Packard Forum Index » Post-War (1946-54)

Overheating temp:

PRESSURIZED cooling systems use a pressure cap. The cap is measured in Pounds. IIRC each pound of cap rating is about 4 degrees.

EXAMPLE: The 55 packard cap is rated at 10 pounds. That means 40 degrees OVER boiling = 252 degrees. AFTER THAT the water begins to boil and will puke out of the overflow tube.

So overheating would be considered anyhting over 250 degrees.

There is some wiggle room on this tho. As Owen states it depends on whether the problem (radiator boiling) is chronic or the result of extreme conditions or unexpected under very cool ambient conditions.

For NONpressurized systems then anything over the 212 degree mark presents an overheating problem.


MOST IMPORTANT is to NOT trust a factory heat temp gauge. They are at best inferior quality across all manufacturers. When in doubt use a bourdon tube type gauge to test with.

EDIT: Under some high heat conditions a small amount of puking at the overflow tube may occur during very hot conditions. Small amounts off and on and here and there during the summer is not a problem. Unless it becomes chronic or excessive it is not a problem.

HOWEVER. Deteriorating cooling systems say 20 years and older can not always handle a pressure cap much over 6 or 7 pounds.

Need to check the cap rating and whether or not the cap meets the rating and has a good gasket.

Let's remember that these cooling systems were designed and tested by competent engineers to cope with expected conditions that might be encountered whereever they expected to sell cars. Since Packard historically exported cars to warm locales like Saudi Arabia, India, and Central and South America, we can assume they were designed to cope with these conditions.

Typically a cooling system is designed with a certain amount of overcapacity in anticipation of the fact that deterioration sets it almost immediately from things like build up of insulating corrosion products in the radiator tubes and hard water and other salt deposits within the engine block. The engineering philosophy was probably to design so that, with an average of deterioration, the cooling system would still be adequate for the expected service life of the car, perhaps something like 15 years.

Obviously there are a large range of experiences that can be encountered, depending on many factors, especially the frequency of change of antifreeze (remembering that the antifreeze properties of ethylene glyol doesn't significantly change over time, but the anticorrosive additives have a finite life), the hardness and mineral content of the water used, and just the general care given the car over the years.

I would be curious to see if the car overheats on just straight water. I knew a gal at work that filled her car up with straight anti-freeze and never could figure out why it overheated. Remember it's anti-freeze, not anti-heat. Anything more than 50/50 mix is too much unless you are in the Arctic circle. IMHO

Obviously the main reason for anti-freeze besides changing the freezing point of the coolant is to prevent prevent rust from forming.

Kev, there are two factors to consider. First, the greater the percentage of ethylene glycol, the poorer the heat transfer.

Second is the actual freezing point depression. Mixtures of ethylene glycol and water do not form a straight-line relationship to freezing point; at one specific dilution with water, the freezing point depression will be maximized and at either side of that, the freezing point will rise again. The 50/50 mix is close to the maximum freezing point depression that can be obtained. In other words a mix of 70% ethylene glycol will have a higher freezing point, not lower, than 50/50.

A similar situation exists with blends of Tin and Lead to make solder. As you vary the percentages, somewhere there is a minimum in the melting point, with higher melting points on either side. These are often called "eutectic" mixtures.

Thats good Information Dave. I never knew that. But I figured there was a point of diminishing returns.

Regardless of mix or scheduled maintenance that anyone wants to promote or use, the most important scheduled maintenance is to check the coolant with a mid range to good quality hydrometer EVERY YEAR!.

I do it every Thanksgiving. Shoot for -30 F. Will let it go if it's good to -15F or lower.

Hi Dave,
I would be interested to know the exact water to antifreeze mix that you make up for your "34" Taking into account that our winters are not far off yours in Jersey.
Terry

I use 50/50 by volume, and use distilled water. The distilled water is really only a good idea if your local water is fairly "hard" with lime, etc. as these salts in the water deplete the corrosion inhibitors almost as soon as you mix the ingredients.

Quote:

Dave, I believe that earlier you also recommended using the pre-mixed antifreeze and water mixtures that are now available because of the purity of the water used and convenience. Que no?

I plan on using the pre-mixed coolant when I refill the system in my 47 Clipper.

(o {I} o)