As some of you here know I have had a over cooling condition in my truck for quite a while. It seems to be getting worse. No matter what tstat i am using now the temp is hard pressed to get over 175 and will drop to 155 but seems to stay just below 170 most of the time. This is in 70 weather, in town or high way and with 2 of my winter fronts in place. I am on my 7th tstat with the same results. I even sent one of them to Mike and it runs fine for him. After 6 190* tstats and one cummins 180* tstat with almost the same results with them all I am at my wits end. I have also replaced the temp sender twice and no differance. I am wondering has anyone else here had this problem. Not long ago I replaced the heater core and refilled the engine thru the tstat hole and even put water in thru the heater supply and return. I cant beleieve there is any air in the block. The gauge will move between 155 and 175 but I cant get it any higher unles I am pulling the rv. But even then about 180 is the best I can seem to get.. I have noticed of late it the temp drops below 165 i get some EGT fluctuations and a little boost gauge fluctuations. If any body has had this problem I am very interested in hearing about them and any solutions you might have found.

Is it possible that the temp gauge is incorrect?

The only things I can think of is that you are getting excessive flow through the heater core or there is a leak in the thermostat housing somehow. Or your housing is out of spec.

I found out a way to test the sensor. Pull the sensor out of the block and hook it back up and place the sensor back into a cup of heated water. Now measure the heated water with meat thermometer and see what the ECM reports with a ScanGauge II if the numbers match then is fine... If not then the sensor is failing... Something I learned with Pepsi71ocean...

What about the gauge on the dash? Can you use something like a potentiometer to alter voltage to see what the values do on the gauge?See x amount of volts with the potentiometer correlates to so and so degree on the gauge. Or is it a resistive reading?

is your fan clutch locked up to where its spinning the fan full bore?

When mine was acting goofy I spent $35 on a mechanical Isspro temp gauge and mount. It stays right around 192-193 when the dash says 188. I put it 2 ports back from the oe sensor. Do you happen to have a high idle box?

When mine was acting goofy I spent $35 on a mechanical Isspro temp gauge and mount. It stays right around 192-193 when the dash says 188. I put it 2 ports back from the oe sensor. Do you happen to have a high idle box?

I think I suggested installing an aftermarket temp gauge, just for S&Gs.. If you need one, I believe I have a spare AutoMeter temp gauge and sender that I can shoot your way..

What about the gauge on the dash? Can you use something like a potentiometer to alter voltage to see what the values do on the gauge? See x amount of volts with the potentiometer correlates to so and so degree on the gauge. Or is it a resistive reading?

See IAT Temps... ECT sensor ohm values are the same. [TABLE] [TR] [TD=width: 50%, bgcolor: #3870cc, align: center]Temperature[/TD] [TD=width: 50%, bgcolor: #3870cc, align: center] Resistance[/TD] [/TR] [TR] [TD=width: 50%, align: center] 13°F[/TD] [TD=width: 50%, align: center] 56K ohms[/TD] [/TR] [TR] [TD=align: center] 26°F[/TD] [TD=align: center] 39K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 87ºF[/TD] [TD=width: 50%, align: center] 7.4K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 91°F[/TD] [TD=width: 50%, align: center] 6.8K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 100°F[/TD] [TD=width: 50%, align: center] 5.6k ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 107°F[/TD] [TD=width: 50%, align: center] 4.7K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 112°F[/TD] [TD=width: 50%, align: center] 4.3K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 119ºF[/TD] [TD=width: 50%, align: center] 3.6K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 123ºF[/TD] [TD=width: 50%, align: center] 3.3K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 127ºF[/TD] [TD=width: 50%, align: center] 3.0K ohms[/TD] [/TR] [TR] [TD=width: 50%, align: center] 132ºF[/TD] [TD=width: 50%, align: center] 2.7k ohms[/TD] [/TR] [TR] [TD=align: center] 143°F[/TD] [TD=align: center] 2.2k ohms[/TD] [/TR] [TR] [TD=align: center] 148°F[/TD] [TD=align: center] 2.0k ohms[/TD] [/TR] [TR] [TD=align: center] 163°F[/TD] [TD=align: center] 1.5k ohms[/TD] [/TR] [TR] [TD=align: center] 173°F[/TD] [TD=align: center] 1.2k ohms[/TD] [/TR] [TR] [TD=align: center] 184°F[/TD] [TD=align: center] 1.0k ohms[/TD] [/TR] [/TABLE]

Is it possible that the temp gauge is incorrect?

