Tech Tips

Home / How It Works / Tech Tips


At Evans Cooling, our technical team is always working on ways to help the many users of our waterless coolants. Here are some of our best technical tips.

Tech Tip: Avoid Overheating with Traditional Antifreeze? Good Luck.

You’re damned if you do and damned if you don’t, unless you’re using Evans Coolant. That’s a pretty drastic statement, but let me back it up.

When an engine is running hot with antifreeze in its cooling system, the operator can get into a situation where there are no good options to avoid overheating and potential engine damage. If the antifreeze temperature rises to its boiling (failure) point, there can often be no good way to recover the system equilibrium. Let’s say you’re driving a vintage or muscle car in town and the temperature gets out of hand. I think any motorhead knows the stress of that moment and the need to make the right decision soon.

If you pull over and turn the engine off, the pump stops moving coolant and the fluid in the engine will boil away; this is often referred to as afterboil. It can raise the pressure in the system above the rating of the cap because the steam cannot be released as quickly as it is building. This is a threat to hoses, hose connections, and pump seals in motorcycles. If the head has gotten especially hot on the exhaust valve side, it can warp, ruining the head gasket seal and making it necessary to remove the head to resurface it.

If you continue to run the engine to keep the pump going, you are continuing to create heat. The low RPM of idling may make less heat than revving it, but the pump speed is low enough that cooling is likewise reduced. Getting out onto an open road is not always an option.

We saw this situation at the first two rounds of the American Flat Track motorcycle series this spring. At the Daytona TT, one of the bikes on the podium had a big blue antifreeze puddle under it from afterboil; the air temperature was in the 50’s, the track speeds were high, and there was no dirt or mud in the radiator so the conditions were not those normally associated with overheating. At the next race in Georgia, they stopped the race to clean up after a crash and a number of machines using antifreeze boiled over. The announcer was saying how they should be using Evans Coolant as the riders were going in circles trying to get their bikes to cool down. While I don’t want to name the teams that were overheating, I will say that the winner of both events, Jared Mees on the factory Indian FTR750, never had a problem. You will be surprised, I’m sure, that we are a proud sponsor of his racing effort! You can watch the Flat Track racing live on or on NBC Sports starting in July. We’ll see you at the races!

Tech Tip – Evans Coolant Maintenance

Evans Coolant is essentially maintenance free. Now I know that the word “essentially” is a qualifier that can cover over a shady statement, so I’ll explain a bit more. There are really two aspects about 50/50 antifreeze that make regular maintenance necessary. The corrosion protecting additives settle out or are consumed over time. The other issue is that the 50/50 ratio will change over time reducing the coolant’s heat transfer property.

The additive issue is pretty well known, so I’ll leave that explanation as is. The glycol/water ratio is an aspect that kind of sneaks up on you. Topping up is needed due to fluid loss through boiling; if you need to top up, it’s a sign of coolant boiling – overheating.

The vapor formed within the cooling system starts out as an even mix of glycol and water, but the glycol component will easily condense back into the liquid because the boiling point of glycol is so high. This means that the vapor leaving the system is mainly water. (The water can’t condense in the surrounding fluid because the boiling point of antifreeze is higher than straight water.)

Over time, the ratio of the antifreeze mix will trend towards a heavier glycol concentration which lowers the heat transfer capacity of the fluid, making overheating a more common occurrence. This is why people will switch to a different antifreeze and conclude that it cools better – they have actually just gotten back to a 50/50 ratio.

Now, back to the maintenance needs of Evans Waterless Coolant. Our additives are different from those used in antifreeze; they are stable and remain in solution indefinitely. This means that there is nothing to go bad in our coolant and so it lasts the lifetime of the engine. I’ve used the same fluid in one of my motorcycles since 1994. The freeze point is -40F/C and it shrinks when frozen, so there is no freeze-burst danger, even in extreme cold conditions. If our coolant becomes contaminated with water or other foreign substances, then maintenance would be needed.

Tech Tip: Prepare Your Engine for Winter

As winter descends upon much of the powersports world, it’s easy to let your machine sit where you parked it last. Resist this unassisted hibernation! A little care now will save you so much trouble when spring returns; we all know the creeping guilt of neglect throughout the winter. The best solution is really to just keep riding year ‘round, but that’s not always possible. (Snow warriors, see below!)

