DOT 5 Brake Fluid

[BugEyeBear]

Informative Article...

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[Alredneck]

Been using the stuff in all my deuces and 5tons now for over a year with no problems. Did have to bleed the systems well but other than that no problems. DOT5 can be found all over the place so if something bad happens you can get the stuff to fix the problem.

 

[Goose2448]

I use DOT5 in my pickup and it works great.

 

[cranetruck]

Interesting comment about jelling if mixed. I had DOT5 and DOT3 in a jar for a year on my work bench and the two never effected each other, stayed separate as two incompressible liquids.
IMHO, it would even be good to have some DOT3 in the system to keep any water from freezing, but that's just my humble opinion....

I have DOT3 in my deuce brake system and no problems going on 15 years now.

 

[Jake0147]

Interesting comment about jelling if mixed. I had DOT5 and DOT3 in a jar for a year on my work bench and the two never effected each other, stayed separate as two incompressible liquids.

Have you considered (or maybe even done) a repeat of this test with DOT 3 and power steering fluid? I say that because many brands of the two come in bottles that are identically shaped and colored. That makes it a common thing to have happen.

I have also been unable to duplicate the "sludge" from mixing the two types of brake fluid, and I have seen many brake systems with mixed content.
I have been able to duplicate a "sludge" effect when petroleum based fluids mix with the glycol based fluids. Kind of like the runny mess that you find in Kleenex during allergy season.

There is also this FWIW, which does not say so in so many words, however upon reading it you will see that it is recommended to mix the fluids until it is convenient or appropriate to change over the entire hydrualic system. It also recommends against solvents to flush the system. Just brake fluid.

TB-43-0002-87 Brake Fluid Silicon (BFS) Conversion Procedures for Tank-Automotive Equipment Manual

 

[StreetbikeDepot]

I use DOT3 in my MV's too, never had a problem.

I'd rather have a brake fluid that absorbes the moisture evenly into the system than to repel it and cause the water to drop to the low area of the system (wheel cylinders) and cause rust. Ever wonder why MV's have such a problem with leaky and rusted wheel cylinders?

Since the brake system is a vented system with no rubber barrier, moisture will naturally enter the system, so the desicion is how you want the fluid to handle it.......let it pool up in the low areas or absorbe it evenly thoughout the sytem. Either way the moisture in the fluid does change the compression characteristics of the brake fluid but a pocket of water will cause more brake fade than having the moisture absorbed evenly.

 

[BugEyeBear]

Realistically we should all be bleeding our brakes regularly.
At least once a year.

Moisture gets in there, regardless of which fluid you use.
Moisture damages seals & components.
Moisture needs to be prevented by proper venting, by draining the air tanks, and by proper maintenance of the system.
Ultimately though it needs to be removed by regularly bleeding.

Bleeding also serves to remove dirt and other contaminents.

I prefer DOT 5 because it has a higher temperature capacity, is friendly to painted surfaces, and isn't toxic.


BTW: I bleed the brakes on my race cars before EVERY race. It is cheap insurance that I'll be able to stop when I need to!

 

[jollyroger]

I too have heard about the reaction between the two fluid types but have not seen it personally. I live in a dry area so water in the brake system is less of a problem for me through condensation. Not that it can't happen. Regular maintenace including bleeding the brakes is proly a good idea as Bug Eyed Bear stated.

 

[OldDominionIron]

can anybody recommend a place to purchase DOT 5 fluid in larger containers than the 11 oz. jars from Advance. I'm thinking of something in the 32 oz. range so I can bleed/flush my system.

 

[DieselBob]

can anybody recommend a place to purchase DOT 5 fluid in larger containers than the 11 oz. jars from Advance. I'm thinking of something in the 32 oz. range so I can bleed/flush my system.

Try this link. About a 3rd of the way down the page

Premium Genuine Issue U. S. Military Surplus. Including, United States Army, U.S. Navy and U.S.M.C. New Old Stock, Current Issue And Also Some Used.

 

[BugEyeBear]

Napa sells it by the gallon.

 

[Jake0147]

Realistically we should all be bleeding our brakes regularly.
At least once a year.
Moisture gets in there, regardless of which fluid you use.

That's worth saying again.

 

[73m819]

at napa dot 5 will cost you about $100 a gal., when i went to aberdeen in 06 , i went halves with a guy, we got a case( 4 1 gal) for$100. this was mil. surplus. look on ebay, ive seen dot 5 by the gal. go a lot cheaper than napa

 

[BugEyeBear]

at napa dot 5 will cost you about $100 a gal., when i went to aberdeen in 06 , i went halves with a guy, we got a case( 4 1 gal) for$100. this was mil. surplus. look on ebay, ive seen dot 5 by the gal. go a lot cheaper than napa

Yeah, Napa Online says this is $114.00 Retail at my local Napa.

