What's the normal heat range fluctuation?

Zezima

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Driving a 71 383 2 barrel, and the other day I was driving it, the temp gauge seemed pretty consistent, hovering around 40%, if we consider C on the left to be 0% and H on the right to be 100%, and the center to be 50%. The temp gauge works, and the readings are consistent, so I trust its movement, I'm just curious how much I should be concerned when it does start leaning slightly to the right under certain circumstances. I've noticed today it's a lot more frequently tending to more around the 60% area, and occasionally seems to even lean almost to the 70-75% range. It does seem to run a little bit hot, but I'm not sure what would be causing it or how worried I should be. I was told that the way the Polara's temp gauge works, with 4 markings: 2 on the outside extremes, and 2 on the inside which indicates operating temperature range, that as long as it's in that range it's fine, and the Polara manual says the temp gauge should be centered, but I don't know if I should be looking at my cooling system or not.

I haven't yet been able to determine the exact causes of when it'll start leaning hot, since some of those instances, such as coming to a red light, it doesn't, so I haven't been able to intentionally reproduce it yet, but it happens fairly often now where it ran noticeably, if only slightly cooler before. I just want to make sure it's running optimally and smoothly and no damage is being done. I've also noticed, although I'm not 100% sure it's related, that after it had a minor overheating episode where there could be heard the sound of coolant boiling if you had the hood open and you were listening, which might have been due to an air bubble, that it started running slightly rougher since then. Not a big difference, and I don't think most people would notice, but it did used to run perfectly smooth and solid before, now there's more vibrations at idle for example. Possibly misfire?

Just wondering what everyone's thoughts were.
 
If the car was overheating at some point, then you might need to change the spark plugs. I would take a few out and look at their condition.
 
I asked a similar question recently and the best answer I got was that the gauges are non-linear. In other words, “halfway “ doesn’t necessarily indicate 50% of some scale that goes from one certain low temp to a certain high temp.
I have owned many of these era Mopars and have always considered their temperature gauges to be “dramatic”. That being said, when they start riding above halfway I get concerned as well. I believe your situation warrants further investigation.
 
hovering around 40%
good.
the 70-75% range.
definitely not good. these are handy. scan the area around your thermostat.
71uVI3koJyL._SL1500_.jpg
 
If the car was overheating at some point, then you might need to change the spark plugs. I would take a few out and look at their condition.
Not correct.

The "heat range" of a sparkplug allows for selecting a plug for a given engine's carb/richness/cam/chamber design/etc/etc that is hot enough to burn away carbon deposits to prevent fouling, but not so hot that it causes preignition like a diesel's glow plug. That's it. The massive combustion heat that emanates from the chamber and down the piston cares little about the heat flow up that insignificant plug. All that heat is the responsibility of the cooling system.

But in a related issue, an engine jetted too lean can cause slightly higher temps, and then you'd want a cooler plug to avoid preignition...which is a variation on the same combinations of "stuff" that I've outlined above.

As for those slightly higher temps? A properly functioning cooling system can handle much more heat that a engine loafing down the road at 65 puts out. The big heat comes from long, hard acceleration, and the cooling system is sized to handle those loads.
 
I did not mean that the plugs caused the overheating. I meant that the overheating may have damaged the plugs and that is why it may be idling a little rough.
 
Well ... I don't know if this has happened to you fellas before, but it seems I have ants in the coolant. Like filled with them.

20230525_145927.jpg
 
I've never seen anything like that before. Do you think they were attracted to the smell of the antifreeze?
It seems like it's common for sugar ants to be attracted to antifreeze.

Though as far as the overheating investigation goes, it seems it's a bad thermostat that would sometimes get stuck off and on, which is why it would run cooler on some days than others. Hopefully replacing the thermostat brings the majority of the temp control back in line.
 
Well ... I don't know if this has happened to you fellas before, but it seems I have ants in the coolant. Like filled with them.

View attachment 598809
Nature’s version of stop leak? Also clogging up the radiator?

Actually they look small enough to flow through. Make sure your radiator cap seal is clean in case these gritty little suckers are coating the seal allowing leakage.
 
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