How hot is too hot?

[Tonz]

Hi all,

My 26 Chrysler 50 four is steadily running up some miles now and all seems to be going well and happy cruising on 35mph.

Which has got me asking about the running temp of the engine, my capillary temp gauge always sits on 190°f. I've backed it up using a temp gun.

The car seems to be happy and making good power. Either idling in traffic or going up long inclines seems to make hardly any difference.The coolant will usually purge down to the baffle plate about 2" under the filler cap. 

Bearing in mind it's an unpressurized, no thermostat, no water pump thermosyphon motor, is that an average summer running temp for these period cars.

If you're running a thermosyphon car I'd like to hear how you car runs. Please don't confuse topic with any info about pressurised pumped systems.

Cheers.

 

[Fordy]

Its not boiling. I fitted an electric water pump to one of mine. Its designed to run on 12 Volts but I run it on 6. With it off the car gets to around 185-190, switch the pump on and plummets to just over 100 (measured on the outlet from the head.)

 

[Mark Shaw]

Old cars run better hot (just before they boil over).  If it doesn't boil, leave it alone.

[Oldtech]

I agree with mark. Thermosiphon systems tend to self-regulate. If it never boils, be happy. 

[Rusty_OToole]

Some owners of 20s cars and motorcycles report that they run better and cooler if they add a little kerosene to the gas, 10% or 20%. Gas back then was oily, and much lower octane than today's. The heavy ends slowed down combustion and gave more power in a low compression engine.

[R Walling]

 I have often wondered why 212-220 degrees is to hot to run an engine.

 Just because water happens to boil at that  temperature

 

 Does the cast iron care how hot it is?  Or do the bearings fail at 212?

 

 Serious question, does anyone have an answer? 

[Barney Eaton]

I agree with "as long as it doesn't boil"     I had a '39 Buick (last year Buick without pressurized cooling) and

originally would fill it up to the filler neck.    The experts informed me the system needed room to expand and 

if you overfilled, it would be pushed out.   

As you know all manufacturers went to a pressurized system and raising the pressure  raises the

boiling point.   Early on they had 4# pressure caps,  then 7# and I think we are up to 14#

Today they run the engines hot to reduce emissions.   So the answer to one of your questions,  hot does not damage

anything unless you have boiled off the coolant.

You might be able to convert your system to pressurized but some of the thing you would need to change would 

change the stock appearance. 

[m-mman]

3 hours ago, R Walling said:

I have often wondered why 212-220 degrees is to hot to run an engine.

 Just because water happens to boil at that  temperature

In a non pressurized system any boiling turns the water into steam vapor that can easily leave the unsealed, open system, meaning that there is less "water" in the system and the system needs to be refilled. (the common filling station task) 

Steam escaping would be the equivalent of a leaking cooling system. 

Edited March 2, 2023 by m-mman (see edit history)

[Rusty_OToole]

In the 30s some car makers experimented with a cooling system that worked by boiling the water then condensing it again. It worked fine. Early stationary engines had no radiator, just a water tank and worked by boiling the water away. Modern pressurized systems frequently run at over 212.

 

A thermosyphon system won't mind boiling as long as you top up the water before it gets too low.

[R Walling]

 i WAS LOOKING FOR THE TECHNICIAL REASON THAT 212-220 Is THE OTIMUM TEMP.

[Rusty_OToole]

The hotter the engine runs the more efficient it is, as long as it doesn't overheat, seize or burn up. Modern engines with pressure systems routinely run at 212 or more.

[Barney Eaton]

A quick search of the internet shows a mixture of 50/50 boils at 223 that raises your boiling point

11 degrees over just water.    On a pressurized system each pound of pressure raises the boiling point 3 degrees F

[Mark Shaw]

20 hours ago, R Walling said:

 i WAS LOOKING FOR THE TECHNICIAL REASON THAT 212-220 Is THE OTIMUM TEMP.

Roger, 

You seem to be over-thinking this.  The technical reason is that water was the most cost-effective and readily available coolant used through the 20's in ambient pressure coolant systems.  I think the engineers of the day were not looking for the optimum temperatures for bearings or lubricants.  They probably just wanted the engine to be cool enough to keep running. 

[m-mman]

Best temperature for the metal parts???   Use of water as a coolant of convenience? 

 

This begs the question "What about Franklins?" 

Did the Franklin engineers have metal temperature limits that they were shooting for or striving to avoid? 

