VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Advice sought on engine coolant

I've had a history of hot running with my engine, finding out I had 40 head on a 53 block and rust in the cooling system, which is close to being remedied with a correct head and flushing rust. Would like input on coolant choices. Current plan is to use conventional pre-mix antifreeze with adding a rust inhibiter with possible (company claims) improved coolant performance called Water Weter. Thought about long-life antifreeze but seems to be formulated for specific newer vehicles, not to mention expensive, and my main concern is avoiding rust in the coolant system. Would appreciate thoughts comments on best practices with coolant/rust prevention experience now that the system is cleaned out and will have the correct head! Thanks much, Bob

Don't wast your money on pre-mix antifreeze. you are just paying for half a jug of water. I like the standard ethylene glycol (Green) stuff.

Check the prices between 50/50 and undiluted antifreeze. You'll find it's cheaper to buy the undiluted and do the mix yourself. I just checked pricing and 50/50 is selling from $10 to $15 per gallon where undiluted is just over $17 at O'Reilly and less at Walmart. Do the mix yourself and you'll get two gallons for just over the price of one 50/50 gallon.

I agree about the undiluted antifreeze but be sure you use distilled water and not tap water .

Thanks for cost perspective and use of distilled water. Any thoughts on Water Weter or other rust inhibitor additives?

With a good antifreeze and a clean system I would not use either. The antifreeze should already have enough rust inhibitor. Just keep in mind the inhibitors will not last forever so check the recommended change interval for the brand you use.

I use rust inhibitor/waterpump lube, but don't know about the other product.

I'm not a professional but I read years ago that the "antifreeze" properties of antifreeze coolant last forever. What gives up over time are the corrosion inhibitors. For years all I've done is add corrosion inhibitors every few years. New coolant shouldn't need any extra.

f you have well water or other rust promoting water choose the 55.50 combinaion.....you need n;y 1 1/2 Gals.

Tiny that would not be my choice as the inhibitors may lose their effectiveness but still remain in the system . My thought it's best to flush and refill.

There's a lot of things you can do if you so choose.

I've found that if you don't do some kind of filtering for your coolant system while you're trying to clean things up, you'll just end up with the same crap continuing to circulate.

They make a filtering device that can be installed between the top front coolant hose and the top of the radiator. I haven't used one but there seems to be value in it. You would need to drain the system (a little), clean the filter and refill until you're happy with everything.

If cooling is a standing issue with this vehicle (as it was with mine) you may want to up your radiator to a new aluminum. Not sure what vehicle we're talking about but if you get the right one, they're hard to tell from stock.

Also you can install an overflow tank and put your system under a bit of pressure. Manufacturers figured that out for better cooling and it's real easy to do. Admittedly I had to make my own tank to get a clear one, but now I can see the condition of my coolant and also the system garbage seems to deposit in my tank and not elsewhere. Well probably elsewhere too but at least I can clean the tank regularly.

I can send a picture of how I did mine if you like.

Hi Skidplate

Pressurizing the cooling system doesn't really make it cool better so to speak.
It only raises the boiling point of the coolant.
That DOES of course keep the coolant from boiling out of the system if you are running at or just over 212 degrees.
Which I guess could be called "cooling better". 🙂
It will NOT however make your engine run cooler.

An overflow tank isn't necessary though if you do choose to go the pressurized route.
This is only necessary to keep the radiator completely full of coolant.
And that of course is only necessary if you are using a "cross-flow" radiator.
Which is why it is now used universally.

Make sure you install a cap with seals and a valve that will allow the excess coolant to be drawn back into the engine. If not there will still be an airspace at the top of the radiator.

The first “coolant recovery” systems worked with a return valve. The end of discharge hose always had to be submerged in coolant so it would not pull air pack into the system.

Today the “overflow” tank is actually a pressurized part of the system.

Thanks to all for the very interesting discussion and suggestions. Very much appreciated. My 40 does have the overflow tank, although not transparent. Also using a light pressure radiator cap. The filter idea seems like it could be helpful in my situation, at least for some period of time. I suspect I will be in the periodic drain, flush and refill mode to keep the system as clean as possible. I hope having the correct head for my block will make a substantial improvement in cooling performance but keeping the cooling system as clear as possible of rust remains a task for sure.

Hi Rusty

None of our overflow systems/tanks are pressurized.
That includes a new 2024 Mazda CX 5.

Just curious, what did you see the pressurized tank on?

Interesting about your CX-5. The plastic tanks on all the BMW’s sedans I had since ‘99 were pressurized. And would fail from heat at about 100,000 miles! What a mess!

Other cars with pressurized tanks: ‘06 Mountaineer, ‘06 VW New Beetle, ‘17 BMW X3, ‘19 Flex, a couple of post 2000 Volvo’s.

I just looked under the hood of the Flex. There is no cap on the radiator. The cap on the overflow tank has 16 psi written on it. There is a vent to atmosphere in the cap.

The ‘95 Miata was coolant recovery only and not pressurized.

The overflow tank isn't pressurized but the engine and radiator is. The overflow tank allows the radiator to expel excess coolant when it gets hot and expands then pulls it back into the system when it cools back off.

And yes most aftermarket overflow tanks are not clear which is why I ended up making my own. Kinda odd that most are solid because I'm not sure how one would know if All Is Well when you can't see inside.

The overflow tank is far left. And the hoses you see that are disconnected are for the heater, not the tank.

