Flushing brakes

[MaineShark]

What's the best procedure for replacing the brake fluid? I want to get the old fluid out, and put in new, since I plan on replacing the existing fuild with DOT-5 silicone, and I hear you aren't supposed to mix DOT-3 and DOT-5.

Actually, for all I know, it already has DOT-5 in it, but I have no way of knowing which the previous owner used, so I figure I'm safer just replacing the fluid, unless someone knows a way to test which is in there already?

Joe

 

[80convertible]

Why did you decide on Dot 5 fluid?

Jim

 

[resto75]

I just rebuilt all my brakes and just replaced the brake fluid with Valvoline dot4. I thought about the dot5 too but decided not to use it. I believe you have to flush the whole system with denatured achohol to get rid of all the prior fluid. If you dont get the old stuff out it turns to a gel ( or so they say).

I figure if I drain and replace the brake fluid every few years it will be fine.

 

[80convertible]

Resto,

I just purchased Valvoline dot 4 myself for my wife's volvo and my vette. The reason I asked about the decision to use Dot 5 is that there is a lot of debate about it's use in a street car. I don't personally have any desire to use Dot 5. Contrary to popular belief, water still accumulates in the brake lines. Because it is hydrophobic, the water will accumulate in one spot...the lowest place in the brake line. Some claim dot 5 gives a spongy feel to their brakes. I agree with you that a quality dot 4 flushed every few years works great. One advantage of dot 5 is no damage to paint if you drip.

Jim

 

[DDLS3]

Joe,

It's difficult to make certain that all the DOT-3 fluid is out before you change to DOT-5. The two, if mixed can solidify and plug a brake line or freeze a caliper. As was said, I don't know of a real good reason to switch to 5 as eventually moisture will find it's way in regardless. The heating/cooling cycles combined with occasional use, cause moisture to accumulate vs being driven off by more frequent use. DOT-4 has a higher boiling point. This is only important if you run autocross, or race, and use the brakes heavily causing heat to build in the system. Fresh fluid, whether DOT-3 or 4, with the brakes properly bled will give excellent braking.

 

[MaineShark]

Yeah, I reached the same conclusions, after some more thought.

So, I bought some DOT-3.

A new problem appeared, though: only one of the four rear caliper bleeder screws will move - the other three are frozen in the calipers.

I tried Liquid Wrench and some tapping with a hammer, but no joy. So, tomorrow I think it may be time to try some heat.

Joe

 

[JohnZ]

DOT5 silicone fluid loses its characteristic purple color over time, and becomes amber, like glycol-based DOT3/DOT4. To test what you have in there now, take about 1/2-ounce out of the master cylinder and put it in a small glass jar (or a test tube) with an equal amount of water, shake it up, and then let it sit for a few minutes. If the resulting mixture looks normal, it's DOT3 or 4; if it settles into two distinct layers, with the water on top (it's lighter) and the brake fluid on the bottom, it's DOT5 silicone. Do this before you do anything else so you know what's in there - you do NOT want to mix the two types in your brake system.

 

[80convertible]

Joe, when I replaced my calipers I put a dab of anti-sieze on the bleeder screw threads for future bleeding. I think someone makes s/s bleeder screws...possibly Vette Brakes. Hope your bleeder screw does not break in the caliper...fun!

Jim

 

[MaineShark]

Well, I got the brakes bled, and four new bleed screws installed (with some teflon on the threads, to help keep them from seizing).

Just like they were, before I took it to the shop. Needless to say, I will be having some words with the service manager about the skill level of his technicians.

Joe

 

[Bullitt]

Ford, believe it or not, makes a great high performance fluid that is usually less money than other "performance" brake fluids. Give it a try and make a friend of the local Ford parts guy.

--Bullitt

 

[smurfvet]

MaineShark, get yourself a set of those little neoprene caps that fit over the ends of the bleeder screws. They stop water and dirt from getting into the inner port on the bleeder screw, which can cause them to rust in place. The never-seize on the screw threads is a very good idea too. That way, you will always be able to get the screws out- easily. If you drive in the rain or have a chance to get the car good and wet, these tricks help keeping the bleeders operable over the long run.

I used the silicone fluid before, and went back to the DOT4 heavy duty fluid. The story I heard way back when was that the silicone fluid is better suited for cars that sit for a long period of time and get little use, like a museum. I agree with the comment that the silicone has a lower boiling point. I do know that with three classics in the barn, even with driving occasionally, the DOT4 systems need attention every couple of years. Anybody have any info or comments on this?

 

[vigman]

No need for 5 in a street car

Just stick with the 3 or the 4 and flush em every 2 years or so...life will be good.

Vig!

 

[Corvette-Pilot]

DOT-4 has a higher boiling point. This is only important if you run autocross, or race, and use the brakes heavily causing heat to build in the system. Fresh fluid, whether DOT-3 or 4, with the brakes properly bled will give excellent braking.

Question??
Several of you have stated using dot3 over dot5.
If you chose dot3 why did you skip on the dot4?
I would think better safe than sorry in this case.

Just dun know

 

[smurfvet]

For the cost differential between DOT3 and DOT4, at least what I've seen up here, the DOT3 will work for me.

If I was going to autocross or "drive hard", DOT4 might be a good choice because of the higher boiling point and reduced moisture capacity, but for a "driver", 3 is good enough.

 

[JohnZ]

DOT3 is standard factory fill fluid for every new car on the planet (except the Viper, which uses DOT4).