It seems that cooling and temperatures come up on here more often than not. There is a lot of information that gets p***ed along, and some of it is good, but a lot is nonsense. I thought I would list some FACTS that people seem to ignore. For some silly reason people seem the think that this 200° is too hot. Some of that thinking comes from days past when cooling systems did not have the ability to keep a motor at 200° - when they got up there they just kept climbing and then they boiled over. Here is what most people overlook. There are two critical things that temperature in the motor effects aside from just the temperature of the coolant. First is the fuel. Low octane fuels need higher engine temperature to burn completely. This will result in more power AND better fuel economy. This is a good thing. temps above 210° will burn so much more thoroughly that emissions will drop significantly and that is why late model car cooling systems are do much more sophisticated than old cars - the manufacturers want the temps to stay right around that 210° number to meet emissions standards, while also increasing mileage. The other thing is one that most people really don't know about and some don't even believe. Higher temps will DECREASE Engine Wear! I'll say it again, HIGHER TEMPS WILL DECREASE ENGINE WEAR! now of course this is again only up to a point. Above 250° wear starts to go back up. Testing has been done to check cylinder wall wear at various temperature in a 60 hour test at each temp. At 200° the cylinder wall wear was negligible, under .0001". At 180° that wear increased to .0005" - a substantial increase. at 160° it went up to .001" (that is a 10 times increase in wear!). For those in the cold climates - a temperature of 50° caused wear of .010" at which time the motor was starting to burn oil. Ideally for our Hot Rods we would like to see and control the temperature between 195° and 205° for the best of all worlds. Thermostats - many folks first response to an engine running hot is "put in a lower thermostat". The thermostat's Primary function is to get the engine up to operating temperature quickly. Cold motors don't run as well and create more engine wear (see above). The thermostat also has some effect on keeping the temperature regulated, but ONLY on the cold side. If the cooling system has a 180° Thermostat and is maintaining the temperature at say 190°, putting in a 160° thermostat will NOT make it run any cooler - It can't. Both thermostats are fully open at this point. There is also a lot of controversy, or differing opinions about running without a thermostat. The arguments for running without are that you remove the restriction and it is one less thing to fail. The arguments for Not running without are that the water will circulate too fast and not stay in the radiator long enough to cool. Naturally the truth lies somewhere in between. Running without the thermostat does not cause the temperature to rise because of flowing too fast through the radiator, the reason the temp can go up is the water will take the path of least resistance and therefore flow mainly around the cylinders in the front of the motor and not circulate well in the rear cylinders, this may or may not cause the temperature to go up on the gauge, depending on where the sender is, but there is little doubt that is causes much more heat in the rear cylinders. When the thermostat is in there, it creates some restriction which causes the coolant to flow more evenly between the cylinders throughout the block. The other reason Not to run without a thermostat is you will increase the speed of the coolant and this can cause friction wear in the radiator, especially in an old car with a lot of rusty contaminants in the coolant. It works like sanding the inside of the tubes and can cause a radiator failure. Radiator Caps - The point of the radiator cap is to keep the coolant in the radiator AND to increase the boiling point. Coolant under pressure raises it's boiling point which allows the coolant to cool the motor without becoming steam. You generally want to run the Highest pressure cap the system will allow. usually the limiting factor is the radiator construction. Some old cars, like the 53-55 F-100's have a radiator upper tank design that will not allow much pressure, 7-8 lbs. is about it. 50/50 mix of coolant and water will boil at about 227° - with a 4 lb cap this increases to 239°, a 7 lb will go to 248°, and 14 lb goes to 263°. Basically for every lb of pressure, the boiling point goes up about 3°. Many Race Cars, like NASCAR will run as high as 32 lbs or close to 300° (but they run pure water, due to coolant being dangerous when it leaks onto a race track) Recovery or Overflow systems - RUN ONE! Old cars didn't have them because they didn't understand the technology. What the recovery system does is makes sure the system stays full of coolant, not air. On old cars, when everything was working properly, if the radiator was full, when you shut the car off it would push some coolant out of the radiator. This was normal as an engine gets Hotter when you first shut it off. The radiator would end up seeking its own level of expansion. The problem was, now you have air in the system. This air space will be compressed when the temperature goes up and that Lowers the boiling point as well as being less coolant to carry the heat out of the engine. A proper recovery system will recover the coolant that is pushed out when the car is shut off, but then vacuum in the system when the motor cools back down will **** the coolant back into the radiator keeping it full and maintaining proper cooling.
