TSBs on the topic, then after you have read those and have the information that GM provided its service techs to respond to this very situation, come back here and spew your keyboard he man BS opinion crappy i ola.
Last edited by Doc Olds; Jul 5, 2023 at 12:29 PM.
Reason: can't type
3/4 on the Gauge is, in fact, NORMAL. The gauge is like an idiot light with a needle, it is not providing you the actual temp of the coolant. One H3 might be at 3/4 on the dash gauge and actually have coolant temp at 200F, the next one can be half way and also have actual coolant temp at 200F. I would not get your panties all in a wad over what the gauge is showing unless you see the actual temp on a scanner.
H3s are SUPPOSED TO RUN in a set range! They are designed that way on purpose to be around 195-215F. Why??? Look it up. Emissions efficiency. Look up the TSPs on the topic, then after you have read those and have the information that GM provided its service techs to respond to this very situation, come back here and spew your keyboard he man BS opinion crappy i ola.
Idiot light with a needle aside. I think everyone in this thread can agree that gauge is not accurate. We're talking about H3 running hotter than 215F which has been suggested over and over to be normal, when it's not. GM introduced the new hotter t-stat for better emissions but at what cost to the vehicle? Sounds like a case of typical corporate bureaucracy, make someone in some department happy and move along.
I used a scanner to monitor mine and gotten to 227 at some points, which would be even hotter if I shut the engine off, not good. I literally went down the list and checked everything. I was puzzled by the location of the T-stat which is situated after the radiator at the engine inlet. Why would it be placed after the radiator? I took mine out and car doesn't run hotter than 215F, which seems to be within normal range now. So go figure, a lot of good information on this forum and I see you Doc repeating yourself a lot.
Idiot light with a needle aside. I think everyone in this thread can agree that gauge is not accurate. We're talking about H3 running hotter than 215F which has been suggested over and over to be normal, when it's not. GM introduced the new hotter t-stat for better emissions but at what cost to the vehicle? Sounds like a case of typical corporate bureaucracy, make someone in some department happy and move along.
I used a scanner to monitor mine and gotten to 227 at some points, which would be even hotter if I shut the engine off, not good. I literally went down the list and checked everything. I was puzzled by the location of the T-stat which is situated after the radiator at the engine inlet. Why would it be placed after the radiator? I took mine out and car doesn't run hotter than 215F, which seems to be within normal range now. So go figure, a lot of good information on this forum and I see you Doc repeating yourself a lot.
All in context.
You said outside temps over 100F. You seem to be aware that would result in higher then normal coolant temps, so add 10F to the normal coolant operating range and you would still be OK. The system was set up for expected ranges of outside temps, plus margins for extremes. Over 100F is extreme, it never gets that hot in most of the country. Your engine is not going to melt down over 10-15F heat load.
The TStat is at the Radiator Inlet side,(#954 in 305) which is outlet of coolant from the engine, so it is acting on the engine heated coolant. It stays closed at start up to build engine temp rapidly until warm enough to begin to open and allow flow out of the engine back to the radiator. Your upper radiator hose is the outlet from the radiator heading into water outlet (#308) into the engine to the water pump (#300) at the front to be pushed through the engine/system.
The gauge gets its feed from the ECT, but just points and does not display actual temp. It is located at the back of the block to measure engine heated coolant. #9 below.
A scan tool displays -38°F to +284°F. The Engine Coolant Temperature (ECT) sensor is mounted in the coolant stream. The powertrain control module (PCM) applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.
None of this measure the coolant exiting the radiator, which is always significantly cooler than what is inside the block. How much, 10-25F cooler always. Obviously, it has to "cool" the engine, or the system would not keep temps under control. I have a digital temp controller on my SFan4500 Efan that operates on the outlet side of the radiator on my 09 Alpha (not an I5 but near identical radiators and locations and more motor making heat) and it is always 15F + cooler than the actual ECT numbers.
Whether the TStat is at the top, or bottom, doesn't matter, the cooling system is till doing the same thing. None of this mentions the PCM's role in maintaining temp either. Get those panties out of the wad and relax for the big picture instead of staring at an idiot light with a needle.
You said outside temps over 100F. You seem to be aware that would result in higher then normal coolant temps, so add 10F to the normal coolant operating range and you would still be OK. The system was set up for expected ranges of outside temps, plus margins for extremes. Over 100F is extreme, it never gets that hot in most of the country. Your engine is not going to melt down over 10-15F heat load.
The TStat is at the Radiator Inlet side,(#954 in 305) which is outlet of coolant from the engine, so it is acting on the engine heated coolant. It stays closed at start up to build engine temp rapidly until warm enough to begin to open and allow flow out of the engine back to the radiator. Your upper radiator hose is the outlet from the radiator heading into water outlet (#308) into the engine to the water pump (#300) at the front to be pushed through the engine/system.
The gauge gets its feed from the ECT, but just points and does not display actual temp. It is located at the back of the block to measure engine heated coolant. #9 below.
A scan tool displays -38°F to +284°F. The Engine Coolant Temperature (ECT) sensor is mounted in the coolant stream. The powertrain control module (PCM) applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.
None of this measure the coolant exiting the radiator, which is always significantly cooler than what is inside the block. How much, 10-25F cooler always. Obviously, it has to "cool" the engine, or the system would not keep temps under control. I have a digital temp controller on my SFan4500 Efan that operates on the outlet side of the radiator on my 09 Alpha (not an I5 but near identical radiators and locations and more motor making heat) and it is always 15F + cooler than the actual ECT numbers.
Whether the TStat is at the top, or bottom, doesn't matter, the cooling system is till doing the same thing. None of this mentions the PCM's role in maintaining temp either. Get those panties out of the wad and relax for the big picture instead of staring at an idiot light with a needle.
With all due respect, I don't think you're correct about the coolant inlet/outlet location. Unless the diagram you're showing is incorrect. In your diagram, part #308 is actually the water outlet - see highlighted below. This means that the lower radiator hose and thermostat housing is the inlet to the engine. Thus the t-stat is acting on cooled radiator coolant rather than engine heated coolant as you're suggesting. Or is there more to it?