I don't think so. I have a spare speedo and installed it when my ecm went out and it acted no different.

- - - Updated - - -

Is it possible that the temp gauge is incorrect?

I don't think so. I have a spare speedo and installed it when my ecm went out and it acted no different.

- - - Updated - - -

By they way I see the avatar has grown up a little.

The only things I can think of is that you are getting excessive flow through the heater core or there is a leak in the thermostat housing somehow. Or your housing is out of spec.

Correct me if I am wrong, but I believe the flow thru the heater core is constant. When I replace my core I saw nothing to restrict the flow. It appeared to me the flow is constant and the temp in the vehicle is controlled other means. I know some older vehicles I have owned had a vlave that controlled the amount of flow from the engine. could be wrong on that though. As far as leaks, I am loosing no coolant and the tstat housing is the stock one.

- - - Updated - - -

I found out a way to test the sensor. Pull the sensor out of the block and hook it back up and place the sensor back into a cup of heated water. Now measure the heated water with meat thermometer and see what the ECM reports with a ScanGauge II if the numbers match then is fine... If not then the sensor is failing... Something I learned with Pepsi71ocean...

This seems interesting. I will have to try this tomorrow. I have no scan gauge, but if I immerse the sensor in 190* water the temp gauge should be near the same.

- - - Updated - - -

What about the gauge on the dash? Can you use something like a potentiometer to alter voltage to see what the values do on the gauge?

See x amount of volts with the potentiometer correlates to so and so degree on the gauge. Or is it a resistive reading?

While I don't think it is the gauge on the dash, I have thought that it might be the signal thru the wiring. I have 3 senders and they all do the same thing. I also have a spare speedo which registers the same as my original.

- - - Updated - - -

is your fan clutch locked up to where its spinning the fan full bore?

Negative. When my fan comes on it sounds like a Turbo prop engine is running with me.

- - - Updated - - -

When mine was acting goofy I spent $35 on a mechanical Isspro temp gauge and mount. It stays right around 192-193 when the dash says 188. I put it 2 ports back from the oe sensor. Do you happen to have a high idle box?

I remember that thread and thought about getting one myself, but did not. My temps a varying so much more than yours it is ridiculous. Still might try one though. No high idle box on mine.

- - - Updated - - -

I think I suggested installing an aftermarket temp gauge, just for S&Gs..

If you need one, I believe I have a spare AutoMeter temp gauge and sender that I can shoot your way..

I have thought of doing that, but think it is more a signal problem thru the wiring. I am on my 3rd sender with the same results. I have even changed the cluster out with the same results. I have good heat. and all seems normal tempwise under the hood. That is more from feel than any scientitfic results though. I very much appreciate the offer on the gauge, but I am going to play with it all some more for now.

- - - Updated - - -

See IAT Temps... ECT sensor ohm values are the same.

[TABLE]

[TR]

[TD=align: center]Temperature

[/TD]

[TD=align: center] Resistance

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 13°F

[/TD]

[TD=width: 50%, align: center] 56K ohms

[/TD]

[/TR]

[TR]

[TD=align: center] 26°F

[/TD]

[TD=align: center] 39K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 87ºF

[/TD]

[TD=width: 50%, align: center] 7.4K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 91°F

[/TD]

[TD=width: 50%, align: center] 6.8K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 100°F

[/TD]

[TD=width: 50%, align: center] 5.6k ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 107°F

[/TD]

[TD=width: 50%, align: center] 4.7K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 112°F

[/TD]

[TD=width: 50%, align: center] 4.3K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 119ºF

[/TD]

[TD=width: 50%, align: center] 3.6K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 123ºF

[/TD]