Stop making sense, would ya! On my banger A, I often wonder if I get water pushing out the top of the cap (when accelerating only) because with a good water pump and higher rpms, it fills the upper tank too fast. I guess in that case, some type of restrictor would help? Thanks for the info.
great informatiom , thank you very much. My 62 Pontiac Safari runs around 200 degrees , and under load (in drive stopped at the light it will climb 210, 220. I was speaking with my brother and he asked was degree t-stat I had in the car... Which i put in 180 trying to bring the temps down. He suggested finding out what was the factory spec was. To my surprise it was 195... So I put a 195 back in. He was telling me also that it will slow the water down let it cool in the radiator more. I have used Red-Line Water Wetter with some good results.... great information like I said before..
That's great info, but I have some questions. Wouldn't cooling also depend on variables such as high compression engine versus low compression? Wouldn't a high performance engine run hotter than a stock engine? Isn't it true that not all engines are created equal? What works for one, may not work for another? It just seems like everyone has their own formula for effective cooling. If I regulate my cooling for mild street driving, how can my formula work for a guy who drives his vehicles hard? I get that modern engines and cooling systems are efficient and designed to run at higher temps. So my question there would be how? Are the internal parts coated with friction reducing elements? Is a computer needed to control the various systems? In the end, thru experimentation, each person should basically find what works for his car? Not trying to start a **** storm, just wondering if we're chasing ghosts? Maybe there is no universal formula for cooling an older, carbureted engine. Or maybe there is? From what I've read and heard, the "good for all" system would be: aluminum radiator 180degree thermostat 15 lb. radiator cap 50/50 mixture of water and coolant sealed coolant recovery system mild engine compression Yet, for every guy running this setup and getting great results, there are 3 other guys with engines over heating. So, aren't we back to, "Find what works for you and go with that." Again, just trying to gather info and keep this discussion positive and informative.
hmmmmm......... The wear stuff is oil viscosity and part clearance so temp info from a study like there applies only to the specific stuff that was tested. low octane/high octane don't need or want different temps. OEMs spay the fuel against a closed intake valve at low power operation to get better mixing and a higher operating temp helps because the valve just isn't that hot at low power. That is what drives the emission differences. Engine thermal efficiency does go up as engine operating temp goes up because more heat stays in the combustion chamber and cycle efficiency is directly related to operating temp but the ability to actually make hp goes down as temp goes up because the air density and knock resistance are reduced. A 50/50 of coolant is not a great idea mix unless you are in an extremely cold area and need the freeze protection. Straight water or water with a surfactant like water wetter cools significantly better than. YOu need corrosion protection to and just adding some coolant is easy....but 30% is generally plenty. The goal should NEVER EVER be to get the system boiling point up to where engine damage can occur before the system boils. Boiling sets a system max temp (the system temp will not exceed the boiling point until the water is gone) and is a very obvious driver alert that something has gone wrong so the last thing in the world you want is a system that can get into a danger of damage region without any hint something is going wrong. If you aren't sure where that danger region is is then my thought would be stay safe and trust the factory engineers and stick to the factory boiling point. Remote recovery systems are great way to reduce radiator size or allow the radiator to be mounted lower in the vehicle.....but they do not have an inherently better performance. The big space at the top of non-remote recovery radiators is intended to serve the same purpose and does it with less parts and works equally well as a remote version....if you leave a quart of space in it for it to work.
