Brake Fluid

You can use DOT 3,or 4. The DOT4 just has a higher boiling point which is good if you do extended periods of heavy braking, like coming down off a mountain.
The DOT5 is silicone and should not be mixed with the 3 & 4.
Jim

 

thanks!!! thats why i love this site.....super fast replies when ever you have a question about anything!!

 

If there is any way to flush system properly,I would do that,because that nasty old dot 3 eats paint ,INSTANTLY.But flushing it properly is a bear to do.

 

I have heard to use acetone or alcohol and then blow compressed air to dry the lines.

I think that would be ok if you disconnected the lines at the wheel and master cylinders then did the above then you need to dis-assemble the wheel and master cylinders and clean them and replace all the rubber parts.

Unless you have a lot of dirt , you would probably be ok just pumping fresh brake fluid through the system just run a pint or 2 of fluid through it till you get fresh fluid coming out at all 4 bleed screws on the wheel cylinders.

If the brake system is original and you dont know when it was last rebuilt its best to go through it and replace the flexible hoses and all the seals anyhow
I nearly found out the hard way that this needed to be done when a hose failed.

Regards, Robert

 

ok last night i flushed the entire system until clean fluid ran out of all the bleeders. There arent any leaks anywhere yet the pedal needs to be pumped to gain pressure in the pedal. The fluid level never got to low in the master where it could suck in air but its almost like the brakes need to be bleed again. What else could i look for? i plan on doing a complete over haul of the system during the winter but im trying to squeeze the last few days of driving out of it. Could the drums all just need an adjustment.....maybe the wheel cylinders have to far to push out? any ideas?

 

What type fluid did you decide to use? I have been kicking around changing to dot 5 since I'm replacing the front over to disc and dual mc. I would have to flush the back.

 

Sounds like you still have air in the system somewhere.
Terry

 

Agree,with Terry

As long as theres no Leaks of any kind, Theres AIR, start from furtherest back, ( Back pass side,) and keep bleeding each wheel cyclinder untill air is all out :tu
EXPERIENCED THIS SAME EXACT THING U ARE, WITH MY PLOW TRUCK LAST YR.

 

are the brakes spongy , or when you apply pedal pressure does the pedal slowly goes down to the floor ? if its the latter can also be the master cylinder has a worn bore or seal and is leaking fluid back into the reservoir

 

ok heres the update....went around and changed all the wheel cylinders, bleed the brakes all the way around, went for a test drive, whats happening is up above...is this it? Should i look into replacing the master cylinder?

 

I've heard really bad things about DOT5 brake fluid. It's silicone based, so people say that once you get it into your garage or on your car, you'll never be able to paint in there again. I guess it gets into the air and gets onto everything.

Second, it caues spongy brakes due to absorbing some air.

The upside is that it doesn't attack paint, but i think the downsides outweigh that benefit.

"DOT 5 is a silicone-based brake fluid. It is NOT compatible with any polyethylene glycol based fluids. Mixing DOT 5 with other types of brake fluids will start a chemical reaction that will cause solids to precipitate out of the mixture and inhibit proper brake system function.

Unlike polyethylene glycol based fluids, it is not hygroscopic, however this means that instead of being dissolved, any water in the system will eventually find its way to the lowest point in the brake line, corroding it, and potentially boiling and causing brake failure. Since it does not attract moisture, there is no way this will occur unless you are careless in cleaning out of the old fluid. Its major advantage over other forms of brake fluid is silicone will exhibit a more stable viscosity index in extreme temperatures, which is why the US Army likes silicone fluids. It is widely used in the antique automobile arena as well as it will not damage paint. From a lubrication standpoint, there is no appreciable difference."

"If you do decide to make this switch, be careful. You will have to completely flush you entire brake system of the DOT 3/4 before filling with DOT 5. Flushing with mineral spirits is enough to cause a complete system failure in a short time. In fact the introduction of any petroleum based products such as motor oil, power steering fluid, mineral oil (baby oil) even in small quantities will cause failure. The only way to properly flush this is with a brake cleaner that does not leave a residue.

In order to flush the system properly, every component must be removed and cleaned individually, then lubricated with the new DOT 5 and reassembled. You will also need to check with the manufacturer of your vehicle to see if this voids your warranty. This is the perfect time to see if any parts are worn and replace them accordingly. If done properly and no moisture is introduced into the system, you will not have to replace the internal components of your system again."

http://en.wikipedia.org/wiki/DOT_5

 

I'll be staying with dot 3, I had no idea there would be so many issues with dot 5, it sure sounded good in theory.

Thanks Chevynut for all that info

 

How many DOTs do you need?

I have DOT5 in my 57. I like the fact that it does not take the paint off. I like the fact that it is not hygroscopic (having the ability to absorb water) because I don't have to worry about taking the cap off the resevoir. The hygroscopic fluids when exposed to humid air draws moisture from the air silicone fluid will not.
I would not change to DOT5 unless it was a new system though, too difficult to clean the old water logged fluid out.
My clutch came with silicone as did my two other cars and my Harley so I only have one type of fluid around.
Jim

 

So many DOTs

Rick,
DOT3 and DOT4 can be mixed without any problem. If you do any heavy breaking you should up-grade to the DOT4 it has a higher boiling point therefore better peformance at the extremes.
Jim

 

Rick,
DOT3 and DOT4 can be mixed without any problem. If you do any heavy breaking you should up-grade to the DOT4 it has a higher boiling point therefore better peformance at the extremes.
Jim

Thanks,
I think I'll stick with the dot3 in the 57 since that is what I have in everything else I own.