Dirty Howie

Is all DOT 4 brake fluid the same or not ??
Is it all SYNTHETIC no matter what the bottle says ??

I had a shop change from stock DOT 3 to DOT 4 a while ago...and I don't know the brand used.

I recently bled the brakes and used a whole can of Prestone DOT 4. When I went to get more yesterday I noticed the Prestone bottle said Synthetic for DOT 3 or DOT 4 repclacement. It states good to 500* temp.

I bought a big bottle of GUNK DOT 4. It doesn't say synthetic and only says its good to 466* temp. Supposedly GUNK makes all kinds of products inlcuding Liquid Wrench or WD40.

Am I safe with this stuff or not...................


DH

rws.1

Not necessarily...
Some manufacturers get to DOT 4 with glycols, others used borated esters... ( sort of a super DOT 4)

But all DOT 3 and DOT4 are compatible.

See these links as a resource
http://www.xs11.com/tips/maintenance/maint1.shtml

http://www.stoptech.com/tech_info/wp...fluid_1a.shtml

Dirty Howie

Thanks for the links.....read most of it.

Sounds like any DOT 4 is ok as long as your not boiling the fluid with hard enough braking. And also bleeding frequently which I plan on doing.

Was interesting that Stoptech site recommended buying smaller containers to avoid water absorption.......

Think I will take back the big bottle and get a couple of smaller ones. And since the Prestone worked VERY well at my last track event which is hard on brakes I will just stick with it


DH

Barrier

You might want to try Ford High Performance Brake Fluid. Ford fluid has been reported to have one of the higher boiling points. I have been using it for years in both cars and Motorhomes ( I first heard of it in a Motorhome Forum). Price is really good, about $3. or so at Ford dealers.
Someone also mentioned it on this forum a couple of days ago.
Barrier

turboc5

As far as easaly store baught brake fluid, I like the vavoline synpower. It has the highest boiling point I have found at a auto parts store. As far as the bottles, Big ones are ok as long as you use it as soon as you open it. After that throw it away, don't put it back on the shelf. Even with the cap on its not 100% sealed. Try to keep it open to the air less than a hour or so. Preferably not on a humid day. Believe it or not but the plactic some times can be porous enough for moisture to go through the bottle. Polyglycal is a magnet for moisture and moisture+heat=steem=fade

J Ritt

When we open a bottle of fluid, we always write the date on it with a marker. If it sits for a month or more cracked open, we dispose of it, rather than put it in to one of our test vehicles or customer cars. Definitely makes sense to use 500ml bottles, rather than a giant tub of fluid.

Dirty Howie

How about all the fluid that sits in the master cylinder resevoir. That cap certainly isn't air tight.........


DH

AU N EGL

Here is some info I found on DRM's web site.

"A number of automobile design changes have occurred in recent years which directly or indirectly affect the braking system. The major influence on design changes has been for fuel economy. Drastically modifying the vehicle aerodynamics and design reduces turbulent air flow under the vehicle to lower the wind drag factor. Unfortunately this also results in a reduction in cooling air past the brake discs and drums. This potentially translates to significantly higher brake fluid temperatures in the wheel area. Improved aerodynamics and engine turbo charging have served to increase under hood temperatures. This will increase the temperatures in all brake components, from master cylinder to the rotors and drums. Front wheel drive vehicles and smaller lower profile tires equally increase brake fluid temperatures. (8)

The boiling point of new DOT 3 brake fluid is 401 degrees Fahrenheit. Contaminates such as moisture, dirt and corrosion greatly reduce the boiling point of brake fluid. High temperatures encountered in ABS disc brake applications require hydraulic fluid specifically formulated to withstand the higher temperatures than normally experienced in drum type brakes. Modern hydraulic brake fluids are designed for high boiling points because of the extended temperature ranges prevalent in disc brake service. Small amounts of contamination such as foreign material, vapor and water greatly decrease the boiling point. When the service temperature exceeds the reduced boiling point, contaminated brake fluid will vaporize and prevent positive braking on the subsequent application. Besides materially reducing the boiling point, moisture promotes rust in steel brake lines, sludge in cylinders and corrosion inside wheel cylinders and calipers.
"

Brand Wet Boiling Point Dry Boiling Point
Castrol SRF 518°F 590°F
Motul RBF600 420°F 593°F
AP-600 410°F 572°F
ATE-Super Blue 392°F 536°F

Valvoline 333°F 513°F
Castrol LMA 311°F 446°F
Ford HD 290°F 550°F
Wilwood 570 284°F 570°F
PFC-Z rated 284°F 550°F
AP-550 284°F 550°F

IMHO always use the WET not dry boiling points for comparison. and that one should never use any brake fluid that has a wet bloing point below 400* for any racing or track time

Brake fluid can become contaminated with water very quickly. Once the seal on bottle is broken that bottle must be used. Any remaining in that bottle should be discarded.

