BimmerFest BMW Forum banner

I did it! A zero pressure cooling system.

99K views 356 replies 95 participants last post by  Anthony540 
#1 ·
Well, I decided that if I run a zero pressure cooling system, I may not have to do that next cooling system overhaul. No pressure, no exploding radiator.

So I ordered a case of Evans NPG+ waterless coolant. Not cheap at about $120, but if it saves an overhaul............... The case was 4 gallons. It took 12 liters (or about 2 3/4 gallons) to fill the system. That leaves over a gallon for top-ups, since you can't add water or any other kind of coolant with Evans.

I fully drained the system, radiator, lower hose, block drains, and ran the heater pump to get it out of there. I must have got it all because Bentley says it holds 12 liters and that is exactly what I got in it. So everything must have been out and there can't be any air trapped in there. After the NPG+ fill I changed the 2 bar cap for a 1.4 bar one.

With a boiling point of 375 degrees there should never be any pressure in the system now.
 
#11 ·
As coolant gets hot, it expands. Since the cooling system is sealed, this expansion causes an increase in pressure in the cooling system, which is normal and part of the design. When coolant is under pressure, the temperature where the liquid begins to boil is considerably higher. This pressure, coupled with the higher boiling point of ethylene glycol, allows the coolant to safely reach temperatures in excess of 250 degrees.

The radiator pressure cap is a simple device that will maintain pressure in the cooling system up to a certain point. If the pressure builds up higher than the set pressure point, there is a spring loaded valve, calibrated to the correct Pounds per Square Inch (psi), to release the pressure.
 
#10 ·
How can you say that this is a zero-pressure system, when you have a 1.4 bar pressure cap on it?

I can't see much advantage to lowering the pressure by 9 psi.
 
#16 ·
Hey Chief,

Whats the part number of the 1.4bar cap? sounds like a good way to go to protect the system...

As long as the evans coolant doesn't corrode the water jackets/pipes etc... would be a nice longterm fix to the PM of the cooling system...
For "normal" coolant, it's not (protect the system). Once the pressure increases past 1.4 bar (which you will have in a "normal" BMW), all your coolant will escape right there. You will have a "controlled" if you will, crack induced on top of your expansion tank.

Now, even if it corrodes, you won't have pressure in the system, which might allow you to patch up a pipe or a hose even with ducktape until you're home. Not so if it's high pressure.

but how is it possible that this stuff would be able to heat up w/o creating any pressure?
I believe the boiling point of that liquid is very very high. Much higher than the boiling point of the normal coolant

I took the car for a ride on the freeway today, about 80 miles round trip, AC on, air temp in the 90's. When I got home I immediately opened the hood and opened the radiator cap. A very small psst sound, might have been 2 or 3 lb. pressure. This would be from liquid expansion. The real pressure in a radiator is built up from the liquid exceeding its boiling point. This pressure then raises the boil point of the liquid. It works just like a pressure cooker, and like a pressure cooker, if you pop the cap when its hot....disaster. The liquid in my radiator never gets even close to its boiling point of 375+ degrees, so no real pressure. If I wanted to eliminate that 2 or 3 lbs, I can cut the spring or drill a small hole in the cap, either will have no effect on the function of the system. In any event, I went from 30 psi to 2 or 3 psi in the system, which should be a good thing.
I will have to read on this. What's the freezing point of this stuff? We have very frosty winters, but if this stuff can withstand -40°C I might be game.
 
#15 ·
I took the car for a ride on the freeway today, about 80 miles round trip, AC on, air temp in the 90's. When I got home I immediately opened the hood and opened the radiator cap. A very small psst sound, might have been 2 or 3 lb. pressure. This would be from liquid expansion. The real pressure in a radiator is built up from the liquid exceeding its boiling point. This pressure then raises the boil point of the liquid. It works just like a pressure cooker, and like a pressure cooker, if you pop the cap when its hot....disaster. The liquid in my radiator never gets even close to its boiling point of 375+ degrees, so no real pressure. If I wanted to eliminate that 2 or 3 lbs, I can cut the spring or drill a small hole in the cap, either will have no effect on the function of the system. In any event, I went from 30 psi to 2 or 3 psi in the system, which should be a good thing.
 
#20 ·
Why wouldn't it? The liquid is just a hot, it just won't boil.

I'm not going to run out and test it. It wouldn't come on anyway. The Climate Control system only goes up to 90 and it's over 90 here today.
 
#22 ·
No, you don't need to change the cap. I just had it laying around and decided to use it. But, it is critical that ALL of the old coolant be removed before putting the NPG+ in the system. Water or traditional antifreeze will contaminate the system.

Per Evans: WATER IS CONSIDERED TO BE AN IMPURITY, AND HARMFUL TO THE SYSTEM.
 
#23 ·
This stuff appears to be designed for big diesel trucks. These engines run at a much lower temperature tham the E39 V8. Ever notice the radiators covered over in the winter, so the driver doesn't freeze to death?

There may be a point there.

Keep us posted.
 
#25 ·
Nice, how often do you have to change the fluid?
 