[Oldtech]

On air cooled aircraft engines a typical redline is 425 degrees F for the cylinder heads. Above that you start getting oil breakdown. Motor oils may not be rated quite that high but you have some leeway between 180 and 425. It's all a compromise. higher temps mean better efficiency, but water based coolants are cheap and effective.  

[Str8-8-Dave]

On 3/2/2023 at 8:50 AM, R Walling said:

Does the cast iron care how hot it is?  Or do the bearings fail at 212?

The cast iron won't care as long as after the coolant boils off and things get really hot you don't cool it off suddenly.  If we are talking non-pressurized cooling systems 21 is too hot because the coolant will boil off.  At sea level water boils at 212degF, every PSI you can raise the pressure of the cooling system gives you another 3degF before coolant boils.  Bearings won't fail at 212 but if coolant is 212 and you have been running for awhile under load oil temp will be a lot higher than 212.  I'm not sure what critical oil temperature is so won't opine on how hot is too hot.

Edited March 5, 2023 by Str8-8-Dave (see edit history)

[Rata Road]

I have the same running gear in my 27 Chrysler 50. Honeycomb radiator in perfect condition (apparently non honey comb after market ones don't work as good).

An a open road run at 40 - 45 mph it runs at 97 deg C but in town it run less at around 85 - 90 deg C.

When turned off it makes no gurgling sounds or use any water. Running premix anti freeze.

I have had 3 Model T's and two 20's Triumphs, all running siphon system and all run correct with no gurgling when turned off. If the radiator is clean and in good condition the original system is great.

Mind you I dont live in desert heat, never have traffic jams and dont do parades.

[Stude Light]

One thing this conversation lacks is what type of coolant is used.

 

I’ll just offer some facts:

- Water is by far the best coolant when it comes to the ability to transfer heat from the engine to the air passing through the radiator

- Water offers no freeze protection (0 deg C and below)

- Water requires a corrosion inhibitor additive

- 50/50 ethylene glycol has about 60% the heat transfer ability of pure water 

- 50/50 ethylene glycol has about 80% of the specific heat capability of pure water

- 50/50 ethylene glycol has a higher viscosity than pure water which decreases the overall coolant flow rate through your engine 

- 50/50 ethylene glycol boils at 223 deg F vs 212 deg F for pure water (in an open system)

- Converting liquid coolant to a vapor requires the absorption of lots of energy. In other words, boiling your coolant absorbs a lot of heat.

 

That all said, if you can forgo the freeze protection, running water with a corrosion inhibitor will significantly improve the efficiency of your cooling system. So, if you are having issues of running too hot, just switching from glycol to pure water may be your answer even with the lower boiling point as the improvement in efficiency will lower your operating temperature given you have some level of movement of coolant and airflow through the radiator.

 

[nzcarnerd]

On 3/1/2023 at 7:37 PM, Tonz said:

Hi all,

My 26 Chrysler 50 four is steadily running up some miles now and all seems to be going well and happy cruising on 35mph.

Which has got me asking about the running temp of the engine, my capillary temp gauge always sits on 190°f. I've backed it up using a temp gun.

The car seems to be happy and making good power. Either idling in traffic or going up long inclines seems to make hardly any difference.The coolant will usually purge down to the baffle plate about 2" under the filler cap. 

Bearing in mind it's an unpressurized, no thermostat, no water pump thermosyphon motor, is that an average summer running temp for these period cars.

If you're running a thermosyphon car I'd like to hear how you car runs. Please don't confuse topic with any info about pressurised pumped systems.

Cheers.

 

You mention the water 'purging down to the baffle plate. When you top up the water there is no point filling it to any more than just above the visible radiator matrix when you look inside the filler hole.

 

Those old non-pressurised systems carry a lot more coolant than a modern pressurised one. 

[Rusty_OToole]

There is a lot to be said for thermosyphon cooling. I wouldn't have believed it until recently. But, some very smart engineers believed it the best system. Like C. H. Wills. He designed the Model T Ford and later went on his own to make the Wills St. Claired luxury car with overhead cam, V8 and six cylinder engines - with thermosyphon cooling. This proves it was not just for cheap cars like the Model T. Here is Jay Leno testing his newly restored Wills St. Claire which he says, does not overheat even on hot California days.

 

 

 

[Max4Me]

On 2/28/2023 at 10:37 PM, Tonz said:

If you're running a thermosyphon car I'd like to hear how you car runs.