Very good info, thank you. I also wonder about a few points, though. Such as - IF you are running a pre-'70's inline 6 or 8 cyl motor, might it be that sustained temps over, say, 200 deg. maybe gonna warp a head, or block, maybe a manifold? Remember how common it was to blow a head gasket on a flathead V-8 Ford in the summer? Having spent my life in the AZ. desert, it's 106 deg @ the 11 AM reading right now & I am still running a 292 six in my daily driver, I tend to think of such things. So, when I see my temp gage hit 200 because I'm stuck in mid-afternoon traffic, I turn off my Vintage Air & crank down the windows. Long as I'm moving it will stay under that & I'm O.K. I run a 4 lb. cap, BTW.
Fred - yes every motor is different, but they are all just air umps and the logic and theory is applicable to all even if the details vary. Higher compression does indeed generate more heat, but if properly tuned the amount should still be able to be kept under control with a proper cooling system. You'll notice I didn't get into radiator sizing, fans, shrouds etc - that is another whole subject and the more a motor, or vehicle for that matter is modified, the more changes that MAY be necessary to the cooling system to keep up. So many of the topics that come up on here are relatively stock cars that have cooling issues. many times it is as simple as too much corrosion in the radiator and block from years of abuse. The idea here was basic principles to follow when looking at cooling issues.
I've also seen tests as someone noted...NOT ALL engines require the same temps. for the noted results..! Also not noted, is that "anti-freeze"...does NOT do anything for cooling. Infact, it actually hampers it to a some amount. I've been running a 25% (a-f to water) mix for many years with no negitive results, but a cooler water temp., both bikes and cars. Mike
There is: aluminum radiator of adaquate size use a shoud use an electric fan if possible (I know.... but they are better) use a thermostat, what temp depends a bit but 180 is generally a safe choice 15 lb. radiator cap 30/70 max mixture of coolant and water here's an article with the basics: http://www.carcraft.com/howto/ccrp_0707_high_performance_cooling_system/viewall.html I'll go away now.
You have certainly made some valid points, but I pretty much have to disagree with that last statement. the motor water and less air that you have in the system will be more efficient at cooling that a large air pocket in the radiator. The air can "aerate" the coolant decreasing it's efficiency and the larger amount of coolant will do a better job of removing heat from the motor. early Mustang's and Falcon's are a prefect example of this. They had marginal radiator size and cooling ability stock. As those cars have gotten older and more performance has been added to them, the system regularly is unable to keep them cool. I have solved this problem numerous times by just adding a recovery system with the proper type of radiator cap (that allows the coolant to be ****ed back into the radiator) and a little higher pressure. I am a firm believer of this and can't think of any car that has been produced in the last probably 30+ years that hasn't had a recovery system (although I'm sure someone will provide an example outside the norm), and if they weren't a benefit the OE's surely wouldn't spend the money on installing them.
"Running without the thermostat does not cause the temperature to rise because of flowing too fast through the radiator, the reason the temp can go up is the water will take the path of least resistance and therefore flow mainly around the cylinders in the front of the motor and not circulate well in the rear cylinders" Hotroddon, I agree to a point. I am of the opinion that the reason an engine can overheat when the thermostat is removed is that the higher flow reduces the pressure at the inlet of the water pump causing cavitation. In engineering terms the net positive suction head is low enough to create vapor bubbles in the eye of the pump impeller. As has been mentioned several times in this thread there are enough variables in cooling systems that even ones that appear to be identical, aren't. As a result writing a formula that applies to all systems is not practical. That said this is the most informative dissertation on automotive cooling systems that I have seen, thanks.
Yep, topic related questions over & over, especially with Summer high temps now. It is great that those with the backround and knowledge share that info. some people know every detail about their engine. some people are like me that have a ride that has been purchased with only basic motor details. so, trying to figure out cooling, etc can be a shot in the dark.
Higher compression lowers EGT and heat rejection into the cooling system because of the higher expansion ratio. While peak combustion temperatures are higher the amount of heat transferred to the water jacket is lower because the greater expansion makes for lower temperatures in the cylinder during the last part of the work cycle. Going to 9 to 1 engines from 15-1 caused us to melt plug wires and anything else near the headers and run hotter.
