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Old 09-09-2021, 12:28 PM
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One thing to consider is that all Pontiac are not created equal when it comes to cooling. Radiator surface area is a game changer! Making a radiator thicker is diminishing returns. The older cars have really small surface area radiators (Not good).

One thing that handicaps new car mileage is weight. All the crap that we can't live without these days. My '01 Saturn SL2 would knock down 34mpg while running the crap out of it and 80 mph on the highway. But it was a tiny, light, car. Those 1.9's are great engines! Just better watch the oil when they get over 100k!

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Old 09-09-2021, 01:17 PM
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Thanks for the suggestions Tom, JSchmitz.

Dad put 500 miles on the odometer after finishing the restoration, and I've put about 500 on it. Total rebuild of the engine by an engine guru near home, so the coolant is "old" (2016) but not very used (mileage). Based on that guru's reputations, I'm willing to assume that the water pump impeller clearance is correct as I've read that can cause poor flow. The radiator is filled up just enough to cover the core, so I know there's at least plenty of coolant in there. I'll start with testing the temp sensor and maybe the t-stat. Flushing the cooling system wouldn't be that hard for me either if it might help.

How important is a 50:50 mix of coolant and water to the cooling performance?

Does the age of the coolant (going on 5 years now easily) make a difference?

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Old 09-09-2021, 01:19 PM
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Originally Posted by JSchmitz View Post
One thing to consider is that all Pontiac are not created equal when it comes to cooling. Radiator surface area is a game changer! Making a radiator thicker is diminishing returns. The older cars have really small surface area radiators (Not good).
Curious.... by "small surface area" are you referring to total surface area across all of the fins, or are you talking length x width of the radiator? I see a lot of cars at cruises that have (what I believe to be) after-market radiators that are much wider than mine. Not really interested in making those kinds of mods, just need to learn.

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Old 09-09-2021, 01:45 PM
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Originally Posted by 64cabro View Post
Curious.... by "small surface area" are you referring to total surface area across all of the fins, or are you talking length x width of the radiator? I see a lot of cars at cruises that have (what I believe to be) after-market radiators that are much wider than mine. Not really interested in making those kinds of mods, just need to learn.
Frontal area. Length and width vs thickness. In '68 Gm cars they got quite a bit bigger (Correct me if I'm wrong in my generalization here). The rear rows on a "four core" aren't doing much. The air is blazing hot by the time it gets through. much better to have a larger frontal area.

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Old 09-09-2021, 01:58 PM
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Thanks for the suggestions Tom, JSchmitz.

Dad put 500 miles on the odometer after finishing the restoration, and I've put about 500 on it. Total rebuild of the engine by an engine guru near home, so the coolant is "old" (2016) but not very used (mileage). Based on that guru's reputations, I'm willing to assume that the water pump impeller clearance is correct as I've read that can cause poor flow. The radiator is filled up just enough to cover the core, so I know there's at least plenty of coolant in there. I'll start with testing the temp sensor and maybe the t-stat. Flushing the cooling system wouldn't be that hard for me either if it might help.

How important is a 50:50 mix of coolant and water to the cooling performance?

Does the age of the coolant (going on 5 years now easily) make a difference?
Pure water is best (with a little surfactant to break surface tension) for heat transfer. Maximum freeze protection is 50/50 I believe.

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Old 09-09-2021, 02:12 PM
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Originally Posted by 64cabro View Post
only recently started paying attention to the temp gauge. On the day that raised concern a week or so ago when I decided to pay attention to the temp gauge and it was around 220 degrees
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Originally Posted by Tom Vaught View Post
1) I would verify that the temp gauge is truly reading 220 degrees F.
More to the point, make sure the engine is actually at 220 when the gauge says it is. It's easy and common for both the sending units and the gauge heads to be inaccurate.

A non-air-conditioned vehicle that's actually running 220 at idle or cruise, is getting too hot. Not hot enough to cause damage, but hotter than a properly-functioning engine and cooling system should get. If you had a 195-degree thermostat, it'd be running too hot. Most likely, you've got a 180, and maybe a 160 degree thermostat, and 220 is just nucking futs.

