Inliners International Forums General Discussion Hi Performance DOT 5 Vs. DOT 3

I am planning on doing a COMPLETE brake overhaul. I am even converting to power brakes and even a new master cylinder. I heard that DOT 5 was the best to use as there is a hole in the MC and that it allows it to absorb water and rot out the brake lines. I also heard that DOT 5 gives a spongy pedal. Anyone have any PROS and CONS for me? I would really appreciate a feed back on which fluid to use since i am starting fresh. Thanks

Dear Jayson;

DOT (Dept. of Transportation)3 is the specification that was used for many years until disc brakes came to be in the late 60's.

Due to heat generated in these systems (disc)the DOT raised the standard.

The hole you mention is a vent for the master cylinder & necessary. Also; brake lines don't 'rot' as they are stainless steel and the rubber ones are a special material especially for hydraulic use(s) due to the movement of suspention/stearing parts.

If a brake pedal is 'spongey' there is probably air in the lines.

Good luck, John M......

DOT 5 is fine as long as all the rubber components in your brake system are new. It is a good bit more costly though. DOT 5 does not absorb water as does DOT 3. There should be little if any difference in pedal feel or performance between DOT 3 and DOT 5. Another plus with DOT 5 is that it will not eat paint.

Though my gut feeling answer says stick with DOT3, you can Google search brake fluid grades and see what you get.
try:
http://www.csaa.com/global/articledetail/0,1398,1004010302%257C2026,00.html

BTW: stock brakes lines are plated steel, not stainless; and if you wait long enough the rubber hoses rot too!

I am so undecided. I dont want to use a fluid that is going to rot out my brakes since i am replacing every single part. It is expensive and i dont want to have to do it again. Anyone else have any strong opions about DOT 5 or DOT 3. PLEASE PLEASE. Sorry to beg but i am planning this project for a few weeks from now and dont want to make the wrong decision. Thanks!

Ever notice the glowing red brakes at the race tracks?This has to break down the fluid so we change ours periodically,might be a good idea for all of us.Just a thought

Jason-- Neither of those fluids are going to rot out your brakes. Period. As long as you maintain your brake system by having it completely flushed once in a while, everything should be fine. Personally, I would go with DOT 3 or DOT 4. Just my opinion. John

Jason, my Bronco II (with front discs) uses DOT3 and it has given me 21 years and 300,000 miles of trouble free brakes (normal wear of course). I will be using DOT3 in my 38 Stude project with complete faith. Sam

When 10 years ago we rebuilt the brakes on my spouse's '52 Chevrolet 4-door, we used DOT5 fluid and have had no problems with the brakes. Whichever fluid one chooses to use, it is imperative not to mix fluid types. Do not replenish a DOT5 system with DOT3, or pour DOT5 into a system started with DOT3. Either fluid will work well enough; just don't mix them.

God's Peace to you.

d

DOT 5 fluid has 2 areas where it is different than DOT 3 or 4. DOT 5 doesn't absorb moisture and it won't strip paint if spilled on a finished surface. When heated from excessive brake use it does make the pedal lose some of its feel.

The hot rod and custom magazines all seem to make a big deal about using DOT 5 fluid and invariably they mention about how it won't hurt the paint if you dribble some during brake service. All the car builders I know use DOT 3 or 4 and are simply careful about filling or bleeding to the system so it doesn't get on painted finishes.

Your new system won't suffer any if you use the DOT 3 or 4 fluid. The only harm will come if you spill it all over your new paint.

Fill it, bleed it, drive it.

Mike

Thanks everyone! I have come to my decision and it will be DOT 3. Thanks for all the advice.