[TD=width: 50%, align: center] 3.3K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 127ºF

[/TD]

[TD=width: 50%, align: center] 3.0K ohms

[/TD]

[/TR]

[TR]

[TD=width: 50%, align: center] 132ºF

[/TD]

[TD=width: 50%, align: center] 2.7k ohms

[/TD]

[/TR]

[TR]

[TD=align: center] 143°F

[/TD]

[TD=align: center] 2.2k ohms

[/TD]

[/TR]

[TR]

[TD=align: center] 148°F

[/TD]

[TD=align: center] 2.0k ohms

[/TD]

[/TR]

[TR]

[TD=align: center] 163°F

[/TD]

[TD=align: center] 1.5k ohms

[/TD]

[/TR]

[TR]

[TD=align: center] 173°F

[/TD]

[TD=align: center] 1.2k ohms

[/TD]

[/TR]

[TR]

[TD=align: center] 184°F

[/TD]

[TD=align: center] 1.0k ohms

[/TD]

[/TR]

[/TABLE]

Thanks for the info here. I will use when is get some time.

Here is what I tried before I left for Indiana on Sunday. I boiled some water in a tea pot and poured it in a coffee cup. I immersed the sensor in the water and put a meat thermometer it with it. The thermometer said near170* and the dash gauge was reading near the same. I also tried using my infrared(cheap Ryobi model) but could not seem to get a good treading on the water. It worked good on solid objects but not the water. The gauge seemed to follow the water temp as it cooled down. I did not have time to check the electronics before leaving. When I left it was 60* out, 2 of my winter fronts in, and sunny. I was lucky to see 160* at 80 mph. The whole time I was seeing fluctuations in the egt(pretty wild swings) and some fluctuation in boost pressure. you could also feel it in the performance of the truck like the engine was defueling. Max boost I was seeing was just 20# to 22#. I would normally see 32# to 34#. This is at WOT. When I came to the grade on I40 up to Ashville NC(6% about 6 to 7 miles long) the temp actually went up to 180* or 185* by the time I reached the top, but cooled back off in just 3 or 4 miles. Once the temp went over 160 to165 I had full boost and all was well. It stayed this way(low temps and reduced performance) for the next 200 miles. About half way thru Kentucky as it got colder, darker, and started to rain the engine started to warm up a little to 170*. All the fluctuations stopped and performance was normal. It stayed that way the rest of the trip and is still trying to get to 170* since I have been here. In the meantime I am just going to put a mechanical gauge and see what it says.

Here is what I tried before I left for Indiana on Sunday. I boiled some water in a tea pot and poured it in a coffee cup. I immersed the sensor in the water and put a meat thermometer it with it. The thermometer said near170* and the dash gauge was reading near the same. I also tried using my infrared(cheap Ryobi model) but could not seem to get a good treading on the water. It worked good on solid objects but not the water. The gauge seemed to follow the water temp as it cooled down. I did not have time to check the electronics before leaving. When I left it was 60* out, 2 of my winter fronts in, and sunny. I was lucky to see 160* at 80 mph. The whole time I was seeing fluctuations in the egt(pretty wild swings) and some fluctuation in boost pressure. you could also feel it in the performance of the truck like the engine was defueling. Max boost I was seeing was just 20# to 22#. I would normally see 32# to 34#. This is at WOT. When I came to the grade on I40 up to Ashville NC(6% about 6 to 7 miles long) the temp actually went up to 180* or 185* by the time I reached the top, but cooled back off in just 3 or 4 miles. Once the temp went over 160 to165 I had full boost and all was well. It stayed this way(low temps and reduced performance) for the next 200 miles. About half way thru Kentucky as it got colder, darker, and started to rain the engine started to warm up a little to 170*. All the fluctuations stopped and performance was normal. It stayed that way the rest of the trip and is still trying to get to 170* since I have been here. In the meantime I am just going to put a mechanical gauge and see what it says.

