• Steel Soldiers now has a few new forums, read more about it at: New Munitions Forums!

  • Microsoft MSN, Live, Hotmail, Outlook email users may not be receiving emails. We are working to resolve this issue. Please add support@steelsoldiers.com to your trusted contacts.

Why do I need DOT 5 brake fluid in my Deuce 1/2 ?

WillWagner

The Person You Were Warned About As A Child
Super Moderator
Steel Soldiers Supporter
8,516
2,697
113
Location
Monrovia, Ca.
^^ What he says. I needed to do a MC when I first got my truck and just converted it to DOT3. Never looked back, no brake isues ever, well except an air pak! But it left me with 3 in it and as far as I know, still going.

If I remember, it was used because DOT5 is silicone and will not absorb water, think fording , and doesn't bother paint. Like it matters, nothing hurts CARC! Dot 3 and 4 absorb water, 4 more than 3, so that can cause corrosion issues on the internals of the system. The rubber pieces parts are the same in any of the systems. One flavor or another won't hurt the rubber parts.....unless they are Chi-Com!

3 and 4 are WAY cheaper and can be found everywhere, 5, not so much.
 

WillWagner

The Person You Were Warned About As A Child
Super Moderator
Steel Soldiers Supporter
8,516
2,697
113
Location
Monrovia, Ca.
Here is a link to a post that explains the differences between the different fluids,

 

NDT

Well-known member
Steel Soldiers Supporter
10,406
6,418
113
Location
Camp Wood/LC, TX
If you drive your truck daily/weekly and do fluid flushes every few years, DOT 3 will serve you fine. If you don’t drive often and don’t flush, the brake hydraulic components will turn into a rusted mess. Silicone DOT 5 eliminates this problem. I redid my M38A1 Jeep with silicone fluid in 1981 and haven’t had any issues at all. Try that with DOT 3.
 

Mullaney

Well-known member
Steel Soldiers Supporter
Supporting Vendor
7,689
19,711
113
Location
Charlotte NC
Why ?

I'm sure this has been covered, abstractly, several times over the last 20 years, so if you know why, can you break it down for me, please ?

Because I'm not convinced .
.
Like @87cr250r said (just above) you can use any DOT brake fluid that you want to use. Naturally, DOT 3 is a lot less expensive. DOT 5 is "better" if you run through water. DOT 3 worked for YEARS

Just Don't mix them (DOT 3 and DOT 5)
 
Last edited:

VPed

Well-known member
Steel Soldiers Supporter
1,104
294
83
Location
Clint, TX
To be crystal clear, either type will work but 5 is incompatible with 3 or 4. This means your system needs to be cleaned of all old fluid before introducing different fluid.
 

Tow4

Well-known member
Steel Soldiers Supporter
2,096
646
113
Location
Orlando, FL
DOT 5 is what causes the rust problems. Since it does not absorb water, the water that gets into the system, settles to the bottom of wheel cylinders, master cylinder, etc. No amount of bleeding will remove it because the bleed screw is at the top of the wheel cylinder and water is heavier than brake fluid.

I bought my M35A2 from GL and picked it up at Ft. Jackson. It had DOT 5 in it. When I got home and went through the brakes, every wheel cylinder was corroded beyond repair and several were leaking. The metal lines were rusted out too so I replaced them also. I switch it over to DOT 3 after replacing the entire brake system.

The simple fact is, with DOT 3, the water is suspended in the fluid. When you flush the system and change the fluid periodically as you should, the contaminates (water) go out with the fluid. With DOT 5, the contaminates stay where they are, because they are not suspended in the fluid, they are sitting at the bottom.
 

oddshot

Active member
781
119
43
Location
Jasper, Georgia
To be crystal clear, either type will work but 5 is incompatible with 3 or 4. This means your system needs to be cleaned of all old fluid before introducing different fluid.
During my time as a mechanic, I have never done this. What liquid would be used to flush the DOT 5 out the system? Eeazy Peazy with a power bleeder.
 

Adrok

Active member
Steel Soldiers Supporter
90
181
33
Location
Rochester NY
I've flushed the system prior to disassembly and work.