So even with the "Frequent Customer" discount it is probably still somewhere in the $80.00 to $100.00 range.
MY Napa guy treats me pretty well. But he's still there to make a $$!

Napa is not the cheapest source I'm sure.
But STILL BETTER than buying 10 little bottles and paying even more for less!

Sometimes you need it TODAY.
At least Napa almost always has it in stock and you can just stop by, pick it up, and you are ready to get dirty!!

MAYBE if I planned ahead I'd think about buying large quantities in advance.
SOMEHOW I ALWAYS need something at the last minute to finish a job!!

 

[monkster]

can anybody recommend a place to purchase DOT 5 fluid in larger containers than the 11 oz. jars from Advance. I'm thinking of something in the 32 oz. range so I can bleed/flush my system.

The manerger at O'Rellys said he would get as big 1gal. for me. This may be a IN chain but larger quanities are there. He also knows my inventory of MV.

 

[BugEyeBear]

I just did a quick web search.....

5 Gallons for $191.98 (plus $7.14 UPS Ground, $13.46 UPS 2nd Day, or $33.44 UPS Next Day) = as little as $39.82 /gallon

640209 Motor Factory Brake Fluid Dot 5 Silicone 5 Gallon Drum


OR on eBay 1 Gallon for $40.00 (plus $13.01 UPS Ground) = $53.01 /gallon

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=390097099839&ssPageName=STRK:MEWAX:IT

 

[littlebob]

As far as I know the Dot 3 and Dot 4 also react with the moisture and become acidic and corrode the hydraulic componets in the brake system. The moisture in the 3 4 systems gets boiled out and works out OK in a vehicle that is used regularly, and The Dot 5 doesn't.
I use the Dot 5 because Mine doesn't get much use, but would use 3or4 if I used it more.
There are plenty of threads to be found on this site that probably go into more detail.

 

[BugEyeBear]

Any moisture that somehow remains isolated in your brake system (usually induced via condensation) can boil at 212degreesF.
BUT this water then turns into steam, thus resulting in AIR in the brake system.
NOT GOOD!

Also...
Just a 3% water content in your brake fluid will lower the brake fluid's boiling point by approx 30%!!

Bottom line...
Moisture will get into your brake system.
Moisture in a brake system is BAD, both from a brake syetm performance point of view and a corrosion point of view.
You should do what you can to keep it out, but ultimately you simply need to bleed regularly to get it out and preserve your brake system integrity.


ONE OTHER ITEM WORTH NOTING:
Silicone Based brake fluid is roughly 2X more compressible than Polyglycol Ether Based brake fluid. This results in an increased "spongy" pedal feel even when air has been bled from the system.

Every solution is a bit of a trade off between good points & bad points.....

 

[OPCOM]

It is worth saying that DOT5 will lose its purple color over time, and therefore the water+fluid test should always be done when it is not certain what is in the system.

 

[mikeyapproved]

My 2 cents?

Most of this has been covered already, but a review and my opinion:

DOT 5 Good and Bad
Good because the boiling point won't get lowered throughout the system, as it is Silicone based so it does not absorb water.

Bad because it is silicone based and won't absorb water. Therefore the water that forms in the system gets trapped in low areas and will rust that area from the inside out. It also will freeze in that area. It also will boil very easily in that area and cause steam which will cause a very spongy pedal and possible loss of brakes entirely. Also because DOT 5 has a much lower viscosity , air can fit in between the molecules of the fluid, again causing a spongy pedal and trapped water ( air has water in it)

I see way more BADS than GOODS for most applications with DOT 5...

DOT 4 Good and Bad
GOOD Has initial higher temperature boil point and is more stable than DOT 3 . Will absorb water, so annual complete bleedings will remove all the water from the system.

Bad It's initial stability and higher boil point falls off faster than DOT 3 fluid, so unless it is changed often, it is actually worse than DOT 3 in the long term.

DOT 3 Good and Bad
Good It is more stable in the long term and keeps it's specified boiling point longer than DOT 4. It is easy to find and inexpensive. It also absorbs water, so regular changes of fluid get rid of this contamination.
Bad is that initially it may have a lower boiling point and be less stable than DOT 4

DOT 3 is the best choice for those who do not want to change the fluid as often... This is one reason why many manufacturers still specify DOT 3. It stays better longer than either DOT 4 or DOT 5...

Ok, another point on bleeding. If you bleed your own brakes, DO NOT use a pressure bleeder unless it is the type with a diaphram or piston between the pressure and the actual fluid. Otherwise air is injected into the fluid when bleeding and this adds bubbles and water right from the start!

Then the point about fluid storage.... Buy your fluid as you require it, don't buy bulk as the fluid (DOT 3, 4 and 5.1) will absorb water from the air in the container and cause trouble before you even start using it.

Ok last point on brake fluid and water absorption. The rubber parts, seals, master cyl cover diaphram etc actually let water through them in very small amounts over time, so again, CHANGE YOUR FLUID REGULARLY!

mikey.