Drain the gas from the carburetors if your machine isn’t fuel injected. Either fill the gas tank to the top or drain it completely to avoid water contamination due to temperature swings drawing humidity into the tank. If you can get ethanol-free gas or, even better, race gas, it will stay fresh longer; gas additives can help too. If your bike stands tall on the kickstand, put a block under the footpeg on the other side in case a slow tire leak threatens to tip the bike over in January.

Whether you are putting the fun away for winter or not, change your coolant over to a waterless coolant. Evans Coolant is stable and doesn’t go bad with time or use and there is never a danger of freeze-burst damage, so it’s the best solution for long term storage. If you’re lucky enough to be able to keep riding year ‘round, Evans Coolant will keep the engine metal temperatures under control regardless of conditions.

Last winter was a bit thin for many of our snowmobile riders and we’re excited for a generous winter this time around! Pull your sled out from under the junk that mysteriously accumulated over the summer and get it prepped to rip! You’ve got some time still, so get in there and put the most durable coolant available in your machine! Evans Coolant will stretch the riding season by allowing you to ride even if there isn’t the most perfect snow cover. A bare frozen lake or run down a plowed road for gas won’t overheat your engine if you’ve got a coolant that can handle it.Go to for some conversion tips.

Tech Tip: Coolant VS Metal Temperature

I recently saw on a forum someone asking how it can be possible to see a higher coolant temperature at the same time as our coolant is keeping the engine cooler. It’s not as crazy as it sounds!

First, let’s not confuse coolant temperature with metal temperature. People tend to focus on coolant temperature for two very good reasons, it’s visible on the gauge and engine overheating starts with overheating
the coolant. If you’re on the edge of overheating your coolant (220-230F), another 10 degrees will push it over the edge. The metal components, however, don’t care about a 10-degree rise.

The metal components can become overheated once antifreeze boils to vapour inside the engine. Local boiling around the exhaust valves will empty the cooling jacket thereof liquid antifreeze allowing the metal temperature
to spike by hundreds of degrees.

The temperature of our coolant can be higher at the gauge (we’re talking 10 degrees or less – not much) while keeping the metal temperatures at all locations under control. See? The science does make sense once you
understand what’s going on internally!

Tech Tip:  Multiple Pass Radiators

There’s the belief among some that the engine coolant can go through the radiator too fast and not have enough time to dissipate its heat or that it’s passing through the engine too fast to pick the heat up. This belief probably originated via the observation that removing the thermostat can cause the engine to boil over faster. Adding a baffle into the thermostat housing to restrict coolant flow will then make boiling over less prominent. (The reality here is that a flow restriction at the coolant’s exit from the engine will raise the pressure within the engine which raises the boiling point of the fluid inside the engine cooling jacket.)

Another method of slowing the coolant flow that people use is a multiple pass radiator. They see it as a dual benefit of slowing the flow and providing the additional cooling of more radiator surface. It does decrease the radiator outlet temperature, but the temperature within the engine will actually go up because the fluid spends more time there as well.

Regardless of the fluid used, it is always easier to transfer heat between liquid and metal than it is between metal and air. The system’s heat transfer limit is at the radiator. The radiator is more efficient with a greater temperature difference between the metal and the air. If the air temperature is 90 and the radiator temperature is 95, not much heat will transfer compared to an air temperature of 90 and a radiator temperature of 250. (I’m using extreme temp numbers here just to make the point.) This means that the cooler end of a multiple pass radiator is less efficient than the hotter end.

A cooling system works best when there is a fast coolant flow and the radiator temperature remains high because it can shed heat to the atmosphere better. Water-based antifreeze puts a limit on the coolant flow rate because the pump can only turn so fast before it cavitates. Basically, the low pressure side of the pump has a lower boiling point and the fluid will vaporize; the pump can’t move a vapor.

Evans Coolant solves the boiling point problem allowing aggressive pump speeds and eliminating the need for engine coolant exit restrictors.