#27 · (Edited)
Per Evans: at least 100,000 miles.

"What is an Evans Waterless Coolant? Evans Waterless Coolants are the ONLY 100% waterless automotive engine coolant available on the market. All Evans Waterless Coolants are a chemical blend that results in more efficient cooling due to a higher boiling point. The increased boiling point of the coolant eliminates the occurance of boil over, cavitation, and detonation. Not only do Evans Waterless Coolants not boil over,they do not freeze. At extreme cold temperatures the coolants contract and become extremely thick, not becoming solid and expanding like antifreeze containing water. Because Evans Waterless Coolants do not contain water electrolysis and corrosion are also eliminated. Every Evans Waterless Coolant requires the entire cooling system to be drained (radiator, engine block and heater core) and refilled 100% with one of the Evans Waterless Coolants. No need to add anything. Evans now has three different coolants to choose from depending on the application and use of your specific vehicle. Also available is a flush fluid for smaller engines without block drains."

"Evans NPG+ Waterless Coolant is the most popular of Evans Waterless Coolants, recommended coolant for all gasoline and diesel engines. NPG+ is a year round, lifetime coolant. No other cooling system modifications are required for stock vehicles to run NPG+. Simply drain the entire system and fill. NPG+is safe for stored vehicles and vehicles operated in extreme cold conditions. Motorcycles and small engines are suggested to use Prep Fluid as a flush prior to installing NPG+. NPG+ meets or exceeds both the ASTM D 1384 corrosion test and the ASTM D 3306-94 specifications."
 
#26 ·
I find this very interesting. The traditional coolant has about 50% water, so naturally when you boil it to 90-105C, the water evaporates, increasing the pressure, pretty much like a pressure cooker like Chief said.

On the other hand, I wonder why car makers don't simply fill the cooling system with ATF as the coolant? It would be a perfect fluid to be used as coolant. I may be wrong.
 
#28 ·
don't oils retain heat? i think water is a better heat TRANSFER medium than oils. It's like the difference between aluminum radiators and copper/steel ones. aluminum costs more, but it's ability to dissipate heat is much better, so a smaller radiator is needed.
 
#34 ·
aluminum costs more, but it's ability to dissipate heat is much better, so a smaller radiator is needed.
I think you might have that backwards. And don't forget that copper is heavier. Many of the '02 guys convert to copper tripple cored radiators for better efficiency over the under-performing stock units.
 
#29 · (Edited)
Of all substances known, water has the highest latent heat capacity. But it has many other characteristics which create problems when used as a coolant. Low boil point, freezes readily, expands on freezing, corrosive, etc.

NPG+ boils above 375, it never freezes and it flows well down to -40, it is also non corrosive. It's just a bit expensive and can't be mixed with water or other coolants.
 
#30 ·
Of all substances known, water has the highest latent heat capacity.
Yes, and that is why we have this corrosive, evaporative, etc. fluid in our systems - it does a great job of taking heat out of the engine block and dissipating it through the radiator. So, what is the NPG+ heat capacity compared to water? How does your temperature gauge look compared to what it was with the regular coolant? You obviously did a lot of research before doing this, is there any data (preferably independent) about the engine operating temperature with the NPG+ compared to a regular coolant? This would be very interesting.
 
#33 ·
The temp gauge will read the same the liquid gets just as hot as regular coolant if i understand correctly the only difference is that it doesnt boil till 375* And since our normal temp doesnt get that high there will be no pressure in the system.
soooo, you can get the same results, the same performance, not having to worry about seal and gasket compatibility, readily available everywhere, and at 1/3-1/2 the cost. just to keep the system for generating pressure. even dealer supplied coolant seems like a better deal.
hmmm. tuff sell for me.
but good info... all that matters is that you like it and works for you.
 
#35 · (Edited)
You got it. No pressure, no exploding radiators, no spewing leaks. If a hose sprung a leak, no explosion, you could just wrap some duct tape on it as a temp fix, w/ no pressure things just last longer.
Cost? BMW coolant 2 gal required @ $20 each + 2 gal distilled water @$1 ea = $42 Total Cost.
Evans 3 gal at $32 =$96.
$54 diff. For me, worth a try, and if it saves me a cooling system overhaul.........

I especially like the fact that so many who don't seem to care what brand of coolant they have been using in their BMW, are now so concerned about Evans compatibility with seals and gaskets.
 
#41 ·
I must say that any idea to reduce the pressure of the cooling system sounds like a good idea to me. However, the engines are designed to run that hot and as a possible result, your emissions may possibly rise (as combustion may not be as complete).
Secondly BMW's anti-freeze contains corrosion inhibitors. Whilst I appreciate that inhibitors may not be required with a non-water system, I would need to confirm that before I tried it.
 
#43 ·
The operating temperature should remain relatively unchanged. If anything it might even be a just a tad higher, and then only under severe loads.

While many of Evans products are for race cars and other specialty uses, NPG+ was formulated as a year-round lifetime coolant for use in stock vehicles. EVANS NPG+ has a "Proprietary Corrosion Inhibitor Package".
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top