I am considering switching from dot 3 to dot 5 brake fluid. My Chevelle is only driven between 500 & 1000 miles per year.
Does anyone know:
What problems if any will occur?
The correct way to flush out the old dot 3?
What happens if there is a little dot 3 left that mixes with the dot 5?

Sonny?
There has been a lot of discussion on this. Some folks think its a total waste, others love it (Bob Tiley & myself for 2). Go to the top of this page & hit search for DOT-5 you will find a bunch of opinions.

Bob just flushed his system with DOT 5 when he swapped. I took everything apart cleaned with brake cleaner, flushed lines with brake cleaner. Probably went overboard.
rick

Add me to the list of lovers. (Hmmm, that sounds kinda funny... Anyway...)All my Chevelles get it now. Just filled the new MC with it and bled it through all the lines. Never a problem and never again any eaten paint in my nicely detailed engine compartment, or the fenders. Supposedly more heat and moisture resistant and less corrosive to the brake system.

I tried it for the first time in my car. From what I understand, it is a much better fluid and will not absorb water so the brake system shouldn't end up with rusted cylinders and cruddy looking brown fluid.

Just open the bleeders and pump the fluid out of the MC. Then fill with DOT5 and bleed it through until it comes out clean at all 4 wheels. The stuff I used was purple so it is easy to tell when it is there.

You will need to almost empty the MC to keep the old fluid from mixing with the new in the MC. The stuff is too expensive to waste by mixing some and then having to bleed the mixed stull out. Unfortunately, that may introduce air in the system unless you are really careful. In any event, fully bleeding the system will remove any air introduced.

Only time will tell for sure, but it seems good so far and I want to put it into my daily driver.

Peter

I'm buttoning up the 12" discs on my 70 this week and there's a bottle of DOT5 waiting to get in the system. I chose the 5 because of Bob Tiley's good experiences with the stuff. I sure don't want my detailed frame/fenderwells to get eaten away by brake fluid.

Thanks to all who have responded so far. I am definately going to switch. My master cylinder leaked that awful dot 3 onto the booster and frame leaving me some painful touch up to do. I never want to deal with that again!

Thanks again.

Dot 5 can be had from your local Guard or reserve motor pool... (hint hint, any of you or friends in the guard or reserves??) I got a can (1 gallon of the purple stuff) of it free just by talking to the supply guy in there, though I am active duty Army too, but got it from the guard guys... We don't have a motor pool where I currently work. This will go into my totally new system in the next few days... Drive hard, brake well!!!

So you take the fluid from the government? So what you are saying is I need to buy your brake fluid? Not a good thing to do, much less admit too.........

Shame.........

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Redrum
68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28

Yes, we have it here at work too, because all Military Forklift vehicles we build must use DOT 5 silicone brake fluid. I guess all on road and off road military vehicles are required to run DOT 5? The purple stuff is nice because it's easy to tell when it comes out the bleeders but I used Carquest DOT 5 and it was not purple but clear/amber colored. I just rebled with some more DOT 5 to make sure I got all the old stuff out a few years ago and everything looked good. If you do not get all the old DOT 3 or 4 stuff out it will turn gummy when mixed with DOT 5 and that is something you don't want.
I have a pressure bleeder plate that clamps to the top of the master cylinder. I hook it up to 15psi of pressure from my compressor and the fluid squirts right out of the bleeders. Makes it real easy to flush a lot of fluid out of the lines. It's nothing more than a flat piece of steel plate with a rubber gasket and an air fitting over the master cylinder reservior. You just need to keep refilling the master cylinder before it gets too low.

Bono, based on the recommendations here I went with DOT5 after I repalced almost every major component of the brake system. ( DOH). Anyway, I paid a mechanic to power bleed ( purge) my system and cut all the drums ( for new Praise DynoBrake shoes). Cost was about $125 for all the labor. I notice nothing about braking feel or fade, some folks commented that 5 isn't as good. Bunk. Use it. My car is laid up for half the year too.

DOT5 is the only way to fly.

I am with redrum. Only I would not be so polite.