Monday, February 27, 2017

Changing to Evans Waterless Coolant

Vintage cars have some unique cooling system issues that differentiate them from modern vehicles used for day-to-day transportation.  We may be able to address those issues with waterless coolant – a derivative of traditional cooling technology.

Conventional coolant boils between 212-240 degree, depending on formulation and system pressure.  Engines need to be warm to run efficiently, so they have thermostats to regulate running temperature.  With a thermostat that opens at 180 degrees there is only a narrow margin between the minimum running temperature and boil over.   That’s one reason most cars have radiator caps with springs that allow them to build up pressure like a pressure cooker at home. The pressure raises the boiling point, increasing the safety margin to an acceptable level.  At least that’s the idea.  It works well in newer cars but not so well for vintage iron.



Older engines often have parts that are weakened by age.  The 10-15psi of constant cooling system pressure puts a stress on those parts and at some point they will begin to fail.  The result is a messy cooling system leak.  Such leaks are quickly washed away on ordinary cars but cause hours of cleanup on collector vehicles.

Vintage engines often have buildup of deposits in the internal cooling system passages.  They create hot spots inside the engine where temperatures exceed the boiling point of even pressurized coolant.  That reduces cooling efficiency and can lead to overheating.

One cause of deposits is corrosion, which happens when the elements of the engine react with the coolant.  Surprisingly it is often the water in coolant that precipitates those reactions.  That’s why most car manufacturers call for regular coolant changes.

Another approach to combating corrosion is to eliminate the water altogether.  Evans waterless coolant is essentially a blend of glycols with no water added.  By itself Evans coolant has a boiling point of 375 degrees, far hotter than a car’s cooling system will ever get in normal running.   The higher boiling point means the cooling system will not build up as much pressure, and so will be less likely to leak.  If it does leak it will not spray under pressure as aggressively as it would in a conventional system.

There is a tradeoff to the higher boiling point coolant - efficiency.  Water is better at transferring heat than any glycol coolant, as long as it’s not boiling. That's the key. Engines with hotspots will almost always do better with Evans because boiling is reduced or eliminated.  When that is not a factor, vintage cars often have enough cooling system capacity to hold their usual running temperatures with the Evans coolant.  Other vehicles may run somewhat warmer due to the lesser efficiency, but that will not generally endanger the engines.

Water in its liquid state is indeed a superior heat transfer fluid but as soon as it turns to vapor that advantage is lost. Water vapor only has 4% of the heat transfer ability of liquid water.  Another way to think about that is that cooling water loses 96% of its efficiency when it starts to vaporize.  If that happens under heavy throttle things can go bad in a hurry.  Localized hotspots are the main source of transitory engine seizure.  The photo below shows a dramatic example of what happens when coolant boils away from a cylinder liner.  In a high end car this may be $50k of damage, perhaps substantially more.

Seized piston resulted from localized boiling around a rear cylinder liner
Use of Evans coolant reduces the likelihood of such a failure in most collector cars.  In that sense it's like using synthetic lubricant in the transmission where the higher breakdown temperature gives a huge additional margin of safety.  Evans provides the benefits of reduced corrosion and reduced pressure buildup/diminished likelihood of spraying leaks.

There are two considerations when using Evans coolant in vintage race applications, or when driving very hard. Water is obviously not flammable, but any straight glycol coolant (conventional antifreeze or Evans) is.  There is a potential fire hazard if hot glycol coolant is sprayed on exhaust manifolds in a crash.  The other concern in a crash is that glycol coolants are slipperier than either straight water or water/glycol mixes.  Some tracks ban it for that reason.  Spilled glycol can cause crashes.

Tests and calculations show that a typical water/glycol mixed conventional coolant will build a pressure of 16psi at 230F in a non running but hot engine.  The same system with 100% Evans would only hold a pressure of 2psi.  That is a substantial difference in "spray pressure" if a leak should occur.

In the non-racing vintage car community the benefits of waterless coolant generally outweigh the disadvantages.  The reduction of cooling system pressure extends life, and the removal of water reduces the likelihood of corroding hard-to-replace parts.  Finally the higher boiling point gives a great margin of safety for older cars that are driven in parades.

No coolant is good to drink, but conventional coolant is most assuredly deadly where Evans is much less toxic.  In the UK Evans is actually listed as non-toxic, but USA government rules dictate any fluid containing more than 10% ethylene glycol be labeled as toxic. If you do develop leaks that can be a vital point of difference to your pets.

When you make the decision to change to waterless coolant it’s important to install it correctly.  Traditional coolant is simply drained and refilled with little regard given to mixing.  When installing waterless coolant we need to remove all the old coolant – and all the water – to get the full benefit of the technology.  The best way to do that is with a dedicated flushing machine.  At Robison Service we use a machine from Mahle, a German manufacturer.  The flush machine pumps fluid into one end of the system and removes it from the other, ensuring a smooth transition with little intermixing.

