Replacing Dot 3 Brake Fluid with Dot 5
#89140
07/15/08 08:16 PM
07/15/08 08:16 PM
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charge70
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I want to replace the Dot 3 brake fluid in my 69 Dart with Dot 5.I know I have to flush the lines as the two fluids aren't compatible.My question is this,what do I use to flush the system so it won't ruin any of the hoses or wheel cylinder rubber parts.The steel lines are fairly new,and I don't want to replace them.Thanks in advance, John.
1970 Dodge Charger R/T S.E.
1969 Dodge Dart GTS 440 M-Code
1970 Dodge Charger 500 383/4-speed w/A.C.
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: Lemon_Twist]
#89142
07/15/08 10:15 PM
07/15/08 10:15 PM
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Joined: Jan 2003
Posts: 5,791 Hamilton, Ontario Canada
Magnum
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If this helps I did the same as LemonTwist.
Used the silicone fluid to push out the old Dot 3.
It was about 6 years ago on an already "aged" braking system and is still working perfectly.
69 Super Bee, 93 Mustang LX, 04 Allure Super
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: charge70]
#89144
07/16/08 03:36 AM
07/16/08 03:36 AM
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Joined: Dec 2003
Posts: 23,273 Here
jcc
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What is the reason for going 5.1 when there are some pretty highly rated DOT 3's on the market?
" All sorts of things can happen when you are open to new Ideas" Inventor of Kevlar
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: 471Magnum]
#89147
07/16/08 08:09 AM
07/16/08 08:09 AM
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Joined: Feb 2003
Posts: 4,204 Fort Worth, TX
Clair_Davis
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There are a bunch of other threads on brake fluids, and lots of good info in those threads as well. As for the high-rated DOT3 fluids, they must have low wet boiling points or they'd be DOT4's or DOT5.1's (assuming they're not silicone based). You CAN have very high dry boiling points in a fluid that only meets DOT3 specs because the wet boiling point is so low. Many of the highest dry boiling point fluids are SUPER hygroscopic - they suck moisture out of the air like it's giong out of style. Racers can feel the difference in their brake fluid from the start of the race to the end, and these fluids get changed out (or should) for every race. Clair
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: jcc]
#89148
07/16/08 09:26 AM
07/16/08 09:26 AM
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Joined: Jul 2003
Posts: 2,344 Cincinnati, OH
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Quote:
What is the reason for going 5.1 when there are some pretty highly rated DOT 3's on the market?
Just to be clear 5.1 is not a silicone fluid like dot 5 is; dot 5.1 is "traditional" with a higher boiling point.
5.1 will suck moisture, and will damage paint!
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: 6T6Cuda]
#89149
07/16/08 10:03 AM
07/16/08 10:03 AM
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I use DOT 5 at the expense of a firm pedal. The DOT 5 is a little spongey no matter how much I bleed it.
The fluid is expensive too but I have some master cylinder cover sealing issues and would have lost lots of paint had it been DOT3.
2017 Contusion Blue Challenger T/A 392 M6 "BLKNBLU"
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: Black_Sheep]
#89151
07/16/08 11:27 AM
07/16/08 11:27 AM
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Both cars I ran it in were manual brake cars. I bled them every which way and always the same.
2017 Contusion Blue Challenger T/A 392 M6 "BLKNBLU"
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: 471Magnum]
#89153
07/16/08 04:01 PM
07/16/08 04:01 PM
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Joined: Nov 2007
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cogen80
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Quote:
Unlike DOT 3, DOT5 is not hygroscopic (ie does not absorb water). Your brake system components won't rust over time making it good for cars driven infrequently (like collector cars).
you will need tyo bleed the system from time to time because the moisture will gather at the ends of the system (calipers/wheel cylinders) since the fluid won't absorb it. no big deal though if you bleed them once a year or so.
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: 471Magnum]
#89154
07/16/08 05:07 PM
07/16/08 05:07 PM
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Joined: Nov 2004
Posts: 1,128 Tulsa, OK
73cudaproject
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Quote:
Quote:
Just to be clear 5.1 is not a silicone fluid like dot 5 is; dot 5.1 is "traditional" with a higher boiling point.
5.1 will suck moisture, and will damage paint!
Do'oh! I should have known that "point 1" was there for a reason.
So none of the reasons I listed are valid. Not sure why you would use DOT 5.1 in anything other than a race car.
Don't feel alone! Thankfully I learned something today and not the hard way...