Tonz, I have a 1925 Maxwell/Chrysler (built in Canada after  Chrysler bought Maxwell, but before being totally rebranded), that is basically a Chrysler Four. It has a thermosyphon system. A few years back a person on the Maxwell site had basically the same question, so I did some tests. I live in So. Calif. and at the time of my tests the ambient air temp was about 100º F. After a drive, I used an infrared thermometer to check water temp in the fill opening as well as my wife’s kitchen thermometer directly in the fill opening (oops!😬). Within a few degrees, both thermometers read about 192º. At the return hose at the bottom of the radiator the temp was close to 175º. Keep in mind the temps were checked parked, at idle. I would guess while driving the temp at the bottom probably would be lower because of more airflow. Hope this helps answer your question.

[Stude Light]

2 hours ago, Rusty_OToole said:

There is a lot to be said for thermosyphon cooling. I wouldn't have believed it until recently. But, some very smart engineers believed it the best system. Like C. H. Wills. He designed the Model T Ford and later went on his own to make the Wills St. Claired luxury car with overhead cam, V8 and six cylinder engines - with thermosyphon cooling. This proves it was not just for cheap cars like the Model T. Here is Jay Leno testing his newly restored Wills St. Claire which he says, does not overheat even on hot California days.

 

 

 

Steam locomotives used a thermic siphon design inside their boilers so the design was around well before car engines and seemed to work well.

Edited April 24, 2023 by Stude Light (see edit history)

[28anut]

Thank You to the past 5 or 6 posters who answered this question and each gave an important piece of different information.  In the past, I had a water hose burst and quickly empty the water.  I caught it within a quarter mile and shut the engine off.  I had my laser thermometer with me and checked the temps.  As I remember it was 400-600 on the cast iron, with it the hottest readings near the exhaust ports.  I let it naturally cool down to cold before replacing the hose and water.  I've noticed no ill effects except a couple of paint bubbles where the paint is thick.  With info from Str8-8-Dave and Oldtech my fears of internal damage have diminished.  I do run straight water with anti corrosion, Thanks Stud Light for confirmation of stats.  And to piggy back on great comments on thermosyphon systems, in older postings found elsewhere in the AACA blogs, it was pointed out that a water pump can pump too much water too fast and effect cooling temperatures.  I do appreciate the knowledge that is shared here.

[dodge28]

When coolant temperature gets too high the engine  oil gets thin and oil pressure drops. That condition causes internal engine damage. Subject to correction here,

[Stude Light]

I'll add a couple of other data points to this discussion. When I was a test engineer at GM, we used 250 deg F as the maximum continuous operating oil temperature during extreme operations and 275 deg F as an excursion limit as the oil will start breaking down at temps above 275 deg F.

 

As a helicopter pilot, the air cooled piston engines in the aircraft I flew used 245 deg F as the maximum allowable oil temperature and 500 deg F as the maximum allowable head temperature. The heads were aluminum and integrated to a steel cylinder.

 

Cast iron will easily handle 500 degrees but high temps like that causes dimensional issues (for clearances) and, if oil is contacting that surface, it will immediately break down and then you start getting closer to the autoignition temperature of oil.

[Buick35]

I'm in Florida and not running any anti-freeze in my 35 Buick.What type of anti corrosion do most of you recommend and or water pump lubricant? Thanks.

[Barney Eaton]

I use Prestone water pump lube and antirust.  add it every year to all my cars which all have antifreeze. 

It is getting harder to find any brand on the shelves of auto parts stores so I find it in bulk quantities on Ebey or Amazon. 

 

I live in Texas and all my modern cars with automatic transmissions I add an auxiliary transmission cooler.   This cools the trans 

fluid and also helps the radiator as it is not doing all the work cooling the trans fluid.    On my Reatta,  the auxiliary cooler does all the work, no transmission fluid goes to the radiator.    This will work on cars rarely driven in the winter and in TX if it is below 40 I am not driving it. 

 

Slightly off the content of this discussion..... how hot do you think transmission fluid is if it is cooled by a 180 degree radiator? 

Heat kill automatic transmissions......... 

[JACK M]

20 hours ago, Barney Eaton said:

Slightly off the content of this discussion..... how hot do you think transmission fluid is if it is cooled by a 180 degree radiator? 

Heat kill automatic transmissions......... 

I have often had this very same thought.

