Replaced brake fluid

[AKA EDDY]

I just replaced the brake fluid on my 2008 Backdraft #648. It has 12,500 miles on it and had Dot 5 fluid in it. I replaced it with Dot 3 - 4 fluid. The original fluid was dirty and had some "gel" in it. I found out that when filling the reservoir, if the fluid is a little low, approx. 1 oz, the red warning light comes on. I also discovered that on the dual reservoir, the front chamber is for the rear brakes and the rear chamber is for the front brakes...go figure. Hope this will help someone.

[vatdevil]

What's required to convert a brake system to DOT 3/4? Flush with alcohol ? Replace seals?

[patrickt]

Originally Posted by vatdevil

What's required to convert a brake system to DOT 3/4? Flush with alcohol ? Replace seals?

I'm curious about that as well. I have never even heard of anyone going from DOT 5 to DOT 3/4. Just performing a "good flush" ain't gonna do it.

[AKA EDDY]

I used a vacuum bleeding system to remove the original fluid and flushed about a quart of Dot 3 - 4 through the system until the fluid was clear. It's been a couple of hundred miles with no problems.

[jimbo01]

Converting from Dot 5 which is silicone based to Dot 3 or 4 can be a real problem. I don't know who installed the Dot 5 in the car to start with. The system must be clear of any sign of the Dot 5 prior to installing the dot 3-4. Same thing must be going the other way. The two fluids don't mix.

[Tim7139]

Originally Posted by patrickt

I'm curious about that as well. I have never even heard of anyone going from DOT 5 to DOT 3/4. Just performing a "good flush" ain't gonna do it.

That's because it is not suggested and is not considered safe. You cannot remove all the Silicone fluid. At the very least, I would talk to a specialist as well as flush out the system a few times.
Among the issues are that seals suitable for silicone are thought to be incompatable with DOT 3,4 systems.

[Cashburn]

The DOT 5 in the Backdrafts was abandoned a very long time ago. Was your fluid purple? That was the way to tell back then.

[bobcowan]

That could be a problem. When you mix the two, they clot. Not a good thing in a hydraulic system.

I keep hearing that seal material can be incompatible, too. But have never seen that companies sell different seals depending on the fluid used.

Ideally, you should completly disassemble the system and clean it out. Rebuild the MC's and all the calipers. Flush the heck out of the lines to prevent clots.

[andronikos]

How can we tell what fluid it has? Mine is purpule? So, is this DOT 3,4,or 5?

[FredG]

I believe Jay posted above that purple indicates five.

[BDR_Boy]

I used DOT 5 in a C3 Corvette many years ago when I did a complete overhaul of the brake system, and it was indeed purple. Thinking that’s done so one can tell the difference… but can’t say for sure, as that was the only time I used it.

[FredG]

Just watched an episode of hand built hot rods on motortrend and this was exactly the issue they ran into. Older Custom Corvette with a mushy brake pedal. Brake fluid with pink because the two were mixed. They wound up replacing the calipers after flushing out the brake lines with gallons of clean fluid. I do remember my old 66 Vette using silicone brake fluid. They reiterated that mixing the two was a big No-No.

Fred

[tocheck]

The way I checked mine was mixing some fluid with a little water in a container and shaking it up and then letting it settle out. Dot 5 is silicone based so will not stay mixed. Dot 3 and Dot 4 should stay mixed with the water.

I am no expert, just what my research found.

[ront49]

Originally Posted by jimbo01

Converting from Dot 5 which is silicone based to Dot 3 or 4 can be a real problem. I don't know who installed the Dot 5 in the car to start with. The system must be clear of any sign of the Dot 5 prior to installing the dot 3-4. Same thing must be going the other way. The two fluids don't mix.

That's right, I have a 2004 BDR build #151 and according to Backdraft, it came with DOT4. When my clutch failed to work, I drained the brake /clutch fluid out. It was more like gel. TOO much heat because it is located directly over the header...it was so hot, I burnt my fingers. I saw some guys wrapped their header with insulation and some added a heat shield above the header. The car had about 4500 miles on it. Kept pumping the goop out until it ran clean then refilled with DOT 4. Works great now.

[Jerry Clayton]

Water / condensaion--------- mixed with brake fluid lowers the boiling temp of the fluid-so some that is good for say 500 degrees is lowered to 350*? of worse----------the military back many decades ago had problems of water in brake fluids and speced the Dot 5 because of the vehicles stored in strateit? places arond the world--------However for performance type vehicles there are some extremely hot areas around the differant portions of the braking/clutch systems-------and Dot 5, which won't mix with water,well, the water boils at 212* and of course your brake/hydraulic clutch system is burnt toast-----------its better to have a milky substance that boils at 500* than something with water in it that boils at 212* when you need to stop------or slow down -------Happened to me in the command vehicle of a very long military convoy on a pretty sharp downhill curve ----------but I haddened had any signs of trouble after submerging the M151 in that stream the day before---------

[GLS-BDR226]

Originally Posted by ront49

That's right, I have a 2004 BDR build #151 and according to Backdraft, it came with DOT4. When my clutch failed to work, I drained the brake /clutch fluid out. It was more like gel. TOO much heat because it is located directly over the header...it was so hot, I burnt my fingers. I saw some guys wrapped their header with insulation and some added a heat shield above the header. The car had about 4500 miles on it. Kept pumping the goop out until it ran clean then refilled with DOT 4. Works great now.

My clutch fluid was DOT 3 but my brake fluid was DOT 5. I’ve never attempted to convert my brake fluid from DOT 5 to DOT 3/4 because of the aforementioned issues. I wish it was easier but I don’t want to rebuild my entire brake system. It works fine now. This is on 226.

[FredG]

I have been following this because like many older Backdrafts, I have DOT 3/4 for the clutch and DOT 5 for the brakes. I have no issues with my brakes so am I correct in assuming I should just leave it or am I looking at issues down the road with the DOT 5. Thanks


Fred

[Bricklayer]

Hi Guys, First time poster here! I run my Hi-Tech with Dot 5 for the brakes and Dot 3 for the clutch only.

[bobcowan]

Originally Posted by FredG

I have been following this because like many older Backdrafts, I have DOT 3/4 for the clutch and DOT 5 for the brakes. I have no issues with my brakes so am I correct in assuming I should just leave it or am I looking at issues down the road with the DOT 5. Thanks


Fred

You've been driving it like that for years. No sense changing it now.

DoT 5 is not recommended for 2 reasons. First, it's compressible. That means you'll get a little bit of a mushy pedal. Not much you can do about that.

Second, it's hydrophobic. Any water that gets in the system will not mix with the fluid, leaving small puddles and reservoirs of water in the system. Any metal components exposed to water will oxidize. When water gets into the calipers, it will turn to steam at relatively low temps. That's bad.

The easy way to prevent that is to completely flush the system with new fluid as a routine maintenance step.

As you flush, take a close look at the fluid. If it has tiny particles in it, something ion there is rusting and heading for failure. You'll have to take the whole system apart to find it all.

[FredG]

Thanks Bob.

As it turns out I don't have DOT after all, It just looked purple through the opaque reservoir. Thanks for the input.

Fred