Coolant Pressure

[jsw123]

I am using a standard automobile radiator on a 24/2 engine made by power anand. I am wondering what pressure it is best to run the coolant at.

[Tom]

Zero psi is best because even at no pressure many head gaskets leak.

[jsw123]

Do you use 100% coolant or 50% coolant.

Also, if it is at zero PSI, how do you keep the coolant from evaporating and thus needing to constantly add coolant?

[Tom]

I use no coolant, but since I'm in N.CA. it is not needed. And I use a open top 40 gal reservoir for evaporative cooling just like the origional Listers. I guess the answer to your question revolves around what type of cooling system you plan.

[oliver90owner]

Fairly simple to minimise evaporation.  Sealed radiator cap at zero pressure, overflow pipe into an expansion vessel and to the bottom of same.  Expansion losses are recouped by reverse syphoning, losses are minimised due to condensation in the expansion vessel (will be relatively cool). 

Antifreeze will not evaporate if it is glycol based.  You simply keep the expansion vessel filled with water (start with anti freeze mixture) to replace evaporative losses.  Your choice on coolant - water, if no risk of freezing, and as fancy a coolant/antifreeze mixture as you want to afford, depending on minimum anticipated temperature and a bit more for safety.  No mixed metals in most set-ups, so no more corrosion than fifty years ago when it was not a problem.

If you choose a methanol based antifreeze, I would suggest you change your mind.

Regards, RAB

[ronmar]

What Tom and RAB said...  The expansion tank, like that used on most any automobile will keep the radiator topped off all the time provided the pickup in the expansion tank is always below the surface of the coolant in the expansion tank.  The tank itself only has a small vent in the cap, so evap loss is very minimal.  I use a heatexchanger instead of a radiator, but have an expansion tank plummed into the highest point in the system.  It has been setting like this for 2 years now with no noticeable loss in level in the expansion tank from evap.  The level in the expansion tank of course rises when the engine runs due to thermal expansion...

The expansion tank I use is an off the shelf item at Napa.  Surplus center also had some similar ones that were real inexpensive.  I prefer the bottom feed type for this unpressurized application.  Here is a pic of how I have mine setup.