Should I be worried with these temps?

[King951]

A little bit of background. 71 C20 stock - 307 - 3 speed column

This is a photo of my truck before I left the job site towards home. A mixed load of carpet / tile / wood / etc. https://imgur.com/a/pwYMp

My truck has a new 195 thermostat in it. I do not think a lower temp thermostat would help in this situation, I actually think it would make things worse. When I am driving down the highway at 50-55 MPH the truck will stay at 195 +/-5 degrees all day long. I typically leave work around 2 PM and am able to avoid most SoCal traffic but with Thanksgiving coming up, today it was unavoidable. I was in a situation where I had a decent size load in the back, it's about 95 degrees outside, I am in bumper to bumper traffic for 10+ minutes going up an on-ramp. I slowly watched my temperature gauge from about 195 to about 230-235 before I was able to get moving again. Within a few minutes of back at highway speed it was able to get back down to ~195.

The reason I do not believe a lower temp thermostat would help here is because I feel as though most people don't understand how a thermostat works. A thermostat's job is to regulate temperature - period. When your engine is getting hot like mine was (30 degrees over thermostat rating) this means your thermostat is wide open. This would be good and cooling the engine but a wide open thermostat is not giving the coolant enough time in the radiator to cool down - combined with the fact that you are not moving (not getting cool air through the radiator) causes a never ending stream of water that just keeps increasing in temperature. If I had a 180 thermostat it also would have gotten stuck fully open, just at a much sooner rate, which is why I believe it would actually be worse in that situation.

My question is, how bad is it for the engine to occasionally hit temperatures that high? What could be causing this?

Any input / feedback is much appreciated.

[Mr Handy]

first thing I would check is timing. a little more timing may help. I have a 350 with manual trans and this summer in traffic the truck would sit on the 180 stat. only time I go above the 180 mark is with sustained rpms above 2500 and we are talking 7-10 degrees. I think the hottest my engine got this summer was 192* and it was a 95* 90% humidity day and I was blasting 75mph for 20 miles with the AC blasting. pulled off on my exit and dropped to 180 waiting in the light.
if timing does not help its time to look at the fan/schroud. After that it the rad itself. I run a 4 row rad with a 7 blade clutch fan. basically factory hd cooling system.I'm running vintage air ac not stock if it makes a difference.

lean mix will also cause you to run hot, pull a couple plugs and take a look.

[Stocker]

Are you sure that your readings are accurate? Factory gauges are often just a guess, and sending units can leave something to be desired....

That said, if you're running a pressurized system in good working order, with reasonably fresh 50/50 antifreeze mix, you're still safe at those temps. Nothing should be boiling out.

I like to have these basics: Sealed system (takes a correct rad. cap) with a coolant recovery tank. This keeps the radiator completely full, and any coolant lost on hot shutdown will be recovered. Proper fan shroud is a must. HD fan clutch with a six or seven blade fan (if you have a flex fan, send it to the dump). With radiator, hoses, & t-stat in good condition, you shouldn't have any cooling problems.

https://auto.howstuffworks.com/cooling-system3.htm
Fluid - Freezing Point - Boiling Point

Pure Water: 0 C / 32 F - 100 C / 212 F
50/50 mix of C2H6O2/Water: -37 C / -35 F - 106 C / 223 F
70/30 mix of C2H6O2/Water: -55 C / -67 F - 113 C / 235 F

The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point.

The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures.

[King951]

Originally Posted by Stocker

Are you sure that your readings are accurate? Factory gauges are often just a guess, and sending units can leave something to be desired....

That said, if you're running a pressurized system in good working order, with reasonably fresh 50/50 antifreeze mix, you're still safe at those temps. Nothing should be boiling out.

I like to have these basics: Sealed system (takes a correct rad. cap) with a coolant recovery tank. This keeps the radiator completely full, and any coolant lost on hot shutdown will be recovered. Proper fan shroud is a must. HD fan clutch with a six or seven blade fan (if you have a flex fan, send it to the dump). With radiator, hoses, & t-stat in good condition, you shouldn't have any cooling problems.

https://auto.howstuffworks.com/cooling-system3.htm
Fluid - Freezing Point - Boiling Point

Pure Water: 0 C / 32 F - 100 C / 212 F
50/50 mix of C2H6O2/Water: -37 C / -35 F - 106 C / 223 F
70/30 mix of C2H6O2/Water: -55 C / -67 F - 113 C / 235 F

The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point.

