Distilled water vs glycol based coolant

You don't say how hot it gets. The 84 and 85 QV have had a reputation of running hot since they were new cars. Ferrari eventually redefined overheating on them as boiling over. Also rodding out a radiator is a limited cure if indeed it is plugged or has scale.

That being said water alone does transfer more heat than water with antifreeze.

You are experiencing the reason the 328 got a complete redesign on the cooling system.

 

Don't. Water alone is not what you want to do. You don't want the water boiling and doing weird stuff in there - like being corrosive.

They make an additive to help you. It raises the boiling point of water, and has corrosion inhibition properties. It's Ethylene Glycol.

The only other thing you could try would be a surface tension reducer (purple ice, water wetter).

Did you make sure both fans were working?

Bigger radiator or ensuring yours isn't full of scale are also things to consider.

 

Ethylene glycol has a lower specific heat capacity then water. it's primary use is anti-freeze.

Water is the best in terms of heat transfer, however there are issues with surface tension and corrosion along with pressure and temperature.

 

I placed a lower temp radiator fan switch in my car and it helped. The coolant has a ways to travel from the engine to the radiator and back giving a delay in the fans coming on. Example say the engine coolant is 200 degrees it may only be 180 at the radiator. Also with a lower temp in the radiator allows more heat dissipation when it gets to engine. There is no down side to a lower temp switch as the thermostat, working properly, won't open until the coolant in the engine is up to temp.
-Barf

 

Lots of folks in the marine world use only water with a corrosion inhibiter added for precisely the reasons mentioned - water has a better heat transfer capability than water/antifreeze.

BUT YOU DO NEED A CORROSION INHIBITER AND IT NEEDS TO BE COMPATIBLE WITH ALUMINUM! There are a variety of products - Water Wetter is one (I have never used it and I'm not recommending it; I just know it is widely used) - that will provide the inhibiters necessary. But otherwise, give it a try, it MIGHT lower your temps a bit. It certainly won't hurt anything. Obviously, if you live in an area where the temps get down to/below freezing, no antifreeze would be a BAD plan.

There is a coolant - I can't recall the name - that Jay Leno supposedly uses in all his cars. The claims are a bit OTT but it might be worth researching...

 

Not sure if this is relevant but the Lotus Esprit has exactly the same cooling system layout as these cars and they overheat in traffic if the idle speed is set too low.
The too-low idle means the water stops circulating and doesnt go through the rad owing to the resistance in all the plumbing.
This is easy to detect, if the gauge creeps up when idling, and then when you increase the revs up to 1200 RPM it creeps back down again.

 

It's not just antifreeze, it's anti-boil. These additives do reduce the heat transfer compared with water, but hot spots, particularly around the exhaust valve, can lead to nuclei of micro boiling, which are quite damaging (a subject for a different discussion, perhaps). This is reduced by the increased pressure in the system from the cap, but further reduced by anti boil additives.

 

I have this stuff (the "high performance" version) in my 105 series Alfa Romeo racing car:

Evans Waterless Engine Coolants | Vintage Cool 180° | Classic Cool 180° | Prep Fluid | Power Cool 180° | Aero Cool 180° | Aero Prep Fluid

I love it. I had it for the first time/tested it the whole last racing season. No boiling, no bubble-forming/no "hotspots". Of course all your cooling system components need to be in correct working order, but this stuff keeps the overall temperature of my racer appr. 8 degrees (Celcius) lower. One should first "flush" with a special liquid that "binds" the last bits of old cooling fluids, then the actual cooling liquid.

I'll also will use this stuff on my 308, as soon as the sunny days are there and my car is back from the painter !

 

Yes, that's the "Jay Leno" stuff I couldn't remember..!

Re water/inhibiters - the inhibiters that the marine guys use contain the anti-boil/micro bubble stuff. This is vital for proper operation, as noted. If my boat/car did not live in winter/below freezing environments, I would not use antifreeze at all. OTOH, the 328 engine, with 50/50 water/antifreeze doesn't have any problem in bumper/bumper traffic with the AC running at 108F outside temp so, as RifleD pointed out, Ferrari made some major changes to the cooling capacity with the 328.

NOTE, I am NOT claiming that the 328 AC can actually cool the cabin in those conditions but running the AC does not adversely affect engine temps in those conditions.

 

This ^

Pure water will work very well as a coolant so long as the max temp of the system, or any specific location, does not exceed the nucleate / film boiling point of water.

Most every car engine will have spots where this temp is reached. Once film boiling occurs, that surface is essentially now mostly air-cooled, as the water is no longer in good contact --- there is a thin boundary layer of air. Air is a very poor fluid for heat transfer compared to water. This causes overheat problems locally on surfaces, and will do damage.

If you wish to use water only, you must be very careful and have a very thorough understanding of the system you are trying to cool. I would never recommend 100% water for any car (internal combustion) engine ---- it is way too marginal and too close to the edge.

As most point out, the main purpose of glycol (ethylene or propylene) is for protection against freezing. However, when added to water, the solution has a higher boiling point than pure water, so there is a benefit on the hot side as well. Although the heat transfer capacity is slightly reduced, this is far outweighed by the reduction of boiling occurrence.

Chemistry 101 --- When you add a solute to (most typical) liquids in the appropriate concentration, both boiling point elevation & freezing point depression are achieved. (i.e., the boiling temperature is higher and the freezing temperature is lower ---- than that of the pure liquid by itself).

Try this concept for yourself --- Boil a small pot of water on your stove, and as soon as it comes to a boil, dump in a handful of ordinary table salt ---- and observe what happens (you already know what it does in terms of preventing water from freezing)

 

I'd flush the radiator/ cooling system, use Fedi Bilstein high performance coolant but the 308 wants airflow like an old VW.

Install a two core wire from underneath the dash towards the fan switch with a small toggle switch say next or beneath the stereo. Flick the switch when idling in traffic, this will ensure the fans blows before high temp is reached not giving system chance to overheat, switch off again when escaping towards the open road.

Ciao