Most of the time you will not need to make any changes in the system when switching to waterless coolant.  Some cars will do best with changes to the thermostat or electric fan settings.  A few cars with marginal cooling capacity will not have sufficient heat removal capacity; most of the time when that happens it points to a longstanding cooling system problem, not a problem with the new coolant.

Once you have made the switch it is important to only top the system with Evans coolant.  Topping with water will dilute the Evans benefits.  Evans sells coolant in gallon bottles to facilitate this.  They also sell their Prep Fluid (usable for top-off) in quart containers.  Remember systems with Evans tend to leak less because of the reduced pressure.

When planning the installation of Evans coolant remember that traditional antifreeze is mixed 50-50.  If you needed two gallons of regular coolant and two gallons of water you will need 4 gallons of Evans.   You will also need an initial supply of Evans Prep Fluid to clean out the system.  When changing a 4 gallon system to Evans you should expect to use up to 5 gallons of flush/prep coolant and 4 gallons for final fill. 

The line that carries old coolant out of the engine has a clear spot so you can tell when the new coolant begins to appear.  See the image below:



Once filled, you should check to be sure your water content is under 4%.  We use a refractometer for that purpose, as shown in the photos below:





Remember, whatever you do, old coolant should always be recycled, not poured into the sewer.




John Elder Robison

(c) 2016 John Elder Robison
John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent Lamborghini, BMW/MINI, Mercedes, Land Rover, Rolls-Royce and Bentley restoration and repair in Springfield, Massachusetts.  John is a longtime technical consultant to the car clubs, and he’s owned and restored many fine British and German motorcars.  Find him online at www.robisonservice.com or in the real world at 413-785-1665

Reading this article will make you smarter, especially when it comes to car stuff.  So it's good for you.  But don't take that too far - printing and eating it will probably make you sick.

3 comments:

gsmac said...

You state, "The higher boiling point means the cooling system will not build up pressure, and so will be less likely to leak."

It is my understanding that it is the expansion of the coolant as it heats up that causes the pressure, not the boiling - the coolant shouldn't ever boil.

The coolant expands, presses against the spring in the radiator cap valve, and is thus pressurized. Any expansion beyond the pressure rating of the valve causes the valve to allow coolant to escape to the reservoir. Once it cools and contracts, the valve allows coolant to be sucked back into the coolant system from the reservoir.

The coolant, in normal operation, should NEVER boil. So unless you are replacing the radiator cap with one without a spring valve inside it, how does the waterless coolant run with less (or no) pressure?

John Elder Robison said...

Gsmac, thanks for your comment.

The answer is a bit complex. Evans has a vintage Impala that has pressure and temp sensors throughout the system. They illustrate what happens in a cooling system in real life. With Evans coolant the expansion tank pressure stays steady at 2-5psi, regardless of load.

When the engine is driven the pressure at the outlet of the water pump (and also through the cylinder heads) varies from 10-40psi as a function (primarily) of RPM. There is a corresponding negative pressure at the pump inlet and while that happens the expansion tank pressure is holding pretty steady.

In a car with an isolated expansion tank you can expect to see pretty steady and low pressure, like that. If the same system is filled with water the pressure would be running close to the 15 psi cap limit. The difference is that the water builds more vapor pressure in its passage through the cylinder head because even at high flow and pressure some of it boils and that raises the system pressure.

If you put Evans coolant in a car where the radiator cap is on the radiator tank just downstream of the pump outlet you may still need a 15psi cap to hold back surges from the pump at high rpm. If your cap was on the suction side - like many cars with side tank radiators - you could use a 2-5 psi cap and be fine. The point is that system pressures are different at different spots.

In that Impala, if you fill with water and run hard with no radiator cap the system will overheat quickly under load because of uncontrolled boiling of coolant as it passes through the head. The same system with Evans coolant will run fine, cap off, but would vent a small amount of coolant due to the other pressurization factors. That is the difference.

Remember the areas around the combustion chamber are always well above the boiling point of water. The combustion chamber is over 1,000 degrees and when cars are run hard the exhaust manifolds are red hot. So the intervening coolant passages must be well above 212F. To cool those areas they rely on the speed of coolant passage, and the head pressure of the pump reducing the tendency to boil. That's true for any car, but more true for newer higher performance engines.

The Evans will expand like 50-50 conventional coolant but that is only one component of the pressure you see against the cap. In most cars the cap pressure is a function of basic expansion, accelerated expansion due to local boiling in the head, and surge pressure from the pump head.

Evans coolant eliminates one of those mechanisms of pressure buildup but the other two remain.

Thanks for your thoughts
John

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