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dot3, dot4, or dot cotton?

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-Savage-
World Chat Champion



Joined: 10 Jun 2005
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PostPosted: 18:32 - 25 Feb 2006    Post subject: dot3, dot4, or dot cotton? Reply with quote
ok, i hove some dot3 hydrolic fluid here, but my front brake reservoir says it needs dot4. whats the difference? and should i risk using dot3?
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 19:24 - 25 Feb 2006    Post subject: Reply with quote
Hi

Probably more info than you want to know, but:-

Quote:

DOT 3: This brake fluid has a glycol base with additives. It is clear to amber in color. It is hygroscopic (meaning it absorbs moisture) and has a minimum dry boiling point of 401°F (205°C) minimum and a minimum wet boiling point of 284°F (140°C). It will absorb 1 to 2 percent of water per year depending on climate and operating conditions. It is used in most domestic cars and light trucks in normal driving. It does not require cleaning the system and it can be mixed with DOT 4 and DOT 5.1 without damage to the system. The problem with it is that it absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.

DOT 4: This brake fluid also has a glycol in it but the SAE J1704 specification considers it to be a borate ester base fluid. Typically in the high performance fluids, it also contains other additives. It is clear to amber in color. It is hygroscopic (meaning it absorbs moisture) and has a minimum dry boiling point is 446°F (230°C) and minimum wet boiling point of 311°F (155°C). It is used in many European cars; also for vehicles in high-altitude, towing, or highspeed braking situations, or ABS systems. It does not require cleaning the system and it can be mixed with DOT 3 without damage to the system. The problem with it is that it absorbs moisture out of the air and thereby reducing its boiling point, however it absorbs moisture at a rate slower than DOT 3. It can also damage the paint on a vehicle.

DOT 5: This brake fluid has a silicone base. It is purple in color. It is NOT hygroscopic (meaning it cannot and will not moisture) and has a minimum dry boiling point of 500°F (260°C) and a minimum wet boiling point of 356° (180°C) It is not used in many brake applications, seeing primary duty in weekend, antique, and collector cars that sit for long periods and are never driven far. It does not mix with DOT 3, DOT 4, or DOT 5.1. It will not absorb water and will not damage the paint on a vehicle. It is also compatible with the same rubber formulations as the DOT 3, 4 & 5.1 fluids. The problem with it is that it can easily get air bubbles into the system. The air bubbles are nearly impossible to remove and result in poor system performance and poor pedal feel. Although originally developed in the late 1960's by General Electric specifically for racing, it is unsuitable for racing for a variety of reasons. If as little as one drop of water enters the fluid, severe localized corrosion, freezing, or vapor lock may occur. This can happen because water is heavier and not mixable with silicone fluids. It is unsuitable for ABS.

DOT 5.1: This brake fluid is similar to DOT 4 it has a base comprised primarily of Borate Ester. Often in the range of 70 - 80%. To meet specification, it also will contain other additives. It is clear to amber in color. It is hygroscopic (meaning it absorbs moisture) and has a minimum dry boiling point of 500°F (260°C) and a minimum wet boiling point of 356°F (180°C) minimum. It is almost exclusive to Europe, used in high performance cars. It can be mixed with DOT 3 or DOT 4 without damage to the system. It maintains higher boiling point than DOT 3 or DOT 4 fluids due to its even greater borate ester content. It is excellent for severe duty and racing applications. The problem with it is that it costs more than other fluids and there is limited availability in the USA. It also absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.


Basically DOT 4 has a higher boiling point than DOT 3, so using it your brakes might be more prone to fading.

All the best

Keith
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-Savage-
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Joined: 10 Jun 2005
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PostPosted: 19:31 - 25 Feb 2006    Post subject: Reply with quote
Thanks Smile il put some dot3 in for now, until i can get some dot4, then il have a go at bleeding/cleaning/upgrading the brakes when i have time lol
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JGY6000
Trackday Trickster



Joined: 25 Sep 2005
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PostPosted: 23:01 - 25 Feb 2006    Post subject: Reply with quote
noooo dot 3, that must be some old shit, u need dot 4 or ur brakes will fail, dont mix them what ever u do, and just becuase u see dot 5.1 dont assume its better as its a completly diff thing altogether
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-Savage-
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PostPosted: 23:08 - 25 Feb 2006    Post subject: Reply with quote
dot3 is the hydrolic fluid used in landrovers, so its good stuff. already done anyway, MAJOR improvment lol
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Guest
Brolly Dolly



Joined: 22 Apr 2004
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PostPosted: 23:08 - 25 Feb 2006    Post subject: Reply with quote
Thanks for that Keith - copied and saved for elsewhere Thumbs Up


why didn't they call DOT 5 something unique like DOT bloody useless? Smile
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 16:49 - 26 Feb 2006    Post subject: Reply with quote
Jose wrote:
noooo dot 3, that must be some old shit, u need dot 4 or ur brakes will fail, dont mix them what ever u do,


You can happily mix DOT 3 and DOT 4. And many racing fluids are DOT 3 as although they have a higher dry boiling point than DOT 4 fluid their wet boiling point is lower (not an issue when you change it regularly).