Fair enough Is the falcon a top tank or side tank? On a side tank the core effectively gets smaller when the water level drops and thats a very bad thing. I was thinking top tank where the core is fully covered either way but they dont cool quite as well as a cross flow and OEMs HATE top tanks these days because it forces the hood higher and that drives fuel mileage down. I ***umed the hood line was the main driving factor followed by a cost reduction because the plastic remote tank and cross flow let them reduce the radiator size/cost ..but I could be completely wrong here. I use remote tanks on all my stuff BTW so I dont disagree that its a good idea. To me it means I can fit a bigger better radiator and Ive just never found myself wishing Id used a smaller radiator .....
Thermostats are needed to slow the water/coolant. The stat will close holding coolant in the block so it may pick up the heat. Once the stat opens it flows to the radiator were it is stopped by the stat closing as the cool coolant in the radiator p***es over it. The process starts again. However, the stat will stay open all the time as the heat conditions warrant this. In doing so the stat slows the coolant so it my capture heat in the block and cool in the radiator. Race cars in the past would not run a stat but use a large washer with various size holes depending on how the driver wanted his engine cooled.
Okay, I pretty sure my questions got answered. The 50/50 mix ratio is what has been told and written for what seems like forever. Now, I'm hearing 30/70. That's fine and the reasons stated make sense. Currently, I'm running about 50/50 coolant, a 160 degree thermostat, 15lb pressure relief valve on my 2 core, aluminum radiator* with a 20oz recovery tank. At cruising speeds, my temp is about 170-180, which I think is pretty good. BUT as soon as I get at a stoplight for more than a couple minutes, my temp rises to 200+. Now, I'm not running a shroud, but I'm getting one soon. I'm hoping that cures the over heating. My conclusion is that, if my system is cooling while cruising, my overheating is due to lack of air flow. Is there anything I'm missing? * My radiator is from Speedway. It's designed like a stock Model T, in that it doesn't use a pressure cap. It uses a 15 lb. pressure relief valve instead.
For sure the EGT temps go down as CR goes up......but I'm not sure heat into the coolant always goes down because heat is transferred much faster at high temps than at lower temps, so I'd think most would of what is going to transfer would have already transferred long before the temps drop due to expansion???? But depending on head design, a good amount of heat can end up in the coolant for the exhaust port cooling and that would be worse at low CR so maybe that???
What about engine bore size 30 over - 60 over, the exhaust system , the intakes what does this do to the temps ?
Correct you absolutely need a shoud and that will mkae a big improvement..... but while it's maintaining a safe temp while cruising it's not maintaining your set point so you're radiator size is ok but marginal. If you drove hard you'd probably see temps you don't like. A larger would get the in motion temps down to your set point and make the fan's job easier so if the fan alone doesn't solve your problem you might want to take a long hard look at the radiator and what can be done to up size it. As long as the system runs at 15psi the effect is the same.....a 15psi cap just a cheap easy way to build and install a relief valve.
FYI... Radiators with a top and bottom tank are a different animal versus cross flow/ side tank. Down flow radiators top tank acts, ( as you stated ) an expansion tank. I doubt you will ever achieve it being full. It need air to work. SO on a properly working system, once the coolant level settles, it should never spew out...Unless there is a problem.
Thinner cylinder walls transfer more heat into the coolant because they are better conductors. A LOT of heat leaves the engine in the exhaust, so a system that does a better job getting the exhaust out of the engine will mean less heat left to go into the coolant.
mk e, I actually do drive kind of hard. That's my version of cruising. I NEVER drive the speed limit. I'm always 10 to 15 mph over. When I'm on the freeway, I'm driving freely (fast). I jack rabbit start and in general, do everything a persons NOT supposed to do for efficiency. So, I'm not expecting miracles, just consistency. What chaps my *** is, when I first built my car, I had a Superior radiator. That damn thing NEVER got over 180, without a shroud. Problem is, it was for a '31 shell and they don't make a nice radiator for a T shell.
Well it sounds like you already know EXACTLY where the problem is ......but a shroud should help. Mark
Question what about elect fans does it matter if its a pusher or puller ? And I have seen people run both when I ask the guy why he said if he had the AC on or was in traffic or stopped for anytime he turned both on.Now does that make any sense ?
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