The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures.

Looking under the cap it looks completely clear, I am assuming it is straight water no coolant. I topped it off a couple times with water as it was about 1-2 inches low, it then spit out the coolant next stop as I don't have an overflow.

My fan shroud is busted on the bottom half pretty bad. I can go take a photo. Not sure how bad that affects air flow so I just left it. Also, I do not have a vacuum port on my carb so the vacuum advance on the distributor is just plugged off. The timing is set to 5 degrees I believe. (I will check again, was not sure where to set it to.) Also, I do not have an overflow. I fill the radiator up full, next drive it pukes out coolant, and I just leave it as is.

My next steps are gonna be, flush the cooling system and get a good mix of fresh water / coolant, try switching to a 180?, get an overflow, get a new fan shroud, try to get vacuum port on my carb and set correct timing.

[garyd1961]

"The reason I do not believe a lower temp thermostat would help here is because I feel as though most people don't understand how a thermostat works. A thermostat's job is to regulate temperature - period. When your engine is getting hot like mine was (30 degrees over thermostat rating) this means your thermostat is wide open. This would be good and cooling the engine but a wide open thermostat is not giving the coolant enough time in the radiator to cool down - combined with the fact that you are not moving (not getting cool air through the radiator) causes a never ending stream of water that just keeps increasing in temperature. If I had a 180 thermostat it also would have gotten stuck fully open, just at a much sooner rate, which is why I believe it would actually be worse in that situation"

This^ is just completely wrong.

[Stocker]

I agree with your thinking about thermostats (in your first post) so I wouldn't switch to a 180 t-stat. Fan shroud will definitely help. Rather than letting your fresh coolant dump out, I would encourage you to add a recovery tank. It's inexpensive and easy to do, all you need is a place to mount a tank, a few feet of plastic tubing, and a cap for a sealed system and you're good to go.

It's been so long since I checked my timing, I have forgotten what it is. What I have done before is advance it until it pings, then back it down a few degrees. Maybe not the right way but it works.....

So.... what type of fan do you have on that C20? If it has factory A/C it should have come with a clutch fan.

[King951]

Originally Posted by Stocker

I agree with your thinking about thermostats (in your first post) so I wouldn't switch to a 180 t-stat. Fan shroud will definitely help. Rather than letting your fresh coolant dump out, I would encourage you to add a recovery tank. It's inexpensive and easy to do, all you need is a place to mount a tank, a few feet of plastic tubing, and a cap for a sealed system and you're good to go.

It's been so long since I checked my timing, I have forgotten what it is. What I have done before is advance it until it pings, then back it down a few degrees. Maybe not the right way but it works.....

So.... what type of fan do you have on that C20? If it has factory A/C it should have come with a clutch fan.

It is not a clutch fan, just spins along with RPMs at a constant rate. No AC.

[King951]

Originally Posted by garyd1961

"The reason I do not believe a lower temp thermostat would help here is because I feel as though most people don't understand how a thermostat works. A thermostat's job is to regulate temperature - period. When your engine is getting hot like mine was (30 degrees over thermostat rating) this means your thermostat is wide open. This would be good and cooling the engine but a wide open thermostat is not giving the coolant enough time in the radiator to cool down - combined with the fact that you are not moving (not getting cool air through the radiator) causes a never ending stream of water that just keeps increasing in temperature. If I had a 180 thermostat it also would have gotten stuck fully open, just at a much sooner rate, which is why I believe it would actually be worse in that situation"

This^ is just completely wrong.

Could you explain how? I do believe without a doubt a 180 would make my truck run 15 degrees cooler in normal operating conditions, but in the situation I was in I 100% believe a 180 thermostat would not have done me any good whatsoever, perhaps even been worse as the issue would have happened much sooner. If I am wrong I would love to know how as I can perhaps prevent this from happening again.

[harpo231]

could be too lean air/fuel

[Mr Handy]

"Also, I do not have a vacuum port on my carb so the vacuum advance on the distributor is just plugged off. The timing is set to 5 degrees I believe. (I will check again, was not sure where to set it to.)

