DJB, why is it better for the temp as shown on the gauge to fluctuate as opposed to not fluctuating?

The gauge needle on my wife's old Honda and on her new Honda never move once warmed up. Are they defective?

As I stated before, mine used to fluctuate some depending on ambient conditions and use until I installed the current thermostat. I did absolutely nothing else to the cooling system at the time or since. Logic tells me that the fact that my system temp no longer fluctuates as displayed on the gauge has to do with the thermostat and not to a rigged gauge system.

What am I missing here?

 

Misconceptions!

 

Truly not trying to be confrontational on this particular evening, but what am I misconceiving?

I lived with gauge needles on XJs flopping around for ~28 years and now I've spent one year watching it stay rock steady at one magical point on the '93 gauge. Seems like a winner to me. If it varies from that point, I know something is likely wrong.

In truth, 28 years is not entirely accurate since I don't remember what went on early on with the '85. I know that I finally replaced the mechanical fan with an electric fan in that one to try to make it easier to warm the silly thing up, not cool it down.

Curiouser and curiouser.......

 

Don't think I ever said it was "better" for temp to fluctuate, I just said that's what actual coolant temp does.....it fluctuates. It's obvious the factory doesn't want the gauge to fluctuate, not much any how, as long a coolant temp remains within design parameters.

I think u may have a misconception of what a t-stat does. The t-stat does one thing only.....determine MINIMUM coolant temp. Once the stat opens and driving conditions r such that the stat remains in a "hovering" open position, the stat's job is over and it's doing nothing. At that point (stat hovering open), the rest of the cooling system, it's condition and driving conditions r in total control of determining maximum coolant temp and how much/little the coolant temp fluctuates. At that point, the stat doesn't even need to be in there.

Again, a factory gauge is not likely to show the fluctuations. A digital gauge will.....a digital gauge will show temp increasing within a few seconds of coming to a stop, it will show temp decreasing in a few seconds as speed is resumed from a stop and both air flow and coolant flow r increased. That's just one of many scenarios in which coolant temp will fluctuate.

I don't know how else to say it, coolant temps fluctuate, period. A properly functioning stat has virtually nothing to do with the temp fluctuation, all it does is determine minimum coolant temp. The rest of the cooling system and driving conditions have everything to do with the coolant temp fluctuating because the stat is open and doing nothing.

 

I am attempting to change the thermostat in my 2000 Cherokee Sport and can't get around the serpentine belt. I am no mechanic so I am struggling with this one. Any help would be appreciated

 

The hash mark to the left of 210 is numerically 182.5*. Not knowing the driving conditions and presuming the 180* stat is functioning correctly, a 180 stat would most likely yield a minimum coolant temp a little north of 180....say 185 for example. So if actual coolant temp is 185, but the needle id below 182.5, maybe the dash gauge is not as accurate as u think.

What does a 10* increase look like on the factory dash gauge? The hash marks on the 1st half of the gauge r in 27.5* increments.....the hash marks on the 2nd half of the gauge r in 12.5* increments. Again, the factory gauge may not be as accurate or as easy to read as one thinks.

No, it's not rocket science......rocket science uses extremely accurate gauges/instruments, not ball park like the XJ.

 

Loosening/removing the belt will give a tad more room. Loosen (not remove) the bolt in the middle of the idler pulley at the power steering pump. Turning the adjuster bolt (just behind the belt) counter clockwise reduces tension on the belt. Remember, the bolt in the center of the idler pulley MUST be loose prior to turning the adjusting bolt. After the belt has been properly adjusted buy turning the adjusting bolt, re-tighten/snug the bolt in the middle of the idler pulley.

 

I understand very well how the stat works and have posted exactly what you said above in "overheating" threads in the past.

One of Cruisers good friends from another forum extolled the virtues of the Superstat for years (don't know if he still does). I'm pretty sure that he used to say that it provided some temperature control beyond just open/closed. It's been a long time and I can't swear to that. Cruiser might know.

