DOT 3 / Dot 4 brake fluid question?

**davered00ss** · 08-18-2007, 12:05 PM

I just installed slotted and cross drilled rotors with Hwak HPS pads. I want to change the fluid to DOT 4 without draining it out of the calipers.

The plan is to suck out the fluid from the resivor before I pump it into the calipers and fill with DOT 4. Can this be done, or should I stick with DOT 3?

**Wesman** · 08-18-2007, 06:14 PM

Just go with Valvoline SynPower Synthetic Brake Fluid. It meets both DOT 3 and DOT 4 specs, so its compatible with both. Just get as much of the old fluid out as you can, and top it off with the Valvoline.

This is it:

Hope that helps.

**jperkins812** · 08-18-2007, 07:20 PM

Originally Posted by Wesman

Just go with Valvoline SynPower Synthetic Brake Fluid. It meets both DOT 3 and DOT 4 specs, so its compatible with both. Just get as much of the old fluid out as you can, and top it off with the Valvoline.

This is it:

Hope that helps.

I would agree, it is the same stuff I use in my motorcycle without any problems.

**davered00ss** · 08-19-2007, 05:34 AM

I'll have to check that out. I did find out you can't mix DOT 3 with DOT 4, so I would have to flush the system. I may flush it with that.

**Wesman** · 08-19-2007, 08:32 AM

Originally Posted by davered00ss

I'll have to check that out. I did find out you can't mix DOT 3 with DOT 4, so I would have to flush the system. I may flush it with that.

Well you won't need to flush the system if you use the Valvoline, because its compatible with both.

Conventional DOT 3 isn't comptible with conventional DOT 4, but the Valvoline can mix with either, since it meets both specifications. Similar to the new "All Makes All Models" Antifreeze they have now, you can't mix green and orange, but the new stuff is compatible with both.

**hamburger68** · 08-19-2007, 01:21 PM

...but another important suggestion: break fluid attracts water, it ages. if it's older than two years, you should replace it.

**mrr23** · 08-19-2007, 03:01 PM

yes, brake fluid is hygroscopic, or attracts water. also, over the years, the brake fluid deteriorates the rubber brake hoses. just like any other fluid/oil, it needs to be changed because the viscosity breaks down. flushing the system is a great idea. this will firm up the brake pedal.

flushing the system is nothing more than replacing the old fluid with new. the master clyinder has a screen in it. what i do is start bleeding the system until the reservoir is just about empty. then fill it with whatever you are going to use and keep bleeding the entire system at each caliper until you see it change colors. i start with the left front, then right front, left rear, and finally the right rear.