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Originally Posted by 64cabro View Post
Dad put 500 miles on the odometer after finishing the restoration, and I've put about 500 on it. Total rebuild of the engine by an engine guru near home, so the coolant is "old" (2016) but not very used (mileage). Based on that guru's reputations, I'm willing to assume that the water pump impeller clearance is correct as I've read that can cause poor flow.
I would not want to make assumptions.


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Originally Posted by 64cabro View Post
The radiator is filled up just enough to cover the core, so I know there's at least plenty of coolant in there.
Does this vehicle have a coolant overflow jug? If so, the radiator should be filled to the top, and verified to blow the excess into the jug when hot--and then recover that coolant back to the radiator when the engine cools off.

In other words, the coolant level in the overflow jug would vary--highest when hot, lowest when cold, with the radiator being F-U-L-L 100% of the time.

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Originally Posted by 64cabro View Post
I'll start with testing the temp sensor and maybe the t-stat. Flushing the cooling system wouldn't be that hard for me either if it might help.

How important is a 50:50 mix of coolant and water to the cooling performance?

Does the age of the coolant (going on 5 years now easily) make a difference?
50/50 coolant makes enormously less difference than some folks want to admit. They'll be quick to tell you that plain water transfers heat better than "antifreeze"; but if the difference between running at the correct temp, or running too hot depends on the ratio of antifreeze to water, SOMETHING ELSE IS WRONG.

I've run as much as 80% antifreeze. My engine didn't overheat.

"I" would be very reluctant to replace 1000-mile coolant without a very good reason. Yeah, it's at the limit for age; but that also assumes use which your vehicle doesn't have. Point being, it's not the age of the coolant that's causing the engine to run hot.

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Old 09-09-2021, 02:14 PM
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So C.A.R.B. began in the late 60s, EPA in the early 70s, and we all know what happened to performance in the 70s.

What bothers me most these days is MPGs. Why do new cars suck gas? The tech is there, these econo cars should be over 60 MPG. Shoot, some of the 60s and 70s car get better MPG than some new cars. Not even going to bring trucks into this topic, it's just ridiculous what MPGs they get.



.
Arent newer cars significantly heavier? Not that I dont agree that they should be doing better on mpg than they are. Pickup trucks are especially embarrassing. My standard short box 2017 ram gets 19 mpg and weighs 6000 lbs. But I think many econoboxes of yore weighed notably less than todays cars. Mostly safety stuff, and i dont think anybody would argue that modern cars are safer in an impact.

Im always surprised that hybrid technology hasnt affected more car models. The industry wants to just straight to electric, but it always seemed to me that we could make hyrbid motors much more efficient and take our time getting the entire nation/infastructure ready to go full electric.

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Old 09-09-2021, 03:03 PM
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Originally Posted by 64cabro View Post
Curious.... by "small surface area" are you referring to total surface area across all of the fins, or are you talking length x width of the radiator? I see a lot of cars at cruises that have (what I believe to be) after-market radiators that are much wider than mine. Not really interested in making those kinds of mods, just need to learn.
That makes a lot of sense! Thanks for clarifying like you did.

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Old 09-09-2021, 04:09 PM
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I know you live in FL but on your coldest days with the heater blowing, what temperature does it run? Probably right on your thermostat rating. And now in the summer, the cooling system is no longer able to maintain that temperature. Wouldn't that give you pause for concern?

Sent from my SM-T817V using Tapatalk

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Old 09-09-2021, 05:53 PM
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I realize this thread it old, but I always look for "old" threads before asking a question .... but hopefully I get some feedback.

I'm not Mr. Knowledge when it comes to this mechanical tech, just know enough to know that I need to be careful and not screw something up.... which leads me to question how hot is too hot. I live in Central FL and right now is not necessarily the most enjoyable time to be out hot rodding.... hot air, hot pavement, hot sun, no AC (wha, wha, wha right?)

My Goat has a 455 from 1970 Bonneville. Only had the thing for a few months, and haven't driven it much, but only recently started paying attention to the temp gauge. On the day that raised concern a week or so ago when I decided to pay attention to the temp gauge and it was around 220 degrees and I realized that I have no idea "how hot is too hot" and if I needed to shut it down or not. Reading this thread, I'm somewhat comforted by seeing some of you guys say 220 is OK, but worried when others say 220 is too hot and others talk about driving in AZ and never getting up to 200.