[Rusty_OToole]

Transmissions can run too cold too. I have had old cars where the trans did not work right until it warmed up. The cooler in the rad maintains the correct temp. I would add a cooler if I towed a trailer but would not leave out the stock cooler.

[Stude Light]

On 4/27/2023 at 5:17 PM, Buick35 said:

I'm in Florida and not running any anti-freeze in my 35 Buick.What type of anti corrosion do most of you recommend and or water pump lubricant? Thanks.

I have been using No-Rosion for about 8 years now (started with my 1923 Studebaker) and have had excellent results. Most of my pre-war cars are running just water and No-Rosion. My Studebaker has cast iron, aluminum, brass and copper in the cooling system and I have not seen any corrosion in those 8 years. You can also add it to your glycol based coolant to improve corrosion protection. It also has a lubricant additive.

 

https://www.no-rosion.com/

[Buick35]

Thanks,I'll try to get a bottle.

[keithb7]

I will share my own personal experience with engine coolant temps. I'ver been chasing a few demons on my old Mopars, I've worked out a lot and I think I grasp it pretty good now.

 

The cooling system is exactly that, a system. A system of various parts all dependent on each other to cool properly. If you try to fix cooling system overheating issues by focusing on one thing, you'll just keep on adding a band-aid, or continue to struggle. Every component must be looked at and understood. Put your engineering hat on and think about what the part is supposed to do, and what is it doing now? Could it be adding to, and compounding the overheating issues?

 

Assume you have an all stock system. It was engineered and custom built exactly for your stock car. It will dispense heat exactly as needed.  Assume you are overheating. For illustrative purposes only, lets see what might be going on:

 

Lets assume the rad size effects 75% of heat dissipation.  However that is dependent on efficient clean, air low in large volumes getting though the rad. This is a important sentence as their are many variables here. Is the rad externally clean, all the fins allowing air through them?  Are the internal cores of the rad, the water flow passages clean? No rust, scale, calcium buildup in there impeding water flow? Is the fan the stock size, located nice and close to the back side of the rad? Does the rad use a shroud around the fan to control airflow so it pulls the maximum amount of air through the rad? Inside the block, is there a thermostat? Does it work? Does it need a thermostat? Does removing the thermostat make the engine run cooler? Sure on sub zero winter days only. Does changing the thermostat rating make the engine run cooler? Maybe, but only under certain conditions. Not if the thermostat is wide open, if its hot outside its now doing nothing whether the thermostat is 160F or 190F rated. It won't make any difference when things are very hot. There seems to be a lot of confusion around what thermostats do, and why the different ratings.

 

Inside the block there are cast channels for water to flow through. The cooled water is to follow these paths to cool down certain parts of the engine. Especially important in the L-head engines. The valves in the block get priority cooling right from the water pump. What if the block cooling passages are ignored for decades? Tremendous rust and scale builds up. When the engine is shut off, it settles in the lowest part of the block. Over decades it builds up, partially plugging water passages. Then water movement becomes inefficient. Flow is impeded. Little dead spots or back-eddies are created and the water is not moving to the rad here. These areas get hot and stay hot. Assume water flow though the block is down 45% due to blockages. That is a ton of heat staying in your block not being cooled by the rad. If the block is full of crap, chances are the rad is too. So now any water that does make it to the rad, it is slowed down by 40% as it travels through the rad. The system is failing. Unable to do what it was engineered to do, remove heat.

 

Then there's 80 years of previous owners doing funky things to their cars. Is the radiator the stock rad still? Maybe it was swapped out with something else that fit? Is the engine making stock horsepower? Maybe they milled the head to make more compression? Maybe someone bored and stroked the cylinders and rods making power HP and torque? A bigger carb? Dual carbs? A change in valve timing. Ignition upgrades. More HP and torque means more heat. Don't expect a stock cooling system to keep up with engine performance modifications.

 

In my experience, if your pressurized cooling system boils over, its too hot.  If you can control it from boiling over you are likely ok. (within reason) Upping the rad cap pressure, changing the water/glycol ratio helps. Ensure your ignition timing is not too far advanced as this makes more heat. You can run "Wetter Water" type coolant products in the rad. It boils at a much higher temperature than water & glycol. You can get away with a lot of bad cooling system maintenance if you live in a flat area and travel at higher rates of speed. Lots of airflow can cover up a lot of sins in the cooling system.  If you live in mountainous terrain as I do, with a 119 HP flathead, 3 speed manual, the cooling system needs to be performing at its best. Long slow winding hills with lots of throttle means very reduced air flow and lots of heat. A traffic jam on a 100F day, things get ugly quick. No air flow.  For me I have learned to be  comfortable running my engine at 200F at times. I have to, its very hot here in the summer and we have steep hills around here. An engine runs more efficiently at 200F compared to 160F. There is better fuel combustion and less crap in in your oil when you run hotter.  There are less byproducts of combustion in your engine when it runs hotter. Cleaner oil means the bearings and piston rings last longer.  

