VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Brake Fluid Recommendation - Dot 3/Dot 5

I assume I'll be starting a debate, but I want to get as much information as I can to make a good decision. I'm restoring a 1941 Chevy Special Deluxe coupe. I have stainless steel brake lines, which I cleaned and flushed with alcohol and blew out with my air compressor. I cleaned all the junctions. I also installed a new master cylinder and all new wheel cylinders. I'm not sure what type of brake fluid to use. My car will be driven probably weekly during the spring and summer, occasionally during the fall, and not at all during the winter (it will be stored in my unheated garage). What brake fluid should I use? I hear that dot 3 is corrosive to paint, which I've spent (and will spend) lots on new paint and powdercoating. I hear that if your car sits a lot, the wheel cylinders can leak with dot 3. (If I used dot 3 and pumped the brakes weekly over the winter, would that keep them from leaking?) But, I hear that dot 5 can lead to spungy brakes and sometimes water accumulating in the system. As you can see, it's like I'm starting with a new system, so I'd like to do the best thing all around to have good brakes, but protect my paint, etc. What are your recommendations/experiences.

Thanks in advance to all who may respond.

Charlie

The 1936-50 Chevrolets with Huck brakes benefit from Dot 5. It can prevent the wheel cylinder pistons from siezing up...or at least delay the problem. I have Dot 5 in my '39 and the pedal is nice and firm, have had it in the system for over 25 years and never had a problem other than the frequent replacement of stop light switches. The fluid has been "refreshed" several times.
The Dot 3 attracts moisture and it mixes with the fluid. This lowers the boiling point of the fluid and promotes rust.
If Dot 5 picks up any moisture(its dosen't attract moisture as Dot 3 does)but the problem with the Dot 5 and moisture is that the water remains in a low spot. That is why the system should be bled out every few years.
The Dot 5 has been in my Corvair since 1990 and I have never done anything with it, keep putting it off.
With Dot 3 and Dot 4 you do have to be careful when bleeding the brakes as it will take the paint off the backing plates and wheels.
If your '41 was mine and has all new rubber parts (new like modern and not from 40 years ago) I would go with the Dot 5.

Thanks Gene! I appreciate the information.

I would have to agree on the dot 5 as I am just finishing my 41 town sedan and every line is new and stainless steel and all brake parts are new.

I have had DOT 5 in my '48 since '85 when the restoration was done. All my brake cylinders were new back then. My car has been driven over 25000 miles since '85 with no brake trouble. Two years ago I was packing the front wheel bearings and decided to pop the right front brake cylinder to check its condition. I found no corrosion at all and just few marks on the pistons where they were sliding back and forth. I put a new rubber cups back in but the originals looked fine and I think they would have worked OK. My car sits in my heated garage next to my furnace from Halloween to April.