As far as I'm aware, the radiator, fan and pump would be considered stock, though they're all new and rebuilt thanks to a pretty top-quality resto-mod by my dad that he completed a few years ago. "What's wrong with my goat?" is what goes through my mind when I think of why it's not running below 200. I could rationalize that cooler is better, but sounds like that's not NECESSARILY the case.

Looking for dad-type advice on when I need to be concerned, but I'm guessing some answers might include the words "it depends" on X, Y and Z.

Any and all feedback will counted as value and appreciated. Already grateful for the exchange below! I asked dad and he said he can't remember.... he's suffering medically and recalling technical facts and answers like he once could is no longer his strong suit....unfortunately. He did suggest I turn to the forums to read up and ask questions!
If mine got in the 220 range I would be VERY nervous…. And I live not far from you. Better a little Cooler than hot in my book. Ambient temperatures WILL make a huge difference.

fWIW:
I generally creep to 180 at maximum while in traffic at a standstill with 90-100 degree ambient temps on a hot FL summer day…. Temps will drop to thermostat temps with the car moving again. When ambient temps start dropping to the 80 degree range the engine will stay at tstat temp

Chasing cooling temps can be a hobby until you find what works…….waaaaaaayyyyy too many variables especially since you are living in a hot and humid environment, your cooling system needs to be well sorted.

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Old 09-13-2021, 07:12 AM
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More to the point, make sure the engine is actually at 220 when the gauge says it is. It's easy and common for both the sending units and the gauge heads to be inaccurate.
I tested the gauge and probe by putting the probe in boiling water (used a portable induction surface right there in the engine compartment) and the gauge was right on 210 when the water was boiling. In my book, that's plenty good. I'll just need to pay closer attention next few times I'm out to see what's going on. Maybe it's all in my head and nothings wrong, just want to be cautious rather than sorry.

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Old 09-13-2021, 07:19 AM
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I know you live in FL but on your coldest days with the heater blowing, what temperature does it run? Probably right on your thermostat rating. And now in the summer, the cooling system is no longer able to maintain that temperature. Wouldn't that give you pause for concern?

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Yes, it would. GTO came from Ohio to FL in April, so I have no idea what temp it runs when it's cold down here. I'll have to wait for Jan/Feb to test that one. Hopefully by then I have a handle on this, IF there really is a problem. I need to do some close-to-home driving and really pay attention to what's going on.

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Old 09-13-2021, 08:06 AM
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I tested the gauge and probe by putting the probe in boiling water (used a portable induction surface right there in the engine compartment) and the gauge was right on 210 when the water was boiling. In my book, that's plenty good. I'll just need to pay closer attention next few times I'm out to see what's going on. Maybe it's all in my head and nothings wrong, just want to be cautious rather than sorry.

EXCELLENT step 1 verification... proof gauge is showing you real data (really close anyway)

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Old 09-13-2021, 10:04 AM
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I use a 160F thermostat in non-computer cars and Judge runs under 180F even on hot Florida days with the AC on. Four core radiator, water wetter, 7 blade clutched fan, and a close fitting shroud. Warmed over 400/Muncie.

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Old 09-13-2021, 10:32 AM
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With a 190f thermostat I am thinking the larger differential in ambient temp and a hotter engine temp, the cooling system should be more efficient. What do you think?
Running a hotter engine is never a good idea. You should leave it alone.

The only reason that the engines were made to run that hot was for emissions. A cooler engine makes more power, and has more longevity. Heat makes metal more malleable, which increases the wear rate.

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Old 09-14-2021, 05:30 PM
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Originally Posted by 64cabro View Post
I tested the gauge and probe by putting the probe in boiling water (used a portable induction surface right there in the engine compartment) and the gauge was right on 210 when the water was boiling. In my book, that's plenty good.
I'll accept that as the gauge and sender being accurate enough.

