Engine consumes coolant only when reservoir has fluid

[mrvette]

full hot & cold?

Don't have the balls to open it hot. And i'd lose coolant opening hot.

I have no problem popping the radiator cap when my engine is at operating temperature...and the coolant doesn't spew. I don't have any water in my engine, just pure ethylene glycol. My 68, my 97 TBird DD, and my wife's 95 Seville all have pure ethylene glycol - the green stuff. The ethylene doesn't boil until 350 degrees F (?) so the coolant system is never pressurized. The first time I took my 68 out for a test drive, I didn't even have band clamps on some of the coolant hoses since the coolant system doesn't pressurize with pure ethylene glycol.

As far as i know the only no pressure coolant is the Evans stuff. I'd run it if it was cheap and non toxic. But the other thing that saves you in an overheat situtaion is the liquid to vapor phase transition "latent heat of vaporization" which sucks a lot of heat out of the hot spot in the engine so you probably want something that does transition. Nucleate boiling is the best situation so, pure water is still the best thing if only cooling efficiency is considered. Well maybe liquid sodium would be better but not practical.

I tried using 100 percent antifreeze once and it was a mistake. It did pressurize and the engine overheated once taken on a longer trip 1 hour +. Pure antifreeze has a very poor thermal conductivity. Most all fluids vaporize and have some partial pressure.

Roger on the CF site proposed what i have been thinking. There is a bigger "air" space when the reservoir is empty because it can't fully fill the system. That airspace acts as a bigger cushion so the pressure does not get as high. I have a very small leak somewhere that only leaks through under pressure close to cap rating.

I had a SBC leak once long time ago, proved to be a head gasket, leaked out near header #8 cyl....

that side has been a bitch on this engine through several cyl head combos...

I found to put a 1/2" copper plumbing TEE in the heater line, mate up a air jet into it, I used a a/c fitting so to monitor with my HVAC gauges....

that way I can pressure the system to cap ~16 lbs....and watch....hot or cold, same shit, same thing I do to check for HVAC leaks after a work over...fill with 125 lbs air, shut down, watch for leaks over 12 hours or so....so the rad cap blows off at ~16 lbs...same shit, watch gauge over time, allowing for air temp variations and engine heat/cooling....

make damn sure the rad is full when pressurizing ....

maybe listen around anyting making any sense with a open tube stethescope??

:crutches:

 

[68/70Vette]

full hot & cold?

Don't have the balls to open it hot. And i'd lose coolant opening hot.

As far as i know the only no pressure coolant is the Evans stuff. I'd run it if it was cheap and non toxic.
I tried using 100 percent antifreeze once and it was a mistake. It did pressurize and the engine overheated once taken on a longer trip 1 hour +. Pure antifreeze has a very poor thermal conductivity. Most all fluids vaporize and have some partial pressure.

The "Evans stuff" is polypropylene glycol. It's used instead of ethylene glycol because the polypropylene is not poisonous. Like ethylene, it has a nice sweet taste. It animals or children accidentally drink it, it'll do no harm. In fact it's used in food products. Read the small print about food contents, say for candy bars, and you see it listed. Evans's stuff is much more expensive than ethylene gylcol. A poster on CF said ethylene is illegal in Switzerland because of the toxicity and poly has to be used there.

Ethylene gylcol boils at 387 degrees F (197C). To use it and avoid pressurization, you must get rid of absolutely all water. If you have a water/glycol coolant solution, you'd have to drain and flush several times to get rid of all the water. I pop my radiator caps at operating temp and do get a little "psst" somtimes. Even though I know it won't spew, it still makes me nervous. My college roommate got scalded. He used a rag it open the cap on his car, and knowing it would spew, he crouched down in front of the car and just extended his hand up to grap the cap. Sure enough a geyser of boiling water and steam erupted. Unfortunately, the geyser hit the hood and deflected the water down onto the back of his head and shoulders.

Pure antifreeze does not have poor thermal conductivity IMO. Some heating/cooling systems use ethylene glycol as a heat transfer agent. Google ethylene glycol. All of the WWII liquid cooled aircraft engines used pure ethylene glycol as a coolant. It was commonly referred to as Prestone. It was first used in the Merlin.