Packard Forum Index » Pre-War (1899-1942)

I need to flush my coolant and while I have the various recommendations from 1939 manual, I was hoping folks could tell me what they've used and more importantly what I should avoid for my '39 Six. Thanks.

Regular conventional green 50/50 antifreeze.

Hello all, I would advise caution with using the modern anti freeze liquids in a Packard with a soldered radiator. Modern anti freeze compounds ( n.b. 250ml will kill the average adult human so don't drink it if you break down in the desert) are designed for aluminium radiator cores not soldered cores. I have removed all of the Glycol anti freeze compounds from my 38 old vehicles ( including older Rolls-Royce and Bentley vehicles due to this). My 1928 533 started to develop weeping at the core and I am certain that the use of the leeching antifreeze was a major cause. Following is some notes that I put together in 2015.
COOLANTS......IAM or OAM....Modern engines have anti-freeze/anti boil coolants which are basically a poisoned Chalice....they are good for modern cars with aluminium and plastic radiators but bad for old radiators with solder /copper/brass in the system. The problem is that the modern coolants react with the non-ferrous components and cause leaks and corrosion.
If you are prepared to pay $16,000 and replace your Phantom 11 radiator then you should not be reading this...but your Business Manager should.
As with most things, we the consumer have been duped to believe that modern anti freeze/ antiboil products are good for old cars.....bullshit...read the fine print.... Penrite put out a Coolant additive which I hope is satisfactory but have yet to see any Technical Reports on the product. I would recommend caution as most of the products are for post 1980 vehicles and will eat your 1901 to 1956 radiator over time. How long... well my 5th Series radiator has developed a few leaks over the past 5 years that I have been using modern coolants.
Ethelene Glycol anti freeze compounds work ..but you should replace probably every two years. I have also introduced all of my vehicles to Water Wetter as an anti corrosion and anti boil agent. It modifies the surfactant effect of the water molecule and allows greater heat transfer from water. The Engine runs much cooler when it can get rid of heat. .
Peter Toet, Packard Automobile Club of Australia - Technical Officer.