DOT 5? DOT3?

[m4A1]

Hi All,

Been lurking for a while but my first post. I've been trying to determine exactly what type of brake fluid I have on my CUCV. The tm says Dot 5 so I check my resovoir but the fluid does not match the color (suppose to be purple according to some sources). My CUCV came strait from the Gov so did all CUCV had dot5 or did some have dot3? And how do I determine what is in mine?

 

[jag7720]

I was just reading up on this and did a little search on the site. From what I understand the older version of DOT5 is yellow and the newer version is purple.... same stuff though

I also learned that you can buy the Mil-Spec fluid from http://www.sprucemtsurplus.com/ for $30/gal ... that is cheap. I am buying some today.

I also learned that you can test your fluid by pulling a little out and putting it in a jar... then add a little water to it and if it mixes... it is DOT3 ... if it DOES NOT MIX it is DOT5.

Being that your truck is fresh out of the service it prolly is DOT5 (the old yellow version)

All that being said... I am new to the CUCV arena and am still learning the vehicle

Jason

 

[maddawg308]

Question related to the DOT 5,

What are the advantages of using DOT 5 over DOT 3?

If a system is filled with DOT 3, and you wish to change to 5, what is the best procedure for doing this? How do you get ALL the old DOT 3 out of the lines before changing over?

 

[gimpyrobb]

Also, to add to the confusion, purple dot 5 turns clear/yellow over time. The best way to tell is to remove a sample and mix with water. Also, mixing dot3 and dot5 is reported to gunk up your brake system. I have not had it happed to me as I don't mix fluids, but I know Cattlet has had it happen to him.

 

[jag7720]

I had a conversation with the guy I bought my car from when I was converting my 1972 Datsun 510 from 5 back to 3. He converted it from 3 to 5. I wanted to convert it back because the brakes were soft and I didn't like the feel.

So, he said that when he went from 3 to 5 he had to clean EVERY part of the brake system with Isoproply to insure all of the old fluid was out cause you don't want to mix them. So, when going the other way you would have to do the same thing.

That meant that he had to take apart every line and cylinder and caliper and clean them. Major PITA.... is it worth it? Not to me, so I left it DOT5.

The other caveat is that the rubber seals in the system might not like the new DOT version you are putting in. They may ALL need to be changed.

Why do you want to convert to DOT3?

Jason

 

[tklm539]

check some of DDoyle's posts on this subject. I mixed 3 and 5 in my deuce and have seen no ill effects. I understand that the benifits of silicone are now gone, but I have not seen the problems people claim, and yes, I have been checking.

With that said, my brakes will go this weekend.

Tom

 

[ehuppert]

Been over ten years since i was a 63B, and fluid we were using back then was purple... Not sure when or where the yellow fluid came from... All of our vehicles had the DOT 5 (well, don't recall the jeeps or 880's having it!)

This is always a hot topic, along the same lines as synthetic vs. dino oil, converting r12 to r134, etc, etc...

The purpose behind dot 5 silicone fluid is that it isn't hydroscopic, doesn't absorb moisture. As for my personal vehicles, i've got some dot 5 in my stash, and don't use it. I'm a firm believer in flushing the system at least every other year so not overly concerned with moisture issues.

Personally, i would flush with dot 3 and be done with it... The fluids aren't supposed to have any sort of reaction when combined, so if most of the 5 is purged you should be okay...

After the 63b and some other assorted MOS's i became a "Loggie". I experienced first hand some of the stuff the government was sold in "thier best interests"!

Just my 2 cents!

Eric

 

[CCATLETT1984]

as long as you purge the system (do a complete flush with the new fluid.) you should be fine.

As gimpy noted above, I accidently put some dot 3 into my CUCV and had some horrible goo develop in the master cylinder. It took 2qts of dot 5 to get it all flushed out of the lines.

 

[Recovry4x4]

There's a TB in the TM section dealing with this!

 

[kentuckycucv]

I had a Dot 3 / Dot 5 stew in my master cylinder. I Love this site. I had no Idea about the DOT 5 fluid until I got here. Maybe the sheriff Dept, or the Oil change guys...or me put Dot 3 in the MC I dont know but I put it in a jar and it was a wierd emulsion.

Anyway the big question is what next???? Its already all mixed up... I removed the fluid out of the MC should I fill er up with DOT 3 or should I go buy the DOT 5

I can go either way at this point. I also have a picture of my MC goo in the photo album section.

 

[papercu]

fill er up with DOT 3 or should I go buy the DOT 5

It depends on how you drive your truck, if you drive it regularly DOT 3 is fine. The military changed over because at the time most vehicles did not see a lot of use, so water in the system was a problem. Wayne