Interesting!

Learned something new! 🙂

Thanks Rusty

A few comments on automotive coolants. I worked at the second largest automotive antifreeze/coolant manufacturer in automotive chemicals department. Much of our coolant business was the factory fill by the vehicle manufacturers including the largest auto and truck factories. They were based on real science and engineering.

Antifreeze/coolants contain additives to control corrosion and foaming. The additives have limited lifetimes that require addition or replacement. The interval is between 2 and 5 years depending on the operating conditions of the cooling system. The recommendations are based on test track and fleet testing results. Draining, flushing with clear water and refilling with fresh coolant is the best option. Mix the concentrate with distilled water available at grocery stores or other outlets.

Like most additives Water Weter is a waste of money. Very few have enough benefit to justify their cost. Too many actually cause more damage than any benefit.

It is not necessary to have a pressurized system to have an overflow system work. If the cooling system vents through a container containing a coolant level so air can be expelled but only liquid can be drawn in when the system cools. The circulating coolant will keep the system liquid full with a minimum of air that helps reduce coolant life.

. Hi Skidplate, Is the engine in a 1938 Buick with a 1941 Century manifold? .
. If one is to pressurize a cooling system not designed for pressure, it will blow the core apart and cause the heater to piddle on the passenger's feet. 4 pounds with an overflow tank is the best way to go.
. Lou .

Chipper, Very interesting post and yours plus the entire discussion motivated me to look further on the web for additive info and I came across the following: https://www.motortrend.com/how-to/0703-turp-cooling-system-additives/ and while the motor trend tests used a modern Honda vehicle the testing methodology and results were interesting, showing positive decreased cooling impacts of tested products on temperatures with and without antifreeze. On the cost side, one bottle of Water Wetter cost $14 at Auto Zone so not a terrible expense. Although I am as much concerned with the best approach to prevent corrosion as I am to reduce running temps as I hope my new head will solve the problem. Anyways, the Motor Trend test makes for interesting reading. But I hear you regarding possible adverse impacts over the longer. Last thing I want is to do harm.

First thing people need to understand is that coolant temperature is only an indicator of coolant efficiency. Let me try to help a reader understand that statement. Approximately 1/3 of the heat generated by burning the air/fuel mixture goes into propelling the vehicle down the road. Another 1/3 is transferred to the air circulating around the engine, through the exhausted gasses and by radiation from the hotter engine to surrounding air, metal or other solids. The final 1/3 is removed by the cooling system by transferring heat from the engine metal to a liquid coolant and then by the radiator to the air. If a coolant does not transfer as much heat from the engine metal to the coolant the coolant temperature may not rise as much. That results in the engine metal becoming hotter and much of that heat not transferred by the coolant going out the exhaust or directly to the air. It is hotter metal that you may not want and the coolant temperature does not indicate that.

I worked at a major supplier of antifreeze coolant products. We instrumented several Mazda rotary engines with temperature measuring thermocouples located close to the combustion section of those engines. The rotary engines were selected as they have separate sections of the engine for intake, combustion, power and exhaust. In piston engine engines the incoming fuel/air mixture alternately cools the cylinder and the combustion heats it. That makes quantifying the actual differences in coolants more difficult to accurately determine in piston engines. That research clearly demonstrated the differences in heat transfer or coolant efficiency for water and other coolants. Some products that resulted in lower coolant temperatures also had much higher engine metal temperatures.

My two cents worth: in the grand scheme of things, coolant and lubricant are low cost elements in what is generally a costly hobby. I buy pre-mix coolant (the green stuff) for my old cars. I don't stockpile it cause it has a shelf life. I change the coolant every 24 months, max. I flush the system at that time and open up every opening I can (reasonably) and run water till I'm satisfied. I shoot my engine with an IR thermometer in various locations under varying ambient conditions cking against my dash gauge. I do this so I'll know what to expect going down the road. I have used 3-4 lb caps just to gain an edge on boiling. I use a clear plastic recovery bottle. I don't use water wetter of other additives cause I figure if I need that, I've got some other problem and I don't trust them anyway. I tighten my hose clamps frequently and even have doubled them on some connections. I like to drive my car. I like to take trips with confidence. I don't like break-downs. This may not help but I feel better.

Hey Lou, sorry for the late reply. It's a 37 Special with the 41 248 dual intake and exhaust. I replaced the original radiator with a new aluminum version. The original was fine but I didn't want to chance a road trip with an 80 some year old weakest link. And if my memory serves me, it IS about a 4 lb cap. I pulled and checked and looked over the heater core and it was very clean and actually seemingly pretty robust. Never say never but it seems fine so far. This is my second overflow system to be installed. The first was on my 53 M37. I had doubts then but it too has held just fine.

I received a suggestion to run antifreeze water mixture of 70/30 to boost anti-corrosion elements in the cooling system rather than consider an additive for that purpose. That mix would also lower freezing and raise boiling temps but that is not of concern to me here in Virginia as the 50/50 mix would serve just fine on that score. However, I noted Chipper's discussion that the focus should be on the metal temps of the engine, which I can check via IR. But I wonder whether using a 70/30 mix would be a concern for adequately cooling block/head metal surfaces versus the 50/50. Is that a trade-off from different mixtures and, if so, should that rule against tilting to 70/30 for improved corrosion control? For that matter, is the assumption that corrosion control would improve wrong? Thanks for you views. Bob