I did the unthinkable, added DOT3 To my master cylinder

[AECS]

I had not read as much as I should have and topped off my master cylinder with dot3. I have read about 20 threads now about which is better, and not to mix them. However I cant find what to do now. I am planning on just sucking out all the fluid from the reservoir, and filling with dot5 then bleeding till I get the new fluid to all the wheels?

 

[Al Harvey]

That's the best way that I know of to get it all out. I'd bleed a lil more after you first get new fluid at the wheels just to be sure.

 

[rosco]

Did it have any DOT 5 in it, when you topped it off? Was the bottom covered? If so, and you didn't use the truck/pump the brakes & such, suck out the Master Cylinder. If the bottom of it was covered, & you pumped a working brake system, chances are that you didn't draw any DOT5 into the system. At worst, remove & rebuild the Master Cylinder. The mixture is harmful to the rubber parts, making them swell.

 

[AECS]

It did have fluid, I only added about 1/4 inch to it, but have been driving it, so I will have to flush it and stand by to replace parts as they leak.... Thanks for all the responses.

 

[Scarecrow1]

Sound like you have the right idea and you caught it before it did any real damage ........ Well done Sir

 

[swiss]

You do have the option of flushing the system and changing out to DOT4. Lots of debate around this topic that you can read about but you do have options. If you are going to flush the system anyway at this point you have a choice. You can go DOT 5 which is more expensive or DOT4. Downside of DOT 4 is it will absorb moisture from the atmosphere, reduce the boiling point and thus effectiveness when breaking hard. DOT 4 has a 3-4 year life span. If you bleed heavily on a yearly or bi yearly basis you will be fine. Always use a new container of DOT4 and throw away any unused as it collects water sitting in your garage.

Something to investigate and think about.

 

[Skinny]

Uh...it may be just me but DOT 3 and 4 are glycol based and DOT 5 is silicone based. 3 and 4 are compatible with difference in boiling points, 5 is not compatible with 3 or 4. DOT 5.1 (a synthetic I believe) is a 5 alternate which can be mixed with 3 or 4 from what I understand but I have no personal use of 5.1 yet so I cannot speak on it's use.

If you didn't use the truck, suck it almost empty and fill it back up with 5. If you haven't changed brake fluid in 3-5 years, now would be a good time to get a one man bleed bottle and flush it. Be prepared to grab ankles when buying DOT5, I think I paid nearly $30 a quart last time at Napa.

 

[bigmike]

Stick with your plan of flushing out the entire system. Bleed it for a while so you are getting plenty of purple fluid thru all the wheel cylinders.

 

[doghead]

I would disconnect the output line from the master cylinder and again at the booster/air pack and flush each with 100% with new dot 5.

Then I would reconnect and bleed the whole system.

No point in pushing any contaminated(mixed) fluid though the whole system. This way you can most likely avoid contaminating the wheel cylinders.

 

[Tow4]

I had not read as much as I should have and topped off my master cylinder with dot3. I have read about 20 threads now about which is better, and not to mix them. However I cant find what to do now. I am planning on just sucking out all the fluid from the reservoir, and filling with dot5 then bleeding till I get the new fluid to all the wheels?

I did the same thing. Just suck it out, wipe the master cylinder out and then pour in the dot 5. If you didn't step on the brake pedal, there shouldn't be any in the rest of the system.

 

[hndrsonj]

If you didn't step on the brake pedal, there shouldn't be any in the rest of the system.

Post #4 says he was driving it.

 

[AECS]

Well here is the outcome. Yesterday I was pretty excited, as I called the guy I bought the truck from and he told me he had changed it over to dot3, cool I thought no problem.

Today I decided to double check him... bled of some fluid from right rear wheel cylinder, and mixed it with the DOT3 I had on hand, it separated right off... So I emptied out the master cylinder refilled with dot5 and got to bleeding. A QUART and a half later I had a clean clear solid stream of purple fluid coming out of each wheel cylinder and caliper.

So glad I double checked the guy...

I did not get any chunks or slime out, just nasty looking fluid that separated out when it sat. Looks like it was 50/50 dot 3 and 5. There are no leaks in the system and the brakes are working great. I am going to keep an eye on it and be ready to change wheel cylinders, calipers, master cylinder and hoses should the need arise. Thanks for all the help!

 

[dependable]

One time I mixed dot 3 and 5, not by mistake, but because I was on the road and needed brake fluid. My nearly new front calipers seized a few weeks later. Live and learn.

 

[AECS]

Yep, I am afraid I will be doing the same here real soon myself...