The mechanical gauge will give a good reading I am sure, but as a quick check since you have the infared thermometer, throw it on the block right by the thermostat. Might be interesting if it reads higher than the gauge. (nerd on) Infared thermometers are highly variable from material to material due to the amount of heat they give off. Black matte items give the most accurate readings as they have the highest emissivity. (nerd off(

Pepsi71ocean is running a 200*F thermostat and doing some bench testing on it. So far he's liking the good solid 197-204*F temps from it and good strong heat from the heater.

The mechanical gauge will give a good reading I am sure, but as a quick check since you have the infared thermometer, throw it on the block right by the thermostat. Might be interesting if it reads higher than the gauge. (nerd on) Infared thermometers are highly variable from material to material due to the amount of heat they give off. Black matte items give the most accurate readings as they have the highest emissivity. (nerd off(

I have done that, but get different readings on the tstat housing and the block near the tstat housing. Not sure what to believe when I do it. Maybe I need to learn how to turn my nerd on. You must know Mr. Miagi. Nerd on, Nerd off.

a little update. I just took off on a trip to Terre Haute In with the rv. Temps were a little higher especially on hills, but not much. Came to the grade up to Ashville nc and the temps started to climb. The last time I looked at the gauge it was reading near 200*. That has not been unusual towing on that grade. I few seconds later I heard a pop and saw the steam venting from under the hood. I got off the road and shut her down. Started looking for a blown hose and then realized I had blown the end of the radiator off. Never lost any power just the radiator. I have always been thinking this was a cooling problem and not electronic. But I might be wrong unless the radiator was just gone. The hoses are the ones that came on the truck and I would have thought one of those would have let go first. Any way I have a new radiator on the way and we will see what happens. I have a 217 engine overheat code also.

lol.........first time I have read this thread and I was going to post something that is the most common for overcooling and the problem just appeared to you as I read you just posted a few minutes ago.

One of the most common reasons for overcooling are partially plugged radiator cores. It causes the coolant to spend more time in the radiator than it normally would which pulls more of the heat out of the coolant than normal.

Nobody mentioned the first thing to be done on any engine with erratic cooling issues is to shoot the top and bottom hoses to see what the temp drop is. As a very general range If you start seeing more than 30+- degrees drop this is an indicator of plugged cores.

With newer vehicles aluminum radiators it is more important than ever to mix coolant with distilled or RO water to keep any and all mineral and other solids from scaling the inside of the aluminum cores.

It is also almost as important to take coolant samples the same as we do oil sampling, believe it or not at work we get just as many bad coolant samples back as we do oil samples. Every oil lab has coolant sampling capabilities too. Most samples for new equipment always come back bad either the glycol level is too strong or too weak or the solid particulate matter is too high, on older equipment the additives deplete just like oils and believe it or not on engines liquid cooled turbos the coolant can become burnt.

and believe it or not on engines liquid cooled turbos the coolant can become burnt.

Is that because you boil the "hell" out of it? :lol:

lol.........first time I have read this thread and I was going to post something that is the most common for overcooling and the problem just appeared to you as I read you just posted a few minutes ago.

One of the most common reasons for overcooling are partially plugged radiator cores. It causes the coolant to spend more time in the radiator than it normally would which pulls more of the heat out of the coolant than normal.

Nobody mentioned the first thing to be done on any engine with erratic cooling issues is to shoot the top and bottom hoses to see what the temp drop is. As a very general range If you start seeing more than 30+- degrees drop this is an indicator of plugged cores.

With newer vehicles aluminum radiators it is more important than ever to mix coolant with distilled or RO water to keep any and all mineral and other solids from scaling the inside of the aluminum cores.

It is also almost as important to take coolant samples the same as we do oil sampling, believe it or not at work we get just as many bad coolant samples back as we do oil samples. Every oil lab has coolant sampling capabilities too. Most samples for new equipment always come back bad either the glycol level is too strong or too weak or the solid particulate matter is too high, on older equipment the additives deplete just like oils and believe it or not on engines liquid cooled turbos the coolant can become burnt.

