What is correct Brake fluid for 1939 Chevy?

[Guest bb39Buick]

I just acquired a 1939 Chevy. It is very original (but not beautiful). The Brake master cylinder is empty. I do not want to put any of the new DOT fluids in because I am worried about it ruining the rubber seals. The 1939 Shop Manual says use GM Hydraulic Brake Fluid Super No. 9. Well I learned they do not even make it any more. So I searched for a Castor oil based brake fluid and they do not make that any more either. What do you owners of 30's and 40's use in your cars? Any suggestions would be very much appreciated. Bob

[Guest De Soto Frank]

DOT 3 or DOT 4 fluid should be fine.

These are both Glycol-Alcohol based brake fluids that have been in use for over fifty years.

DO NOT use DOT-5 silicone fluid unless you disassemble the entire system, replace all rubber, and clean all steel parts thoroughly with de-natured alcohol.

Be prepared to have to rebuild your Chevy's brake system anyhow; rubber parts do not last forever. A complete brake overhaul will run about $500 in parts, which is cheap compared to fixing the car / occupants after losing the brakes.

Better to check them out thoroughly before putting the car in service.

FYI - brake fluid absorbs moisture from the atmosphere, and most brake systems corrode from the inside-out; steel brake lines that look excellent on the outside can still have internal corrosion to the point of failure in a panic stop.

Good luck !

[Rusty_OToole]

The old time brake fluid was glycerine based not castor oil. Use the parts store Dot 3 it will be way better than what they had in 39.

Yes you will probably wind up replacing all the rubber parts anyway. They only last so long, and need to be replaced every 15 or 20 years.