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Unread 07-07-2013, 10:12 PM   #16
Newtons3
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For most of us, operating temps are such that thermostats, under normal conditions, are all the way open.

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Unread 07-07-2013, 10:13 PM   #17
Newtons3
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Quote:
Originally Posted by Paradise XJ View Post
The coolant in the "COLD" side of the radiator is hot...about 192 . The coolant never gets even near ambient temperature, once the t-stat opens it's open, it doesn't cycle on/off, so ALL the coolant circulating at ~192-and up. It cools some as it passes through the radiator but not down to ambient temperature. It's just a 1 1/4" tube that the tranny fluid travels through, surrounded by HOT coolant, nothing more complicated, no fins, ribs, no network of capillary tubes. So the transmission fluid in the radiator tube is heated.

The tranny fluid WILL get too cold if you're driving in sub-Z temps and don't have the radiator in the loop. Thicker cooler fluid is not necessarily better.
If you live in Florida, or somewhere that's always warm, the tranny doesn't need any help generating heat. E.G
All true.
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Unread 07-07-2013, 11:05 PM   #18
djb383
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Originally Posted by Newtons3 View Post
For most of us, operating temps are such that thermostats, under normal conditions, are all the way open.
Really.......even in cold, cool, moderate temps like when using the heater or no a/c needed?
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Unread 07-08-2013, 03:55 AM   #19
Timo_90xj
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Quote:
Originally Posted by djb383 View Post
Really.......even in cold, cool, moderate temps like when using the heater or no a/c needed?
In cold weather, t-stat closes and opens as necessary. However, once the engine has warmed up it pretty much never fully closes apart from the very harshest cold.

I've had the e-fan kick on multiple times on my niner (they don't use viscous fan at all) when it's around -15*F outside, so it goes on to show how much heat engines actually produce -> that being said it also goes on to show how much heat there is in the radiator, which in turn means in many cases you do need an auxiliary tranny cooler even if you don't tow often. As it's been said, in warm climate where below- freezing temps aren't common I really see no reason to route the tranny fluid through the radiator; just use an external cooler in front of the radiator/ AC condenser.
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Unread 07-08-2013, 08:04 AM   #20
Newtons3
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Quote:
Originally Posted by djb383 View Post
Really.......even in cold, cool, moderate temps like when using the heater or no a/c needed?
Tracking coolant temps on my Scangauge II, my operating temps fluctuate between 205-220. The thermostat is fully open around 195 or so, mine is pretty close. When I was swapping thermostats, the operating temps didn't drop with 180 or 165 thermostats. I could raise them a bit with a 205. The thermostat is primarily for warming up. Actual operational temps are harder to change.

More directly to the question, yes, here, in our winter, my Jeep takes longer to warm up (maybe a mile or two more), but the temps stay the same. What does change, but less than you'd think, is the temperature drop across the radiator.

I have had my jeep in weather cold enough to cause visible fluctuations on my dash gauge, but I wasn't tracking op. temps through the ECU then. Also, we NEVER see that weather here.
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Unread 07-08-2013, 10:18 PM   #21
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U must be running a 180 stat if it's fully open at 195. A t-stat does one thing and one thing only.......control minimum coolant temp. The other cooling system components along with their condition, ambient temps and driving conditions determine maximum coolant temp.

We use a ScanGauge in our XJ as well and in cool/cold weather it will run right at the stat rating, even a few degrees below the stat rating when ambient temp is cool enough to run the heater. Moving the ScanGauge from the XJ to another vehicle shows the same thing in cool weather. The day we drove our XJ home from the auction ambient was 17F.......ScanGauge fluctuated between 192 and 197, iirc. Will it run 197 in triple digit ambient.....I doubt any stock XJ will.
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Unread 07-09-2013, 09:18 AM   #22
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Right now, I am running a fast acting high flow thermostat left over from my last race car. It does react right at the rated temperature, which, as you alluded to, may mean if compared to others it is actually coming in earlier. Your op. temps in the ambient in Texas are interesting. As I said, mine runs no less than 205. Right now my Wrangler is running 210-215ish. My Cherokee has been off the road for a while so I can't verify today. I am flushing/refilling the Wrangler today and will be moving the Scangauge over to it. I'll be tracking actual op temps along with IAT.
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Unread 07-09-2013, 01:21 PM   #23
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The temperatures across the radiator everyone is quoting just don't seem right. I grabbed my temp gun before I drove my 1998 Windstar to work yesterday. About 30 miles at 70 on flat land. I know from checking with my laptop that the computer reports it running at 200 on the nose.

As soon as I hit the parking lot at work I checked the rad tanks and the trans lines. The engine was at 200 I assume, the top hose and hot tank came in at 162, bottom hose and cold tank 100, hot trans line 140 cold line 110.

The out side temp was 70.

NOW KEEP IN MIND THAT the radiator in the van is much bigger than the XJ's and it only has a 3.0 v6. What I found interesting is how close to ambient the cold sides got. I will set the computer up in the jeep and drive it tomorrow.

