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- #261
Brand new. I have also considered the water pump as well as a clogged jacket - that would suck, or a bad sending unit.
The Mule. (9 Viewers)
- Thread starter Hugh Heifer
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yooper
SILVER Star
Do you have an infrared thermometer? You could take some temp readings of the block and radiator when it looks like it's overheated. If they are way lower, then maybe the sending unit is bad, or the gauge.
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- #263
Thanks Yoop. I was just at Home Depot the other day and I saw one sitting there on sale and considered buying it just for that purpose.
I feel like I am on the right track! In order, easiest and cheapest i was thinking was:
1. Remove the thermostat and see how it acts
2. Get a thermometer and check the engine temp at the sending unit
3. Test/replace the sending unit and or gauge
4. Water pump seems fine but that is next
5. Last is a potentially clogged water jacket
Did I miss anything or does anyone have another suggestion. All the coolant lines are new, the radiator is new and the heater core was cleaned and is like new. I noticed that in the heat of the summer the temp would increase as I drove but decrease when I idled. Almost as though the thermostat got hot enough to open and allow circulation at idle but cooled enough while running that it would close and the temp would rise. Does that sound possible?
my truck does that exact same thing....... dont think I ever go far enough in the summer heat to see how high it will go. only on the highway. if I am on the trail... cool all day...... over 40 miles in hot/humid weather and on the highway and it will climb.
Poser looked at my truck and said they do that on hot humid days. no problems this fall
yooper
SILVER Star
No that doesn't make sense. Thermostat opens when the coolant temp gets above its set point, closes when it gets below, and the temperature of the system will not lag behind more than about thirty seconds. If the temp rises for any reason the thermostat will just open again.
The engine is simply making more heat when running at higher speed under load and your cooling system as a whole isn't keeping up with it.
Your fan isn't installed backwards, is it? It should be sucking air through the radiator, not blowing through it. If it was backwards you might see the same behavior...I just made that up though, I don't even know if it's possible to install it backwards.
yea... but how hot is it down there... I am talking like 90 degrees with a high humidity (very high) the more humid the air the less there actually is per cubic foot there for it takes more air to cool it down and it just cant keep up.
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- #267
What I was thinking was the the engine would get hotter at idle and the thermostat would open. While driving it would cool down enough and cause it to close sending the temp up. Now that the ambient temp her has fallen below 95 degrees everyday, the temp is not getting high enough to open the thermostat. That was my line of thinking anyway.
And ya know, Yoop, it is possible to put the fan on backwards. I recall reading something about someone doing that on here and it resulted in high temps. I will look but am pretty sure it is on right.
The engine kinda smells hot too. That worries me. It could just be the leaking oil burning off hot parts but it does seem hot.
Aaron - what temp thermostat are you running? I put the high temp range in mine and am wondering if that could be a source of my problem.
If i get an infrared thermometer, what temperature range should I be looking at and at what locations?
And ya know, Yoop, it is possible to put the fan on backwards. I recall reading something about someone doing that on here and it resulted in high temps. I will look but am pretty sure it is on right.
The engine kinda smells hot too. That worries me. It could just be the leaking oil burning off hot parts but it does seem hot.
Aaron - what temp thermostat are you running? I put the high temp range in mine and am wondering if that could be a source of my problem.
If i get an infrared thermometer, what temperature range should I be looking at and at what locations?
yooper
SILVER Star
Your understanding of how the thermostat works is correct but not your conclusions as to how that affects coolant/engine temperature are wrong. You are describing correct thermostat function: "While driving it would cool down enough and cause it to close sending the temp up.."....IF it got cool enough to cause the thermostat to close, then that is a sign that the system is dumping more heat than the engine makes while driving and at a greater differential than while idling, and IF the thermostat closes, then as the temp goes back up the thermostat will open again and the temperature will reach a steady state at a COOLER temperature than while idling. What you would see is a gradual lowering of the temperature while driving, then a gradual rise when idling, the exact oppposite of your symptoms. Correct thermostat function is not causing your problem.
If the thermostat is just plain stuck closed or doesn't fully open then perhaps that is the problem.
Engines overheat at idle sometimes because there is less air moving through the radiator but they actually make a lot more heat when running faster under load. The bonus of better air flow while driving usually is enough to solve the problem. Your system as a whole can't dump that extra heat despite more air flow. Either you don't have enough air flow or you don't have enough coolant flow.
You would expect the surfaces of the block and the radiator and the body of the water pump and the thermostat housing all to be slightly cooler than the coolant, but only slightly. If they are significantly cooler than your gauge says then the gauge or sender are bad.
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- Thread starter
- #269
In hopes of the simplest solution I just checked, the fan in on in the correct direction.
I am going to purchase a thermometer at HD tomorrow.
I will search for an operating temp this evening.
I am going to purchase a thermometer at HD tomorrow.
I will search for an operating temp this evening.
yooper
SILVER Star
what's the thermostat rating?
Ideal temp is generally around 190°F. I think hot on the gauge is about 230°F. So if the gauge says hot and your thermometer says 188°F then the gauge or sender are bad.
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- #271
I have the 190 installed. The other one is 180.what's the thermostat rating?
Ideal temp is generally around 190°F. I think hot on the gauge is about 230°F. So if the gauge says hot and your thermometer says 188°F then the gauge or sender are bad.
The other thing I just realized is there are three different sending units. '68 - 9/72, 9/72-10/79 and 10/79-8/92. The gauges are from late '72, the engine is a 2F and I have no idea what the sending unit came out of. I do not know if the the difference is in the thread pattern on the sending unit or if there is anything different about the ohms at which they function. If they were not properly matched that could be an issue but I would think they would all work under the same resistance.
yooper
SILVER Star
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- #273
Yeah. I was just flooding my head with tech and that obviously makes sense. Anything a little over 190 and it opens. Duh.
So you're desired operating range is basically 190-200 I think.
yooper
SILVER Star
Yeah. I was just flooding my head with tech and that obviously makes sense. Anything a little over 190 and it opens. Duh.
It would be pretty sweet if it was just the sender.
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- #275
It would be pretty sweet if it was just the sender.
Undeniable. I will also take a look at the lower hose while at temp. Maybe it is collapsing.
hugh-
now sure what thermo I am using.... I got it from cdan.... and just told him I wanted the one that came in my truck
I would guess the 180 one
now sure what thermo I am using.... I got it from cdan.... and just told him I wanted the one that came in my truck
I would guess the 180 one
- Thread starter
- #277
Got an infrared thermometer today. We will see what we come up with temp wise.
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- #278
GOOD NEWS!!!
Thanks to Yooper's suggestion, I purchased a Ryobi infrared thermometer and the beast is running at 179F all day long.
That means it is either the gauge or the sender (or I guess wiring).
I am so happy it is not something more serious. Now to try to sort out the issue. I really want that s*** working right before hitting the trail so if it actually starts to get hot I will know for sure. There are all kinds of places on the net about testing both the gauge and the sender so I will start with that.
Thanks to Yooper's suggestion, I purchased a Ryobi infrared thermometer and the beast is running at 179F all day long.
That means it is either the gauge or the sender (or I guess wiring).
I am so happy it is not something more serious. Now to try to sort out the issue. I really want that s*** working right before hitting the trail so if it actually starts to get hot I will know for sure. There are all kinds of places on the net about testing both the gauge and the sender so I will start with that.
yooper
SILVER Star
AWESOME!
yooper knows. write that down on your forehead.
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