Brake system overhaul dot3 or dot5?

[mikey]

Hello,

I have Peter Debella's brake kit for my 53 M38a1 which includes a new mc, wheel cylinders, rubber brake lines and brake pads.

Is there any reason why at this point I would NOT want to convert the jeep from dot3 to dot5?

If the conversion is recommended, then what is the best process to flush the system of dot3 now? I assume I'd want to flush it with the old lines and cylinders in place, but what would I use to flush out the dot3, denatured alcohol, methylated spirits, anything else? Keep in mind, only the copper lines will remain. All rubber lines, the master cylinder and wheel cylinders will be new.

Thanks

Mikey

 

[73m819]

If the system is new, I would go for dot 3 just because of the cost of dot 5, if for some reason the system has to be opened later, dot 3 is a lot easier to get and cheaper, we did a m62 new system with dot 3 for these reasons.

 

[o1951]

Dot 5 is great stuff.
Overkill in these applications, as systems were not designed for it. If the system has Dot 5, I would recommend carrying containers of it because, as others said, it is not as readily available.

I use Valvoline synthetic Dot 3&4. Other companies probably make it, but that is what auto parts stores here have. Here, in large containers, it does not cost much more than Dot 3.

Get all the benefits of Dot 4, and it is compatible with either regular Dot 3 or Dot 4, so I did not have to worry about getting all of the old fluid out, and in an emergency, I can use regular Dot 3 or 4..

 

[mikey]

Thanks for your input. I agree cheaper is a good thing, but the military did convert most vehicles, such as deuces, from DOT3 to DOT5, when DOT5 became available, because dot3 is hydroscopic and has the propensity to absorb water. I'm wondering what most people here have done, or are doing, or would do, with their M38's if they were rebuilding the entire brake system.

With a deuce, because of the weight of the truck and the fact that the single circuit brake system is it's Achilles heel, I would absolutely convert every one to dot5, but with the Jeep, I admit, the risk seems much lower. That being said, since I'm rebuilding the entire system, I'm just wondering what others would do. +1 for Dot3. Thank you!

Mikey

 

[mikey]

Dot 5 is great stuff.
Overkill in these applications, as systems were not designed for it. If the system has Dot 5, I would recommend carrying containers of it because, as others said, it is not as readily available.

I use Valvoline synthetic Dot 3&4. Other companies probably make it, but that is what auto parts stores here have. Here, in large containers, it does not cost much more than Dot 3.

Get all the benefits of Dot 4, and it is compatible with either regular Dot 3 or Dot 4, so I did not have to worry about getting all of the old fluid out, and in an emergency, I can use regular Dot 3 or 4..

That may be the perfect compromise. Thank you!

Mikey

 

[Fifty]

Dot 5 is the way to go. Flush the lines with air and make sure you bleed the system complete with the dot 5. The dot 5 will not have the problem with moisture as dot 3. Been using dot 5 for years, no problems. NAPA has it on the shelf in small bottles. The cost is not bad and I keep a bottle the tool box in my M38.

 

[o1951]

Dot 3-4 synthetic is not hydroscopic, that is why I use it.
I have seen internal corrosion on older well maintained Dot 3 systems, so I avoid regular Dot 3.

 

[mikey]

Dot 3-4 synthetic is not hydroscopic, that is why I use it.
I have seen internal corrosion on older well maintained Dot 3 systems, so I avoid regular Dot 3.

Right now the system has regular dot3. I did the water test. In your opinion, if I elect to go with synthetic, should I flush the regular dot3 or just add the synthetic?

Thanks

Mikey

 

[o1951]

Depends on which Dot you pick. If 5, got to get all the 3 out. If you choose synthetic 3&4, manufacturer says it mixes with regular 3 and regular 4, so I would just flush the best I could. I want all the 3 I can get out for corrosion issues and higher boiling point.

 

[mikey]

Depends on which Dot you pick. If 5, got to get all the 3 out. If you choose synthetic 3&4, manufacturer says it mixes with regular 3 and regular 4, so I would just flush the best I could. I want all the 3 I can get out for corrosion issues and higher boiling point.

Yeah, I know dot3 and dot5 are bad when mixed. I wasn't sure about regular dot3 with synthetic dot3 or dot4.

Thanks

Mikey

 

[Flyingvan911]

If you switch fluid, use alcohol to flush the old fluid out. Then put the new fluid in and bleed the system well to get all of the alcohol out.