This is why you are getting hot at idle. No vacuum advance and only 5* timing.
I would set your timing to 10/12* and see how it does. I run full vacuum advance which bumps my initial timing of 10* significantly higher at idle.
what carb do you have that has no vacuum advance port?

don't worry about your t-stat, they set the low operating temp not the high. I like a 180 stat but a properly tuned engine can benefit from 195, this is why modern cars run hotter than our trucks with carbed engines. On the other hand I don't believe in the coolant running through the rad too fast theory either. We are working with heat transfer. Heat travels to cold, it does not care how fast the coolant is moving in a closed system. if the rad cant give off the heat as fast as the engine is making it, you will overheat. If the coolant running to fast through the rad made a difference your rad would be cool when your engine was overheating.

[bcfishon]

It's possible if your fan shroud is bad enough it will allow air to be pulled in where it's broke rather than through the radiator as it's designed. When on the freeway air would be driven in due to higher speeds and will cool you radiator. A broken fan shroud will most likely be a problem at low speeds or when stopped,very similar to a bad clutch fan.

[King951]

Originally Posted by Mr Handy

"Also, I do not have a vacuum port on my carb so the vacuum advance on the distributor is just plugged off. The timing is set to 5 degrees I believe. (I will check again, was not sure where to set it to.)

This is why you are getting hot at idle. No vacuum advance and only 5* timing.
I would set your timing to 10/12* and see how it does. I run full vacuum advance which bumps my initial timing of 10* significantly higher at idle.
what carb do you have that has no vacuum advance port?

It is a Rochester 2G the previous owner said he swapped his old one out for at a carb shop. I have no idea why but every vacuum port on the carb is sealed with what looks like a small steel ball. It looks professionally done. Why they did that I have no idea. I found one big what appears to be 3/8 that I may be able to use an adapter to make it into a vacuum line

[King951]

Originally Posted by Mr Handy

On the other hand I don't believe in the coolant running through the rad too fast theory either. We are working with heat transfer. Heat travels to cold, it does not care how fast the coolant is moving in a closed system. if the rad cant give off the heat as fast as the engine is making it, you will overheat. If the coolant running to fast through the rad made a difference your rad would be cool when your engine was overheating.

But it's not about the coolant running too fast itself causing the issue, it's that the coolant is running too fast to get cooled efficiently enough because it isn't spending hardly any time at all in the radiator. My old truck (67 F100 4x4) had a big block Ford 352 FE that on my drive home I had to pull over a few time because the temperature would start going out of control up to 250 and puke coolant, I would pull over and wait and go again until I made it home. Come to find out the thing had no thermostat in it. New coolant and a thermostat and it never had an issue again.

Go on Google and you can search multiple threads on multiple sites where people complain about removing there thermostat in whatever season and now there car overheats and they can't understand why. Same concept applies to what I am talking about. Why would an engine overheat with no thermostat but be fine with one? A thermostat doesn't just get the engine up to operating temperature it keeps it there by having a combination of holding water back / keeping water in. In the situation I was in earlier today I may as well had no thermostat at all as it would have put me in the same place. Or I may as well had a 180 thermostat as it also would have done the same thing. Once you reach the point where the water coming in is exceeding the temperature of the thermostat that's where the problem begins. That's why I believe my issue had nothing to do with a 195 and a 180 would have done nothing to help. I believe the issue lies somewhere else.

I think getting an overflow, a new fan shroud, set up my vacuum advance and adjust my timing and I will test again from there.

[71cheyennesuperlongb]

Years ago in dirt track cars we always put abig flat washer with a 3/4 inch hole in it to slow the water down. This is what your thermostat does. When it is open it still restricts the water flow enough to provide proper cooling. The only way a thermostat would make it overheat is if it is stuck closed. If you think about it when you are sitting still idleing the water flow is slower than at 50 mph.

[special-K]

A 180 thermostat is what I run. You seem to have another issue, but a 180 t-stat would allow full flow cooling before ever letting your engine get so hot in the first place. I think it would help the situation to a point. That's why I run the 180, a wider margin to boiling.

If it isn't timing or fuel/air mix it sounds like air flow from fan isn't cutting it. I may have overlooked it, but didn't see any talk about fan, fan clutch, or shroud. All those are most important with engine running and truck not moving.