Which brake fluid should be used? DOT 3, DOT 4, or DOT 5.1?

[94Eddie]

Flushing all brake fluid is not normal or at all easy. To change to the silicone DOT 5 would be very difficult.

For practical purposes, not changing to DOT 5, it isn't needed to be pushing all the pistons back completely, or cycling the ABS module. Just make a point to fully bleed all four corners at least every couple of years.

When changing pads, it is not proper procedure to compress the pistons without the bleed screws open, that pushes old fluid back into the ABS module, which is the most fragile part of the brakes, and most expensive. The right way to do it is to attach a bleeding hose to the bleed screw, before compressing the caliper pistons. That lets the oldest fluid inside the caliper out first. Then bleeding the brakes after the pads are in gets new fluid through there and any air out that got in by opening the bleed screw.

I gather on another forum about brakes that the Ate fluid is possible to buy the blue fluid version of still, from an international seller. I liked that along with their clear fluid, to help with bleeding. The USA regulations made the blue fluid unapproved many years ago, racers love it for bleeding brakes as I point out, regulations are excessive here.

My plan is to bleed the line and then compress the caliper and bleed the line again. Not as much as the initial bleed but enough to remove any backed up fluid from compressing the caliper.

 

[CDW6212R]

The fluid that will remain or is hard to displace is what is deep inside the ABS(that's a very tiny amount), and the small amount in each caliper that is mixed with new incoming fluid from the hose. If getting the most out is the goal, I'd do that flush after a full both end brake job. Open the bleed screws for compressing the pistons for new pads, and then bleed the system next. I'd do the rears first so the back would be fully bled before going to the front. The fluid quality is important to the extent that you don't want low end brand fluid. Any middle level to top shelf brands will be fine for everything except real racing etc.

When you flush the fluid regularly, you tend to notice other items which need care, like old brake hoses or suspension parts. People should try to do their own brakes, just as a method of discovering potential future car issues for themselves.

 

[Bazz270]

you can bleed gen 4 ABS via IDS or Forscan anytime.not a problem at all

 

[Nikola]

There is a video on the german ATE website, where a specialist explains, why not to use DOT 4 in a DOT 3 brake system.
He says, it's because of boric acid ester in DOT 4 and 5.1 brake fluids, which is able to destroy rubber parts in DOT 3 brake systems and could so lead to a complete brake failure.

I have a similar experience with putting DOT 4 in my 94 Explorer clutch system. Almost immediately gradually start to liking from the slave cylinder, and also start to lose pressure in the clutch system. At first, I didn't connect with DOT 4 and continue to fill and use and prepare to change the slave cylinder (everybody knows that is a "heavy" operation). But, in the moment of lucidness, I just flush again with DOT 3 ( same manufacturer) and the problem disappear, with no pressure loss and especially no liking (never until today, 6 years 90.000 km). After that, I always use only DOT3 in the brake system also.

 

[Bazz270]

Strange

Never had any problem with using dot4 on dot3 vehicles

Also checked with Chevron,acdelco and pensoil support that Dot 4 fully compatible with dot 3 systems.

ATE site claims that DOT4 fluid fits DOT3 specs too:

Can you please specify what polymer seal material degrates with boric acid?

 

[FATK]

Flushing all brake fluid is not normal or at all easy. To change to the silicone DOT 5 would be very difficult.

For practical purposes, not changing to DOT 5, it isn't needed to be pushing all the pistons back completely, or cycling the ABS module. Just make a point to fully bleed all four corners at least every couple of years.

When changing pads, it is not proper procedure to compress the pistons without the bleed screws open, that pushes old fluid back into the ABS module, which is the most fragile part of the brakes, and most expensive. The right way to do it is to attach a bleeding hose to the bleed screw, before compressing the caliper pistons. That lets the oldest fluid inside the caliper out first. Then bleeding the brakes after the pads are in gets new fluid through there and any air out that got in by opening the bleed screw.

I gather on another forum about brakes that the Ate fluid is possible to buy the blue fluid version of still, from an international seller. I liked that along with their clear fluid, to help with bleeding. The USA regulations made the blue fluid unapproved many years ago, racers love it for bleeding brakes as I point out, regulations are excessive here.