 

I'm thinking about building a fan shroud for my '38 Plymouth. It can't keep up on hot days and steep hills. A previous owner removed the stock 201 ci engine. He put in a different rad and shoved it 2" forward it the nose cone area. A longer 25" engine was installed. 228ci. Great, more power! I rebuilt the engine 2 years ago. It's now a 237 ci engine. You guessed it...Now I am having trouble keeping it cool. I am hoping a shroud will increase the cooling system performance just enough to get me through the god days of summer. I will try. If not, I will have a find a larger, maybe 4 row radiator. Time will tell. 10. months of the year, no problem. July and August I have a problem. 

 

 

 

[Grimy]

On 4/27/2023 at 2:17 PM, Buick35 said:

I'm in Florida and not running any anti-freeze in my 35 Buick.What type of anti corrosion do most of you recommend and or water pump lubricant? Thanks.

I'm in the SF Bay Area where there is no worry of freezing (10 miles inland, there is).  For about 12 years now I've been using water plus Pencool (formerly Nalcool), a big-rig product purplish in color, that has anti-cavitation, water pump lube, and anti-corrosion properties.  Initial dosage rate is one ounce per quart of cooling system capacity.  Radiators remain sparkling clean.  I carry a gallon jug of replacement coolant with 4 oz Pencool and the balance distilled water.  Pencool comes in two variations:  Pencool 2000 is for no-antifreeze systems, and Pencool 3000 is for systems with any amount of antifreeze.  Pencool is best purchased from Amazon, as it is hard to find in brick-and-mortar locations, and I usually buy it in 64-oz jugs as most convenient for me.  About 10 years ago, I had email and telephone conversations with a Pen-Ray (parent company) chemist who is himself a car collector (Dodge Chargers) who understands the issues with unpressurized systems (all my fleet except the 4-psi-cap Jeepster).  I have no connection with Pencool other than as a highly-satisfied customer.

 

Like @Stude Light my 1910s and 1920s cars' cooling systems are actually batteries of a sort--dissimilar metals in solution!  So I use zinc anodes from a boat store as sacrificial metal, hanging from stainless wire inside the top tank of the radiators.  AND, for all cars, stockings in the radiator top tank through the upper neck to catch debris before it can clog the radiator.

[nat]

     I too think that hotter the better as long as you don't overheat or loose coolant.  Running too cold generates sludge.

     Pressurized or not, a cooling system filled when cold will purge some volume when it gets hot.

     As a rule, all water pump hoses are subjected to suction and should be wire bound or have a spring inside to prevent them from collapsing.  A common cause of overheating is the lower radiator hose collapsing under suction.  If the hose can be collapsed by hand, watch it when the engine is revved up.  Collapsing stops cool water from getting into the engine.

     In a pressurized system, the water leaving the engine is helping to push it through the radiator back into the engine.  If the system is non pressurized and the radiator isn't entirely clear and/or the suction hose is mushy, the water may leave the engine more freely than it gets sucked back into the engine and come out through the overflow.

[Stude Light]

10 minutes ago, nat said:

 I too think that hotter the better as long as you don't overheat or loose coolant.

Well, not necessarily. A pre-war open system was designed around a maximum coolant temperature of around 212 deg F. Running with something like Evans coolant, may not cause coolant loss but will run significantly hotter coolant temps. This may actually overheat valve guide or piston interfaces. If you're assumption was a water based system, I agree with you that running closer to the boiling point is better but you also want some added cooling capacity for those times in high temps/humidity or slow speed so you don't want this limit to be your normal operating state.

 

23 minutes ago, nat said:

In a pressurized system, the water leaving the engine is helping to push it through the radiator back into the engine. 

In a pressurized system you have to look at the entire cooling system as a "closed system". Having a pressurized system does not change the flow characteristics through the system. Assuming we are talking about a liquid, flowrate is flowrate and is not influenced by pressurized system vs non-pressurized. A water pump certainly does change flowrate, so perhaps that is what you were referring to (water pump vs convection system).