Stay tuned...
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Unread 07-09-2013, 04:30 PM   #24
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I worked half the day on my Wrangler's cooling system today. I can assure you, the lower tank was nowhere near 100 degrees. I know the top tank was 210, sometimes a hair more. Now I wish I had gotten my Raytech out. I need it anyway to measure floorboard temps for my other project. Scangauge tomorrow and Raytech and I'll track what mine is doing. The Windstar's we used to have in our company fleet ran so hot we could barely keep them from boiling over. Massive cooling issues. And... the longest serpentine belt I have ever seen on an automobile. Holy crap that thing was long.
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Unread 07-10-2013, 11:29 AM   #25
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So... Just got the Scangauge installed and took it for a ride. I also shot the radiator with my IR gun. Scangauge says 200 degrees op temp with A/C on idling in the driveway. When I turn the A/C off and my fan catches up (>5 minutes) it reads 195. Running down the road, I am showing 204. This is all with an ambient air temperature of 88 (hadn't warmed up yet). When I shot the tanks of my radiator, I got some interesting readings similar to what I've seen before. The top tank read 150-ish depending on where I shot it and the bottom tank read 113-119 again, depending. I cannot consider these to be the true coolant temps though for obvious reasons. The fluid coming out of my engine, past my thermostat is 195-204 degrees while all of this is happening. There is no way possible that it loses 50+ degrees in the upper radiator hose. Unfortunately, there are no ports for sending units in my tanks. My last radiator had them. I will track temps this week and see what gives.
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Unread 07-10-2013, 11:57 AM   #26
dave564
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Well I found that my numbers were way off with my Windstar. I plugged in the laptop and found that the temp sensor is reporting 162 degrees, even though I have a 195 T stat. I guess I know what I will be this weekend.
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Unread 07-10-2013, 12:10 PM   #27
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Quote:
Originally Posted by Newtons3 View Post
So... Just got the Scangauge installed and took it for a ride. I also shot the radiator with my IR gun. Scangauge says 200 degrees op temp with A/C on idling in the driveway. When I turn the A/C off and my fan catches up (>5 minutes) it reads 195. Running down the road, I am showing 204. This is all with an ambient air temperature of 88 (hadn't warmed up yet). When I shot the tanks of my radiator, I got some interesting readings similar to what I've seen before. The top tank read 150-ish depending on where I shot it and the bottom tank read 113-119 again, depending. I cannot consider these to be the true coolant temps though for obvious reasons. The fluid coming out of my engine, past my thermostat is 195-204 degrees while all of this is happening. There is no way possible that it loses 50+ degrees in the upper radiator hose. Unfortunately, there are no ports for sending units in my tanks. My last radiator had them. I will track temps this week and see what gives.
Those tank temps might be right. When did you check them, fresh after driving, or just letting it warm up in the driveway? With the engine just idling the heater core can almost handle all the cooling. Only the excess heat above the Thermostat rating will be channeled to the radiator.

EXAMPLE: I now know the Windstar T stat is opening at about 160. When I checked it last night after warming up a bit it at work, the hot HEATER HOSE was at 158 and just past the T stat housing the top hose was 110. After about a 15 minute idle the heater hose was at 162 and the top hose was only 144. I stopped after about 15 miles on the road and both hot hoses were 162 with the cold tank at 124.
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Unread 07-10-2013, 12:33 PM   #28
Newtons3
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I disagree. I know with quite a bit of certainty that the fluid coming into the upper hose was 195-204. Therefore, the fluid moving into the upper tank should be right there or at best, a couple of degrees cooler, not 50. I have sender halfway down my upper hose that can tell me when the water temp is over 195; it definitely was. Also, observing the coolant yesterday confirmed that I have excellent flow through the radiator (pretty good velocity too). There is no way possible that the heater core can radiate that much heat, especially without air channeled across it.
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Unread 07-10-2013, 12:52 PM   #29
djb383
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Quote:
Originally Posted by Newtons3 View Post
Right now, I am running a fast acting high flow thermostat left over from my last race car. It does react right at the rated temperature, which, as you alluded to, may mean if compared to others it is actually coming in earlier. Your op. temps in the ambient in Texas are interesting. As I said, mine runs no less than 205. Right now my Wrangler is running 210-215ish. My Cherokee has been off the road for a while so I can't verify today. I am flushing/refilling the Wrangler today and will be moving the Scangauge over to it. I'll be tracking actual op temps along with IAT.
R u saying in cool/cold weather using a 195 stat u see 205-215? I'm not sure what a fast acting stat is. I always test prior to installation and they all open very slowly, very smoothly, even if dropped into boiling water. Most stats r designed to be closed or ever so slightly open at their rated temp. A 195 stat, for example, will appear closed at 195 and ever so slowly open a coolant exceeds 195. If a 195 stat is wide open at 195 it's either broken, or it's a 180 stat.
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Unread 07-10-2013, 03:15 PM   #30
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Yes. In cold weather, once up to operating temp, my engine coolant temp is 205-ish. I'll have to wait until this winter to know if the changes I've made make any difference, but I would bet they don't. They weren't supposed to. These changes were only to increase the efficiency of my radiator/condenser, reduce underhood temperatures, and reduce firewall, floorboard temps. And, again, this is NOT a standard thermostat. I tested six or seven a couple of years back to collect information about just such a topic. This is the one I ended up sticking with. It is a fast acting. It does open between 192 and 195. It is truly open at 195. That's where I want it.
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