[ATTACH=CONFIG]5245[/ATTACH][ATTACH=CONFIG]5246[/ATTACH][ATTACH=CONFIG]5247[/ATTACH]Here are photos of the old radiator. since my truck sees highway and job sites 99% of the time I thought I would be somewhat immune to the clogging from the puke bottle. It appears I was wrong. It seems to me with this clogging I should not be over cooling, but over heating. Other than hitting 200*+ going up the mountain on Sunday, 175* is about the best I can get. for most of the trip I stayed 160* to 165*. Yesterday after warming the truck and running up the interstate back the campground I was at 160* when I parked. I shot the tstat housing and it read near 160, around the base of the housing only 145. at the exit of the housing 145 also and at the radiator hose into the radiator only 120. I could grab the hose and hold it in my bare hand and it only felt warm. When I squeezed the hose if felt soft like there was no pressure on it. I loosened the cap and it sprayed coolant all over my hand and was only warm to touch. So I am believing my gauge is giving me an reasonably accurate reading.I just don't understand why the tstat is not staying closed in order to get the engine to temp. even if 30* coolant is entering the engine why is the tstat allowing the coolant to pass before it gets to temp? As far as internal clogging goes the end of the radiator that blew off shows none. all of the passages are wide open. Any way after the new radiator, a new tstat, and new coolant my temps are running about 5 to 10* cooler and about 155 to 160 with occasional +'s and -"s. The only thing I have not replaced is the fan clutch. I still hear it when it engages at start up and when it does while under a heavy load. It came on and off several times on the way here. I watched when I shut down the engine and it spun maybe 2 revolutions after the engine stopped and I could move it with hand. According to the Haynes manual it should spin with resistance when hot. Mine will not spin as freely as Mike's does, and I would not want to try and stop it while the engine is running. I guess I will replace the clutch and see what happens. It is the only part of the system I have not replaced.

I know I am electronically slow but I just ohm'ed the sender as I was instructed to do(since MM pointed out the right way to do it). I have 1.2 ohms with the gauge reading just under 165*. Put in a mechanical gauge and it reads 200*, but during install my head mechanic seemed to let the capillary tube touch the + terminal on the battery and now it wont read below 140* no matter what. So I will have to get another gauge. I would fire the mechanic, but I am the only one I have.

LOL fire him anyway

[ATTACH=CONFIG]5245[/ATTACH][ATTACH=CONFIG]5246[/ATTACH][ATTACH=CONFIG]5247[/ATTACH]Here are photos of the old radiator. since my truck sees highway and job sites 99% of the time I thought I would be somewhat immune to the clogging from the puke bottle. It appears I was wrong. It seems to me with this clogging I should not be over cooling, but over heating. Other than hitting 200*+ going up the mountain on Sunday, 175* is about the best I can get. for most of the trip I stayed 160* to 165*. Yesterday after warming the truck and running up the interstate back the campground I was at 160* when I parked. I shot the tstat housing and it read near 160, around the base of the housing only 145. at the exit of the housing 145 also and at the radiator hose into the radiator only 120. I could grab the hose and hold it in my bare hand and it only felt warm. When I squeezed the hose if felt soft like there was no pressure on it. I loosened the cap and it sprayed coolant all over my hand and was only warm to touch. So I am believing my gauge is giving me an reasonably accurate reading.I just don't understand why the tstat is not staying closed in order to get the engine to temp. even if 30* coolant is entering the engine why is the tstat allowing the coolant to pass before it gets to temp? As far as internal clogging goes the end of the radiator that blew off shows none. all of the passages are wide open. Any way after the new radiator, a new tstat, and new coolant my temps are running about 5 to 10* cooler and about 155 to 160 with occasional +'s and -"s. The only thing I have not replaced is the fan clutch. I still hear it when it engages at start up and when it does while under a heavy load. It came on and off several times on the way here. I watched when I shut down the engine and it spun maybe 2 revolutions after the engine stopped and I could move it with hand. According to the Haynes manual it should spin with resistance when hot. Mine will not spin as freely as Mike's does, and I would not want to try and stop it while the engine is running. I guess I will replace the clutch and see what happens. It is the only part of the system I have not replaced.

Drip, Don`t want to derail your thread... but WTH could blow your radiator up like that???