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Originally Posted by 64cabro View Post
I'll just need to pay closer attention next few times I'm out to see what's going on. Maybe it's all in my head and nothings wrong, just want to be cautious rather than sorry.
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Originally Posted by Schurkey View Post
A non-air-conditioned vehicle that's actually running 220 at idle or cruise, is getting too hot. Not hot enough to cause damage, but hotter than a properly-functioning engine and cooling system should get. If you had a 195-degree thermostat, it'd be running too hot. Most likely, you've got a 180, and maybe a 160 degree thermostat, and 220 is just nucking futs.
SOMETHING is wrong, or your engine wouldn't be at 220 during idle or cruise. 220 at heavy throttle for short periods of time doesn't worry me, assuming it drops immediately when you close or mostly-close the throttle (idle or cruise.) 220 fairly constantly means there's problem(s) you haven't found and fixed yet.

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Running a hotter engine is never a good idea. You should leave it alone.
I say he should find the problem that's causing excess temperature at idle or cruise.

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Originally Posted by Navy Horn 16 View Post
The only reason that the engines were made to run that hot was for emissions. A cooler engine makes more power, and has more longevity. Heat makes metal more malleable, which increases the wear rate.
Emissions is a reason to put a higher-temp thermostat in the cooling system. OEM applications may not turn the electric fan on until 220 or so, and the second fan may not come on until the engine is even hotter.

Within reason, higher temps INCREASE engine life. "Malleability" is not a concern, detonation could be.

But 220 at idle or cruise isn't "within reason" for this vehicle. There's no problem for engine life per se due to the temperature, but power output will be down, chance of detonation could increase, and the detonation could cause engine damage.

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Old 09-15-2021, 03:14 AM
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Manufacturers have had 50+ years to sort out their cooling systems. We might say that they were still learning when our cars were made. The temperature reading is an average of coolant from cooler and hotter internal passages in the engine. A 220° thermostat reading is an average of say 200° coolant and 240° coolant (or even a greater spread). Personally I feel much better if my average is a combination of 160° and 200° showing 180° on a gauge. Newer vehicles with aluminum heads and some with aluminum blocks do a much better job of distributing heat and the temperature spread coming up to the thermostat is much better controlled and they can bump the overall average operating temperature higher.

An example of temperature spread would be coolant that goes from the block to the head at the front inside of the engine block/head is going to be much cooler than coolant from the passage going into the head on the outside passages near the two center exhaust ports of the engine.

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Old 10-09-2021, 01:40 PM
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After a month of delays (life happens) I was finally able to play with the '64 this afternoon. I ran it @ idle in my shop, started with the radiator cap off. Water was a touch over the fins inside and stagnant until somewhere around 160 then it started moving around a bit, then a few minutes later it was flowing pretty good. Put the cap back on and let it run and seemed to stabilize around 180. That was pretty satisfying to see. Total idle time was about 20 minutes.

I then took it out for about a 20 minute drive, not horsing around much just 40-60 mph driving and it ran pretty steady around 190, climbed to 195 at a long light, then back to 190 when I got moving. Ambient air temp was mid to high 80s. All that said, I feel pretty good about the temp now. I'm going to assume everything is OK and that I don't need to mess around with the other suggestions, but will be sure to keep an eye on that gauge. The more I get used to seeing where the temp (and other gauges) are at on a normal basis, the better off I'll be. Thanks for the help.

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Old 10-09-2021, 03:55 PM
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Originally Posted by 64cabro View Post
After a month of delays (life happens) I was finally able to play with the '64 this afternoon. I ran it @ idle in my shop, started with the radiator cap off. Water was a touch over the fins inside and stagnant until somewhere around 160 then it started moving around a bit, then a few minutes later it was flowing pretty good. Put the cap back on and let it run and seemed to stabilize around 180. That was pretty satisfying to see. Total idle time was about 20 minutes.

I then took it out for about a 20 minute drive, not horsing around much just 40-60 mph driving and it ran pretty steady around 190, climbed to 195 at a long light, then back to 190 when I got moving. Ambient air temp was mid to high 80s. All that said, I feel pretty good about the temp now. I'm going to assume everything is OK and that I don't need to mess around with the other suggestions, but will be sure to keep an eye on that gauge. The more I get used to seeing where the temp (and other gauges) are at on a normal basis, the better off I'll be. Thanks for the help.
What did you do to make it run cooler?

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Old 10-09-2021, 05:02 PM
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What did you do to make it run cooler?
Really nothing. It's hard to explain why I had the 220+ temps when I posted originally.... but at the center of it all was a loose radiator cap.... need I say more?

I suffer from "rectal cranial inversion" sometimes and that's the best explanation.


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