Converting from dot 3 to dot 4 fluid question

[400sforever]

i have installed new wheel cylinders, new hard lines, new rubber hoses and new master cylinder. Is there any reason I can't put dot 4 fluid in the system? From my understanding this fluid will not have rust issues?

 

[Charged440]

Should be no issues if everything is new.

 

[F4R/T]

I know crossing the streams isn’t good! I do know freight liner only uses it in the clutch slave on their trucks and 99% brake stuff I’ve seen is still DOT 3 . That being said every last component must be able to handle the DOT4 or you could have potential issues. I was also told it’s better for heat but I still wouldn’t switch.. your call good luck.

 

[Frank Mopar]

Google it up. Plenty of info about brake fluid compatibility.

 

[MoparLeo]

Just like any other fluid, changing it regularly is what makes the difference. DOT 3 is cheaper and if changed before the moisture content is past recommendations will not give any issues.
A brake fluid moisture content measuring tool can be got for less than $5.
. .https://www.ebay.com/itm/174815801213?epid=23021987623&hash=item28b3d56f7d:g:YXYAAOSwAs5g1iat

 

[4mulas]

Zero issue with using 3 and 4 interchangeably and even mixed. 4 just has a higher boiling point than three.

You can’t mix dot5 with 3 or 4. 5 is silicone based.

As for rust, moisture gets absorbed by both 3 and 4 so rust is still a possibility over long periods and high moisture. 5 does not absorb moisture, moisture just gets suspended in 5.

 

[PurpleBeeper]

What 4mulas said.....exactly what he said. No issues at all, but DOT4 is just high boiling DOT3. I "think" you're thinking of DOT5

 

[WileE]

What 4mulas said.....exactly what he said. No issues at all, but DOT4 is just high boiling DOT3. I "think" you're thinking of DOT5

I think you're thinking what I think he was thinking. What do you think ?

 

[493 Mike]

Whole lot of thinkin goin on here!
Mike

 

[ckessel]

Since brake fluid is hygroscopic, attracts moisture, the old stuff makes great weed killer. Sucks the moisture right out and its biodegradable.

 

[400sforever]

Thanks for all the replies! Maybe 5 is what I was thinking about? Sounds like a lot of you are using dot 3 and not worrying about it as long as it's changed out in time

 

[Don Frelier]

I've had dot 5 in my charger for over 20 years. I converted my truck 12 years ago.
No issues.
Dot 3 is awful stuff.

 

[400sforever]

I'm seeing a lot of dot 5.1 labeled fluid. .is that different than dot 5?

 

[YY1]

I converted to DOT 5 and while the pedal travels a bit farther, and slightly more pedal pressure is required, my master cylinder is still shiny black painted and I'm not worried about loosing paint on the firewall if the rear MC seal starts leaking as is common.

 

[400sforever]

Thanks for the replies. It looks like dot 5.1 is an updated version of dot 5. They say 5.1 can be mixed with 3 and 4. Who knew brake fluids were so complicated

 

[ckessel]

5 is silicone based and all by itself. Cannot be combo'd with the others. If you go 5, you need to flush out the system to remove old stuff. Take apart master, calipers etc to clean out residual with either alcohol or brake cleaner. Flush lines out the same. From there fill and bleed. 5 is not the same as 5.1. 5.1 can replace/upgrade 3 and 4.