Brake system & proper fluid
Road Warrior
Joined: Aug 2008
Posts: 1,306
Likes: 865
From: Sheboygan, WI
good call. You can put dot5 in a system that would take dot3 or 4 as long as you flush all of the old fluid out and don't mix, but if you put dot3 or dot4 in a dot 5 system, it can deteriorate the seals. I'd run dot5 and be on the safe side, plus dot5 won't ruin your paint if it somehow gets on it!
Elite HDF Member
Joined: Dec 2009
Posts: 4,598
Likes: 14
From: navarre ohio
dot 3 and 4 are mineral oil,they absorb water and boil when brakes get hot.4 has a higher boil point then 3.dot 5 is silicone it doesn't absorb water.nothing different in systems,you can use any of the three but you cant mix them..it turns to Jello and plugs everything up..the labels on the parts are just to try to idiot proof everything.makes it more confusing on custom work
Road Warrior
Joined: Aug 2008
Posts: 1,306
Likes: 865
From: Sheboygan, WI
I would disagree with this. I have personally seen seals fail in brand new parts because dot3 fluid was put in a dot5 system. The seals used in a part for a dot 5 system aren't required to be compatible with mineral oil. I'm not saying that they all aren't, but they don't need to be, so it's up to the mfgr as to what they put in there. They may be the same, but they may not. Either way, if you put dot 3 in and have parts that call for dot 5 only, you take the risk, and if they aren't compatible with mineral oil, you will lose function of your brakes. Again, I am not disagreeing that most of they time you may be right, but I am saying that I have seen the results of the opposite.
Tourer
Joined: Apr 2010
Posts: 293
Likes: 7
The difference is just in the make up of the fluids. The material of the o-rings is the same for both systems. You just don't want to mix them. I run a Wagner-Lockheed master with the banana clip rear and use DOT 5. Denatured alcohol is a good source to clean brake system fluid FYI.
That is entirely wrong.
Dot 5 systems must be sealed, and that is frequently done by means of a diaphragm.
You would be ill advised to run dot 5 in any "open" type reservoir.
Tourer
Joined: Apr 2010
Posts: 293
Likes: 7
dot 3 and 4 are mineral oil,they absorb water and boil when brakes get hot.4 has a higher boil point then 3.dot 5 is silicone it doesn't absorb water.nothing different in systems,you can use any of the three but you cant mix them..it turns to Jello and plugs everything up..the labels on the parts are just to try to idiot proof everything.makes it more confusing on custom work
It is the degraded mineral content of the "rubber" component in a dot 4 system that can react with dot 5 and form "yukky stuff".
No old worn system, no gunk.
This is all pretty well known by mechanics. Or should be, anyhow.
Tourer
Joined: Apr 2010
Posts: 293
Likes: 7
I would disagree with this. I have personally seen seals fail in brand new parts because dot3 fluid was put in a dot5 system. The seals used in a part for a dot 5 system aren't required to be compatible with mineral oil. I'm not saying that they all aren't, but they don't need to be, so it's up to the mfgr as to what they put in there. They may be the same, but they may not. Either way, if you put dot 3 in and have parts that call for dot 5 only, you take the risk, and if they aren't compatible with mineral oil, you will lose function of your brakes. Again, I am not disagreeing that most of they time you may be right, but I am saying that I have seen the results of the opposite.
Typically, dot 5 has no impact on (what I am going to call) dot 4 components, but dependent on the dot 5 "rubber"(they are not rubber) components, dot 4 can certainly degrade them prematurely, and even cause outright failure.
This is a thread about brakes, and some of the advice that has been given could easily cause death.
Scary.
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Road Captain
Joined: Oct 2010
Posts: 566
Likes: 3
From: rural ontario
My eyes must be playing up. This post actually makes sense, and is accurate.
Typically, dot 5 has no impact on (what I am going to call) dot 4 components, but dependent on the dot 5 "rubber"(they are not rubber) components, dot 4 can certainly degrade them prematurely, and even cause outright failure.
This is a thread about brakes, and some of the advice that has been given could easily cause death.
Scary.
Typically, dot 5 has no impact on (what I am going to call) dot 4 components, but dependent on the dot 5 "rubber"(they are not rubber) components, dot 4 can certainly degrade them prematurely, and even cause outright failure.
This is a thread about brakes, and some of the advice that has been given could easily cause death.
Scary.
+2
Cruiser
Joined: Jul 2010
Posts: 118
Likes: 0
From: USA
Hopefully everyone here does more research on any given ifo here, nobody's a expert.