Tapped and installed a bleeder in the bottom of the master cylinder. No problems yet. But once water is in the lines and down stream.....your going to have a challenge.

Post #5, 87cr250r suggests the addition of silicone based vacuum pump oil ( density HEAVIER than water ) as a method to purge water from the system.
I have not tried it (YET) but I like it.



The solvent flush I used on the system before work and repair.

 

m1010plowboy

Well-known member
Steel Soldiers Supporter
3,900
2,695
83
Location
Edmonton, Canada
We found a split, lower brake line on a deuce the PO converted from Dot 3 to Dot 5. Being in Canada with freeze thaw cycles, we likely create more internal condensation.....like the inside of a buried sea can...... and need to flush more. The Mattech figures the water can gather at a low spot and with enough....lack of PMS..... hang out at a low line. Ignoring PMS is the worst thing we can do to internal parts. Regular flushing is part of PMS Preventative Maintenance System

It's interesting because the fluid isn't 'traveling' through the system but somehow water appears to eventually gather at a party spot. Goose the deuce was juiced with Dot 3 in 2012 and here we are, April, 2024, still freezing.
 

87cr250r

Well-known member
1,265
1,986
113
Location
Rodeo, Ca
I just rebuilt the front calipers on my M1008. They had a waterline just below the midpoint, they were nearly half full of water. Luckily the bores are hard chromed and the pistons are stainless steel so corrosion was minimal. I put DOT 5 back in because I didn't really want to get into the rear brakes. There are certainly disadvantages to DOT 5.
 

marchplumber

Well-known member
Steel Soldiers Supporter
3,781
2,785
113
Location
Peoria, Illinois
I just rebuilt the front calipers on my M1008. They had a waterline just below the midpoint, they were nearly half full of water. Luckily the bores are hard chromed and the pistons are stainless steel so corrosion was minimal. I put DOT 5 back in because I didn't really want to get into the rear brakes. There are certainly disadvantages to DOT 5.
Thats good info.....thanks for sharing! Definitely a cause for possible concern.....i wonder where it "drew" that amount of water from? Any ideas?
 

msgjd

Well-known member
1,057
3,235
113
Location
upstate ny
while we're on this topic, how does one determine which DOT number is already in a truck? I don't notice any difference in color, smell, or texture , but that could be just my age .. No I'm not gonna taste it or put my ear to it ! :p

On one of my gov't-direct trucks without "silicone only" decal ,, I added DOT3 and it instantly separated. . It apparently was DOT5 :rolleyes:
 

ODAddict

Active member
Steel Soldiers Supporter
106
217
43
Location
Charlottesville, VA
Great info here, especially regards DOT 5.

As referenced above, the DOT 3 and 4 brake fluids are hygroscopic, i.e. they absorb moisture from the atmosphere. So, over time, water may intrude the brake system simply by removing the master cylinder cap to check the level. Or slightly worn boots or seals also may provide a path for moisture. either from the atmosphere or water splashing around on a rainy day. Or condensation formed in lines or areas that may have small voids.

As to DOT 5 (there apparently also is a DOT 5.1 available with which I am unfamiliar), the silicone-based fluid will not absorb moisture. But the problems of moisture intrusion over time remain. Difference now is where it ends up.

Now, where did I put my free lunch?
 
Last edited:

HDN

Well-known member
2,103
5,061
113
Location
Finger Lakes Region, NY
while we're on this topic, how does one determine which DOT number is already in a truck? I don't notice any difference in color, smell, or texture , but that could be just my age .. No I'm not gonna taste it or put my ear to it ! :p

On one of my gov't-direct trucks without "silicone only" decal ,, I added DOT3 and it instantly separated. . It apparently was DOT5 :rolleyes:
Take some fluid out of the truck and put it in a jar of water and mix it around. If stuff isn't mixing, it's DOT5 because silicone doesn't mix with water.
 
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website like our supporting vendors. Their ads help keep Steel Soldiers going. Please consider disabling your ad blockers for the site. Thanks!

I've Disabled AdBlock
No Thanks