Jose wrote:
and just becuase u see dot 5.1 dont assume its better as its a completly diff thing altogether


No, DOT 5.1 is very similar stuff and can be mixed with DOT 3 and DOT 4. It is DOT 5 that cannot be mixed with the others.

Guest wrote:
why didn't they call DOT 5 something unique like DOT bloody useless? Smile


It can be quite useful. Doesn't absorb water at all so there is no need to change it (unlike 3 and 4 that absorb water like crazy), and it does not destroy paintwork. Also has a higher boiling point than DOT 3 or DOT 4 fluid. Down side is that it is VERY difficult to get any water out of the system using the stuff (which can lead to water pooling in one area causing corrosion, and also collecting in the calipers where it can boil easily) and it also tends to hold air in suspension, which then compresses and gives a softer lever feel.

All the best

Keith
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Guest
Brolly Dolly



Joined: 22 Apr 2004
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PostPosted: 21:55 - 26 Feb 2006    Post subject: Reply with quote
Kickstart wrote:
it also tends to hold air in suspension, which then compresses and gives a softer lever feel.

All the best

Keith



Most folk have enough trouble bleeding their brakes without throwing that little spanner in the works though, eh? Wink
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 21:59 - 26 Feb 2006    Post subject: Reply with quote
Guest wrote:
Most folk have enough trouble bleeding their brakes without throwing that little spanner in the works though, eh? Wink


Yeah, and we are having a pain with the ZZR600 Crying or Very sad .

By the way, to anyone bleeding brakes, NEVER shake the bottle of fresh brake fluid.

All the best

Keith
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-Savage-
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PostPosted: 22:12 - 26 Feb 2006    Post subject: Reply with quote
lol why? does it bubble up?
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 22:23 - 26 Feb 2006    Post subject: Reply with quote
Hi

Pretty much yes, brake fluid gets air bubbles easily which will make it a nightmare to bleed through.

All the best

Keith
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mr.z
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PostPosted: 23:56 - 26 Feb 2006    Post subject: Reply with quote
Kickstart wrote:
Yeah, and we are having a pain with the ZZR600 Crying or Very sad


Helped chris_biker on here do his, bloody hell they are fiddley! Shocked (thats after drilling the seized screw out of the resivoir! Rolling Eyes)

Those little bleeder things are good, but mine broke after a year, you can get a small bit of hose that has a slit near the stoppered end, only lets liquid out and not back in.. (a place down the road sells them, most car places should, it cost 98p) its a bit short but easy to extend (8mm tube and small hard tube to join them) (mine attached)

After extending you can put it in half a jar of fresh fluid and make 100% sure its not drawing any air in..

Makes anything brake related an easy simple one person job to sort (appart from those nipple related incidents Shocked )
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 00:07 - 27 Feb 2006    Post subject: Reply with quote
Hi

Tried most of the tricks. Use a Mitivac (small vacuum pump) on the bleed nipples. Cracked off the banjo bolts with the system under pressure (both on the m/c and on the splitter on the bottom yoke).

If I pump the lever repeatedly then it builds up some pressure, but that disappears if you leave the lever for a minute or 2. Not sure what the problem is. There is some expansion in the hoses but not much. Maybe enough, but they were not causing problems before (the calipers have been rebuilt with new seals and pistons).

All the best

Keith
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mr.z
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PostPosted: 00:20 - 27 Feb 2006    Post subject: Reply with quote
Sounds very odd Confused could you take the whole system off and put it in a tub of water? (ala pushbike tyre? Razz)

I know with coolant systems they use some kind of UV reactive liquid, they put it in the system, pressureise it and then use a uv tube to see where its comeing out... trouble is its bloody expensive (the stuff they use in engineering is anyways), and only usefull if you just happen to have a uv light...

Good luck getting it sorted Thumbs Up

BTW how much did it cost to have the calipers rebuilt? did you do them yourself? are they the "floating" kind or the later "pressed from both sides" kind?
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 00:30 - 27 Feb 2006    Post subject: Reply with quote
Hi

Don't think they are leaking. Just the fluid returning to the reserviour.

Seen the UV leak tests done on air conditioning systems.

Bought the seals and pistons from WeMoto to rebuild the calipers.

All the best

Keith
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