Hi Don, I liked your response and it seems logical. I am not using DOT 5 in my Dad's 96 Explorer. The manual called out DOT 3. I have though pushed the pistons back all the way taking special care not to damage the rubber boots. If no one has added fluid to the system it all going back to the master cylinder reservoir. When I get all the brakes finished, I have my wife pump the pedal with all the bleed valves open while I keep an eye on the reservoir level. I have her stop with the pedal completely depressed while I check the fluid in the clear hoses I attached to the bleed valves. I use a 10mm hose. When all the fluid is running clear I shut the bleed valves down one at a time starting with the driver front. I make sure to keep the reservoir full and the pedal down when I close them off. I then go the the passenger front, then driver rear and finally the passenger rear. I then feel the pedal for stiffness. Usually it is rock steady. I have never experienced any issues doing this but, then again I have not seen where it says I shouldn't back flow the ABS system. My thought is that due to the brake system being a dead ended single acting hydraulic system, the fluid never gets exchanged with new fluid when you applied the brakes. Therefore you get a build up of wear particulate in the lines and pistons. With that being the case I have to assume that the "McPherson Curve" applies to the wear factor. Look it up online. www.filtermagindustrial.com It is very interesting and I have actually seen this in many hydraulic systems. I design hydraulic and control systems for my company and I make sure that I do not end up with an area of the system that the fluid does not get exchanged. If the fluid does not get exchanged we end up seeing premature seal wear in the actuators. Let me know if there is something that I could damage by flushing the brake system about once a year or so. I would be interested so that I am not going to mess something up. Thanks! FATK

 

[FATK]

I have a similar experience with putting DOT 4 in my 94 Explorer clutch system. Almost immediately gradually start to liking from the slave cylinder, and also start to lose pressure in the clutch system. At first, I didn't connect with DOT 4 and continue to fill and use and prepare to change the slave cylinder (everybody knows that is a "heavy" operation). But, in the moment of lucidness, I just flush again with DOT 3 ( same manufacturer) and the problem disappear, with no pressure loss and especially no liking (never until today, 6 years 90.000 km). After that, I always use only DOT3 in the brake system also.

Very interesting. On the one bottle that I had it said DOT 3-4 and it said it could be used in a DOT 3 or DOT 4 system. I sure hope I don't have a problem. At least most of it is DOT 3.

 

[MakinJeepsWeep!]

I use dot4 synthetic just because it resist the moisture a bit better, other than like i saw mentioned your not gonna use your brakes in a way to need any better. Get some all ceramic pads and fresh rotors follow the brake in procedure to the letter and let the go. I first tried this set up on the 06 Merc witch came with ceramic pad(from some info i have read) did the fluid new rotors pads calipers and lines and it has worked flawlessly since and the brakes have lasted forever. Hope that helps with someone to decide.

 

[CDW6212R]

The ABS module are made with a main passage that goes around most of the internal valves etc, but not all of them. The system has valves which **** off flow so the ABS when operating properly, can control(limit) the brake force. All that really means is that normal bleeding procedures will move fluid through the common ABS path, not through some internal passages that are used for the ABS function.

So normal fluid draining or bleeding or pumping, moves old fluid up past the ABS, or down past it(air bleeding etc). That just means that you might end up with dirty fluid up above the ABS, even a tiny amount, by compressing the pistons. Virtually never will the fluid just below the ABS be so filthy that a small amount pushed up beyond the ABS will cause trouble. That would be most likely with systems with very old fluid in it, and someone does a brake job without opening the bleed screws at all. As long as you do some bleeding at decent intervals such as one or two years, getting something into the ABS is very remote.

Having clean or fresh fluid is more important than the type(DOT 3 or DOT 4 etc), so try to have that done often enough to avoid issues with fluid. Buying a car that has sat for years, is the one to worry about; change the fluid completely, quickly.

 

[LorenzoGarbanzo]

I flushed all 4 wheels with fresh dot4 a year ago when I had a caliper fail and it's been fine. I was advised dot5 could cause issues due to a reaction with old fluid.

 

[Bazz270]

According to updated FMVSS brake systems (not the clutch systems)practice, brake fluids made from the same chemical base (including any kind of additives) wont harm any seals,hoses,metals or other brake system component.

Vehicle made in 1994 probably used an old type of seals degrated from DOT4 brake systems additives or FMVSS practice claims something else about clutch systems.

Anyways.Cars made after 2000 shouldt have any problem with mixing between DOT3 or 4 since it is the same seals used in both brake systems