Coolant Temperature guage

[Excalibur07]

Hi guys. I have a 1999 Ford Explorer with the V8 engine including tow package. There are 172,000 miles on it now. It has been a great truck, very reliable, no major things to fix at all. Once a year I tow my boat (boat and trailer weigh 6,500 lbs. - I checked on a truck scale) up a major mountain highway here in British Columbia - the highway is called the Coquihalla and it is infamous around here for killing cars, buses and trucks of all descriptions (try a Google search on "Highway Thru Hell" television program). I have towed my boat up there 9 times without any hint of a problem so I am really impressed with the Explorer's ability to tow. Sorry for the long preamble - I am getting to my question. At the toughest part of the road there is a hill over 30 km (18 miles) long. The very steepest part of that hill is right at the end, where I have to put the truck in 1st. gear to have enough power to keep going. I am in the slow lane with flashers on, going about 45 km/hr (27 miles per hour), revving at around 3,000 rpm or so. Even with that long hill and the worst part of the climb for about 3 miles at the very end of it, in heat up to 30 degrees Celsius (85 Fahrenheit), the temperature guage does not move at all past it's normal operating range. So whether I am driving around town on level ground at 70 degree F or towing a 6,500 lb. with 4 people in the car, camping gear, up an 18 mile long hill at close to 90 degrees F in first gear, the guage reads the same - right in the middle of the normal range. As I said I have never had a problem or even the hint of a problem but I am wondering if the temperature guage is working properly. It certainly does work in that it registers cold when starting and warms up normally and sets in the normal range - but should'nt it go up a fair amount to reflect the extreme conditions when towing up that hill? I wonder if anybody else has had a similar experience? I am already impressed with the Explorer's towing ability up that hill but I am a little nervous at the same time thinking that perhaps I am not getting the real picture about the actual coolant (and therefore transmission) temps. I read on another forum for another brand of car that some temperature guages do not function well past the normal range - not sure why this would be so just askiin'...

 

[JimMadsen]

You could always pick up a cheap odb cable and download some free software. Do a data log on a laptop while making the trip and see exactly what is going on.

 

[koda2000]

that's because the TEMP indicator is not really a gauge. there are no numbers on it. if your coolant is w/in the normal operating range, the needle pretty much stays in the center. if you want to know what the actual coolant temp is you can follow JimMadsen's advice and see what your PCM is actually seeing, or use a scangauge. BTW your oil pressure indicator isn't a real gauge either. the oil pressure switch tells the "gauge" you have oil pressure or you don't. if you do, the needle sits in the center.

 

[Excalibur07]

Thanks for the replies. I understand that the needle does not give me an actual temperature but it does move, that is, when it's warming up it barely registers, then moves up a little then more, etc.. until it reaches the normal operating range. I would think that it should go up if the engine temperature goes higher? I recently bought and OBD reader which I can use to get the actual coolant temperature and I will do that this July when I tow the boat up there again - but in the meantime, it does seem as if the guage should climb up if the coolant is getting hotter than the regular operating range. Maybe the cooling system is that good that the thermostat can just keep it in the optimal operating range no matter what the condition of the tow?

 

[koda2000]

Thanks for the replies. I understand that the needle does not give me an actual temperature but it does move, that is, when it's warming up it barely registers, then moves up a little then more, etc.. until it reaches the normal operating range. I would think that it should go up if the engine temperature goes higher? I recently bought and OBD reader which I can use to get the actual coolant temperature and I will do that this July when I tow the boat up there again - but in the meantime, it does seem as if the guage should climb up if the coolant is getting hotter than the regular operating range. Maybe the cooling system is that good that the thermostat can just keep it in the optimal operating range no matter what the condition of the tow?

if you really overheat the engine the needle will go higher, but all three of my trucks stay pretty much in the center once warmed up. i had a bad thermostat on one truck last winter and the needle barely moved off "C" yet i still got pretty decent heat out of the heater. i don't know what the NORMAL range is, but it must be something like 180-220F.

 

[radman]

Infrared Heat Gun

Hi Ex,
If you really want a quick and cheap idea of what is going on with your engine pick up one of these <http://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-60725.html> and as you top the grade at the end of the 18 mile climb pull over and pop the hood and see what you have at the thermostat housing, that will be your warmest coolant.
Mike

 

[masospaghetti]

I've found that the needle will sit right in the middle of the range even if the temperature fluctuates some. I'm sure this was done on purpose to keep people from worrying when the temperature goes up and down. My Fiero has a needle without this feature and its obvious when the thermostat first opens (needle drops a few ticks), when the engine heats up in traffic, and when the cooling fan turns on. Someone who is unfamiliar with cars would probably worry that something was wrong, the fact that the needle was moving around.

Now just because the coolant is within normal range doesn't mean the transmission isn't overheating. You may consider a transmission temperature gauge when doing heavy towing. Luckily the V8 Explorer has a robust transmission and an auxiliary transmission cooler.

 

[pbnj22]

i keep a scan gauge on mine and it never exceeds 190.. it will stay between 176 and 188 99 percent of the time. Then again i haven't checked in the summer. also... i thought towing overheated the trans not the motor? which our trucks do not have a trans temp gauge and the computer does not even know what it is which sucks..

 

[AP9]

Based on ScanGaugeII readings on my OHV V6, that spot right in the middle (needle through the temperature gauge symbol) is where it stays from about 177 to 210. (Never gone above 210 since I've been monitoring it with ScanGauge).
[MENTION=180726]pbnj22[/MENTION]: the 5R55E transmission fluid temperature is available over OBD-II. Requires X-Gauge to be programmed though. Does the 4R70W not have a sensor I wonder?

 

[pbnj22]

Based on ScanGaugeII readings on my OHV V6, that spot right in the middle (needle through the temperature gauge symbol) is where it stays from about 177 to 210. (Never gone above 210 since I've been monitoring it with ScanGauge).
[MENTION=180726]pbnj22[/MENTION]: the 5R55E transmission fluid temperature is available over OBD-II. Requires X-Gauge to be programmed though. Does the 4R70W not have a sensor I wonder?

oh yeah good call... i have the v8.. so no my tranny didnt have one. but i guess yours did.. kinda forgot about the two trannys.. also i have an ultra gauge not scangauge.. mine is the cheaper option which might affect things but i doubt it because when i click trans temp it just says "not supported by your vehicle"

 

[Excalibur07]

OK guys well thanks for all the good replies. It looks like the consensus is that of course the engine temp does go up but the gauge just stays in that same spot unless/until it gets to a critical point. I will check it when I go up there this year - and I think I will get on oe those infrared thermometers from Harbor freight to check it with as well. Can't have too many toys/tools! Maybe I'm just lucky but I have had zero problems - it's feels odd sometimes to be towing my heavy boat up that grade while passing mini vans on the side of the road that are overheated or dripping tranny fluid or on fire - while they are not towing anything!

 

[1998Exp]

The 4R70W does have a temperature sensor - pin 5 on the connector. And it is accessible over OBD-II.

[QUOTE [MENTION=180726]pbnj22[/MENTION]: the 5R55E transmission fluid temperature is available over OBD-II. Requires X-Gauge to be programmed though. Does the 4R70W not have a sensor I wonder?[/QUOTE]