In any event, why did my gauge fluctuate somewhat before and now fluctuates not at all. I'm truly curious. I drove 100 mi. round trip today partly on the Eastex freeway with legal speeds between 60 and 75. Balance a mix of urban traffic and country highway. Ambients ranging upwards of 100*.

With this thread in mind, I watched the gauge very carefully. Not so much as one tick from the straight up mark we are using as a reference point.

I would truly like to understand this. Surely someone knows the whys and wherefores.

 

When driving in 100* degree ambient, I doubt there will much fluctuation.....if there is a fluctuation, it's probably the needle moving to the right due to the cooling system being maxed out and doing the best it can under those conditions. Again, if the stat is hovering between closed and wide open, it is doing nothing. What should it be doing, when it's open, other than allowing coolant to flow to the rad? The rad is where the cooling takes place. The stat only determines minimum coolant temp by closing off flow to the rad. In 100* degree ambient, u can bet the stat is wide open and again, doing nothing. Cruiser is not a fan of Stant stats, I am though.

 

I guess this is what I was referring to:

"EZ, that's good to know yours fluctuates some.....that's better than our other 2 vehicles that never fluctuate, regardless of driving conditions." I guess this is what I was referring to.

I didn't say that Cruiser is a fan of Stants, just that one of his very good friends is or was.

The hard cold truth is, I doubt anyone gives a FF whether or not my gauge fluctuates, including me. I would like to understand why but I'm finished with the search unless something pops up that grabs me by the YY and won't let go. Or maybe I'll Google it tomorrow...who knows?

 

I don't really understand the fluctuating and dash gauge issue unless the dash gauge behavior has changed over the years.

On my 01 the needle will typically be a needle or two below or above 210F depending on exact conditions. In the summer, if I shut it off and run into a store for a few minutes, it will probably be a bit above 210 when I start it back up. On the highway it usually runs a needle width below 210. If the fan comes on, the gauge will be higher than when it's off.

Maybe the readings aren't 100% accurate, but the readings makes sense.

 

Here's the misconception (djb383's), and you missed it, Pelican.

The thermostat is an active device. It opens and closes in response to the temperature. It's not a binary device, either. It's not ALL OPEN or ALL CLOSED. It is one part of a system that regulates temperature. If it's doing its job correctly, and if the heat load stays within the design parameters, it will keep the temperature at a steady state.

Of course, it is just one component, and it has limits to what it can do.

If the heat load is such that the thermostat is wide open, that's it. That's all it can do. Your temperature will climb at that point.

In normal conditions, within the operating range of the thermostat, it will open and close PARTIALLY to keep you at a steady temperature.

 

As far as the dash gauge being rigged to display a temperature that may or may not be accurate to keep the driver happy, I'm still going to go with inconclusive. When I was running real hot, the dash gauge didn't go beyond the 220 mark, but Torque Pro app + bluetooth OBDII dongle showed a reading of 243 degrees. Obviously way too hot. Now that I've stabilized my cooling issues, I still believe that the dash gauge is fairly accurate within normal operating temps (up to 210ish)

I've remedied it by implementing a fan override switch with a relay so that the PCM can still control it when the switch is OFF. Turning the fan on right around 200 degrees manually on a hot day seems to really help keep it stable. Also, as of last night, I installed a transmission cooler I got from a 91-94 Ford Exploder at the junkyard for ten bucks. I also did a total flush with new Dex/Merc III. Before the cooler was installed, on a hot day, I recorded a trans temp of 218 degrees. Since driving it last night and to work this morning (some highway driving), the trans is running at a cool 161 degrees, and the engine was running right around 205. So far I think it has been a big help--and yes, I did bypass the radiator. For those of you who read that and are about to say "what about the winter time blah blah blah", I have a plan. you can get a thermal bypass valve that acts as a thermostat for your trans fluid. Win-win. But I will only install one of those after I personally see that all the debate on an overcooled trans has any merit.

 

Where abouts did you mount your cooler?

 

In front of the mech. fan.