Water contamination occures with in 90 days in any brake system. a 3-4% contamination is concideard the WET boiling point. any why useing the WET boing point number is more important then the dry bp.

Brake fluid must be changed for each track event. not bleed but flushed. Most clubs say with in 30 days, I highly recomend within a week prior to the event. In most cases the weekend before the event to prep your car for track time.
The idea of using you vette as a DD monday though friday and showing up at the track Sat morning and expecitng your car to run flawlessly is crazy and unsafe.

I change my DD & tow vehical brake fluid 4 times a year and before any long tows. On my wifes vette also 4 times a year. These vehicals I use the Castral LMA.

On my track vette I use Castral SRF.

2kbluestreak

Valvoline Synpower is pretty cheap at $5 per quart, and that's how much I use to bleed my system right before a trackday; pretty cheap insurance. The big unknown in this situation is how much moisture gets absorbed by the fluid in the brake system. How much occurs in those few seconds when the bottle cap is off and you're pouring into the master cylinder resevoir. Then how much if the car is just sitting for a couple days or being driven to the track. If it's very little, then your boiling temperature is going to be fairly close to the dry value. For the rest of the vehicles in the world that are simply driven as transportation, most never have their brake fluid changed. Is there a maximum amount of H2O that the DOT 3 can absorb? Then is the "wet" value the same as that advertised? The brakes on these cars are hardly ever used hard, and one panic stop is not going to heat them enough to boil the brake fluid. However, if you're doing spirited driving on the street or on a track, you need the safety margin of fresh high temperature brake fluid.

kg54trains

Gentlemen;
remember that this product sits on a self for a long period of time with no expiration date or a manufactured date. True, once the bottle is open there is where the comtamination of the product with air will start. I would not disgard a nearly full bottle and I would close the bottle with plastic wrap between the bottle and cap. This will assist with the seal. If the bottle has been used and the amount of product used is now open air inside the bottle it is your choice about any continued contamination. If it sits for a long period it maybe a problem, but service shops use brake fluids that are ecomony to scale. They buy in bulk and use the larger bottles.
Buy what you are going to and date any bottle that has product left for future use and evaluation.

AU N EGL

And that is one reason to look at the WET not dry boiling points. i.e. brake fluid is most likely saturated 4% water when you buy it.

Cobratei

I wouldn't do that ( get small bottles) unless you plan to only need a small amount of fluid.
If your going to flush the system (which should be done every 3 years or 30,000 miles.) Just get 1 quart. You will use most of it and put the remaining fluid into a small pint bottle.

leadfoot4

YES, you'll use most of the fluid, but NO, do not save it, as it's been exposed to moisture, as soon as you opened the container.....

punz

Agree with what many have said. I've been using ATE Type 200 Dot4, flushing at least once a year, when not tracking. It's reasonably priced but kind of hard to find in stores. I usually order it from inter web or get it at the Tire Rack when there. Always flush before a road track event, probably the cheapest prep you can do and who wants to chance brake failure.

grinder11

I have never changed my brake fluid, or bled the ABS system or any of the rest of the system. Fluid still looks OK. I've never had any problems with the ABS, or any other part of the braking system, except the Ebrake cables. I still have the original pads and rotors, too. Maybe I'm wrong, but sometimes I think we try to do too much preventive maintenance, as in 2000 mile oil changes, etc.

Gordy M

Are you doing any autocross or HPDE events. I had a friend who was an excellent driver for Autocross and W2W events but a poor mechanic. He lost his brakes on a lap at Gingerman and boiled his fluid prior to turn one. Trying to make a left turn at 120+ doesn't work and we had to load the car on the trailer. For $20 you can change the fluid cheaply, rather than a $3600 repair bill.