 

28 minutes ago, nat said:

If the system is non pressurized and the radiator isn't entirely clear and/or the suction hose is mushy, the water may leave the engine more freely than it gets sucked back into the engine and come out through the overflow.

The amount of coolant that gets sucked out of the radiator, pumped through the engine and then returned to the radiator cannot change as there is no variable storage unit in the system and you cannot compress liquid coolant. I don't disagree that you can restrict the flow (like with a collapsed hose) but you cannot suck more water out of one component than is returned. Generally coolant out the overflow is from too much expansion of the coolant or changing of state from liquid to vapor which greatly expands the volume of coolant in the system so "boiling over" has to go somewhere and it will force out liquid, vapor or both.

 

I'm not trying to be picky or argumentative, but being an engineer most of my life, I like to be accurate with technical descriptions. I think your suggestion on collapsed hoses is good.

[Grimy]

Re collapsed hoses:  Many if not all pre-war lower hoses were *originally* short sections of hose (perhaps 4 inches) with metal pipe between them, and often over the years the pipe rusted out or was removed for simplification in favor of a long stretch of either unreinforced or internal-coil-spring hose.  In my own cars, I return to the factory design, often using stainless or aluminized exhaust tubing with the sharp cut edges smoothed out.

 

Additionally, I've found in virtually every pre-war unpressurized car I've owned, that a 50% EG anti-freeze solution has a tendency to foam, even with a well-sealed water pump, and the foam prevents unrestricted passage in the top tank causing coolant to go out the overflow.  That's one more reason I prefer water + anti-corrosion additive, which substantially reduces the coolant-pushed-out effect.

[nat]

10 hours ago, Stude Light said:

The amount of coolant that gets sucked out of the radiator, pumped through the engine and then returned to the radiator cannot change as there is no variable storage unit in the system and you cannot compress liquid coolant.

        What can, (and does happen), is that a pump can move some engine water to the radiator which will overfill if the radiator is clogged or the suction hose is blocked. 

     Water is non compressible but expands under cavitation.

     

[Stude Light]

46 minutes ago, nat said:

        What can, (and does happen), is that a pump can move some engine water to the radiator which will overfill if the radiator is clogged or the suction hose is blocked. 

     Water is non compressible but expands under cavitation.

     

Nat,

What I really hate about the advent of social media is that it is a terrible place to have a meaningful discussion and debate and there is no way to judge someone’s demeanor in the conversation. I truly respect your opinions and say without trying to give offense that I disagree with the cavitation causing water to expand. Here is why: 

 

Cavitation is a localized event that occurs at the suction side of the impeller of the pump. Let’s just assume we are talking about water. It drops the pressure of the, now hot, water below normal atmospheric pressure whereas the water may boil at, say, 200 degrees. That vapor is now mixed with water at that moment. As soon as you reach the other side of the pump, the pressure is increased and the vapor turns back to liquid.

 

Cavitation results in noise, decreased pumping efficiency and will cause localized erosion of the pump components.

 

I’m not trying to be argumentative in the conversation. My primary point is having a restriction in the system will just slow the flow rate through the entire system. You cannot suck extra water out of the engine without creating any empty space elsewhere.
 

Having a restriction may certainly cause localized boiling or may cause air to be pulled past seals and when that happens you will get a significant change in volume of the coolant and expel stuff out the overflow, especially if there are other things in your coolant that are susceptible to foaming. That is often the result of what you see.

 

I know we can agree that restrictions are bad as are buildups of contaminants that decrease the heat transfer rate across components.

 

Respectfully

Scott

 

 

 

[nat]

On 3/1/2023 at 1:37 AM, Tonz said:

Please don't confuse topic with any info about pressurised pumped systems.

Cheers.

       I should first appologise for talking about pressurised systems and those with a pump.

       I respect your opinion and take no offense.  

       I'll PM you to continue this debate.

     Nat

[Tonz]

Thanks for the related replies about thermosyphon non pressurised systems. (It's hard keeping topics on the original subject)

Sounds like my Chrysler 50 is running temps as it should.

In my region winter does freeze engine blocks, I've seen a Velocette LE  motorcycle break off one of the opposing water cooled cylinders in on a frosty morning. So I'm going 50/50, green coloured coolant ... Which is correct for iron block engines.

As our winter is approaching I expect to see a 10° drop on the temp gauge. And the heat of the engine through the floor will be welcome.