Tech Tip: Hot Weather

It’s above 90°F the A/C is on, temp gauge has moved from normal to almost too hot what can be done? Most cooling systems today have a heater core built in for defrosting the windshield, cold weather heat or defogging in rainy weather.  Most people do not know that the heater circuit is on all the time in most applications.  Hot coolant is circulating through the heater core under the dash, this coolant does not go through the radiator to dissipate heat and help cool the engine.  The heater circuit is a radiator bypass loop, some system have a control valve that shuts off the coolant flow when heat is not condition to help lower the temperature why not be more comfortable and let the radiator do it’s job. To remedy this problem a simple manual valve can be installed in the heater feed line or a 1/4″ restriction can be fabricated and put in the hose.   Before doing this make sure the hose you select only feeds the heater core.  By shutting off or restricting this circuit it redirects the coolant flow to the radiator where the operating temperature can be decreased by 10 to 20 degrees.

Tech Tip: Decreasing System Pressure

Automotive cooling systems use “system pressure” to affect cooling functions. The action of the pump pushing coolant through the engine against restriction creates pressure.
This pressure varies with engine rpm when a crank shaft-driven pump is used; An electric pump maintains a constant pressure or varies the pressure related to engine temperature. System pressure can be as high as 40psi or more at the engine outlet/cylinder heads or as low as 5psi at the pump inlet during idle. A pressure drop, through the radiator core, accompanies the drop in temperature of the coolant

System pressure is affected by:

  • Engine design
  • Radiator configuration
  • Waterless coolants provide sufficient heat transfer, boil at a higher temperature, and are non-corrosive.
  • Hose size
  • Pump output

The only way to change this pressure is to increase/decrease pump flow or add or remove restriction from the system.

The water component of coolant boiling, in the hottest areas of the engine, creates expansive vapor, which further pressurises the system. “Cap pressure” refers to the amount of liquid and vapor pressure held in the system at the cap location. This is the only pressure that is obvious to everyone, it’s stated on the radiator cap. Depending on the location of the cap it can be as low as 4psi or as high as 35psi.

The boiling point of water, normally 212° F, is raised 1° F for every 3 psi. of additional pressure. A typical 15 psi. cap, will hold the water in the system up to about 257 degrees F. This does not mean there is no boiling in the engine up to this temperature, but it is the point, up to which the cap will contain the expansive nature of the vapor.

When using Evans Coolant in the engine cooling system these pressures can be decreased to maximize the system’s flow and temperature control capabilities. These changes are application specific and should be discussed before proceeding. Please contact Evans Tech Support at 1-888-990-2665 or

Tech Tip: Coolant Pump Drive Ratio

Do you know your coolant pump drive ratio? You can find it by dividing the diameter of your crankshaft pulley by the diameter of the water pump pulley.

For example:
8” crank /6” pump = 1.333, or 33% overdrive for the pump. 4000 engine RPM would be about 5300 RPM at the pump.
A figure less than 1.0 would indicate an underdriven pump.

For example:
6” crank /7”pump = .85, or 15% underdrive. 4000 engine RPM would be about 3400 at the pump.

Tech Tip: Thermostat

The thermostat in an engine cooling system has two purposes;  The first is temperature control and the second is restriction.  Thermostats are typically located in one of two places, the upper hose or the lower hose.  Upper hose locations control the coolant leaving the engine, typically a higher temperature is used,  and more restriction.   Lower hose location controls incoming coolant to the engine; The temperature and restriction is typically less than the upper hose location due to heat absorption through the engine.   Temperature control is determined by the OEM or the DIYer, per the application they are building.

Today’s OEM engines use many thermostat designs and the aftermarket has different designs for most applications (high flow, bypassing, fail safe, balance sleeve).   Removal of the thermostat is possible on some applications BUT NOT ALL!  Evans High Performance Coolant can take advantage of the different design thermostats or removal of the thermostat when possible,  due to a higher boiling point than water or 50/50.  Carbureted engines can benefit from lower thermostat setting, but computer-controlled fuel injection typically requires temperature control in a specific range.   For more information on your application please contact Evans Cooling Systems.

Generally, overdriving the pump will give better cooling system performance in a street car. (OEM ratios are often 25% overdrive or greater) A street/strip, road racing or off-road application which sees sustained high RPM, should underdrive the pump.

Coolant pump performance is affected by driven speed, also by radiator type, and by restrictions such as thermostat type and hose size.