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: 73cudaproject]
#89155
07/16/08 07:16 PM
07/16/08 07:16 PM
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Joined: Apr 2005
Posts: 4,956 new berlin wisconsin
Mr T2U
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some info ALL BRAKE FLUIDS ARE COMPATABLE with each other.
silicone brake fluid retains AIR like standard brake fluid hold moisture. the best way around this is to place the black brake fluid bottle in the hot sun for about 1 to 2 hours, this is why it is delivered in black bottles. this will force the air out of the fluid. if you don't do this you will never get a hard brake petal no matter how much you bleed the system. also NEVER use silicone brake fluid in a anti-lock bracking system.
perception is 90% of reality
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: jcc]
#89157
07/16/08 07:37 PM
07/16/08 07:37 PM
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Mr T2U
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they will mix and not jell. you can put DOT 3, 4 & 5 together and your brakes will still work.
you can just suck out the old brake fluid from your master. install new fluid to pump out the old stuff with no bad side effects. there is no need to flush your brake system with anything before changing fluids.
Last edited by Mr T2U; 07/16/08 07:41 PM.
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: Mr T2U]
#89158
07/16/08 07:41 PM
07/16/08 07:41 PM
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Joined: Nov 2004
Posts: 1,128 Tulsa, OK
73cudaproject
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Quote:
some info ALL BRAKE FLUIDS ARE COMPATABLE with each other.
silicone brake fluid retains AIR like standard brake fluid hold moisture. the best way around this is to place the black brake fluid bottle in the hot sun for about 1 to 2 hours, this is why it is delivered in black bottles. this will force the air out of the fluid. if you don't do this you will never get a hard brake petal no matter how much you bleed the system. also NEVER use silicone brake fluid in a anti-lock bracking system.
This is interesting. I never heard about placing a bottle of brake fluid in the sun for a couple hours. My son flushed the brake fluid on our '01 Dakota at tech school. It has never been the same since. Brakes fine at highway and even lower speeds; however at very low speeds the front brakes seem to grab much harder than they should. My company truck is identical and it brakes totally different. I might be reaching for straws but maybe they used silicone fluid...
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Re: Replacing Dot 3 Brake Fluid with Dot 5
[Re: 73cudaproject]
#89159
07/16/08 11:21 PM
07/16/08 11:21 PM
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Joined: Feb 2003
Posts: 4,204 Fort Worth, TX
Clair_Davis
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I've never let the fluid sit in the sun to remove bubbles before, I just pour it slowly in to the MC and try to not create any excessive bubbles while bleeding. I've never really had a problem with a spongy pedal at all, either. That may have something to do with the 1-1/32" MC more than anything, but I did notice an improvement in pedal feel when I swapped the front hoses to braided stainless units. As for compatibility, I used to keep a plastic Coke bottle in my garage that was half full of a 50:50 mix of used DOT3 and DOT5 fluids. Periodically, I would shake up the bottle and see if anything would ever happen to the mix. The only thing that really happened was that the two fluids would be mixed up in to a frothy mix for a while, but within a couple minutes you could see a distinct layer between the two. After an hour or so, there were no visible bubbles in the silicone fluid, and both were nearly clear again. Never saw any trace of goo, sludge, crud, or corruption in the bottle. DOT regulations require that the brake fluids be compatible. The following is an excerpt from the 49th Code of Federal Regulations, Section 571, Federal Motor Vehicle Safety Standards, Subsection 6.10 Quote:
S6.10 Compatibility. The compatibility of a brake fluid with other brake fluids shall be evaluated by running one test sample according to the following procedure. S6.10.1 Summary of the procedure. Brake fluid is mixed with an equal volume of SAE RM-66-04 Compatibility Fluid, then tested in the same way as for water tolerance (S6.9) except that the bubble flow time is not measured. This test is an indication of the compatibility of the test fluid with other motor vehicle brake fluids at both high and low temperatures. S6.10.2 Apparatus and materials. (a) Centrifuge tube. See S7.5.1(a). (b) Centrifuge. See S7.5.1(b). (c) Cold Chamber. See S6.7.2(b) (d) Oven. See S6.9.2(d) (e) SAE RM-66-04 Compatibility Fluid. As described in appendix B of SAE Standard J1703 JAN 1995 ``Motor Vehicle Brake Fluid.'' (SAE RM-66-03 Compatibility Fluid as described in appendix A of SAE Standard J1703 NOV83, ``Motor Vehicle Brake Fluid,'' November 1983, may be used in place of SAE RM-66-04 until January 1, 1995.) S6.10.3 Procedure. (a) At low temperature. Mix 50 [plusmn]0.5 mL of brake fluid with 50 [plusmn]0.5 mL of SAE RM-66-04 Compatibility Fluid. Pour this mixture into a centrifuge tube and stopper with a clean dry cork. Place tube in the cold chamber maintained at minus 40[deg] [plusmn]2 [deg]C. (minus 40[deg] [plusmn]4 [deg]F). After 24 [plusmn]2 hours, remove tube, quickly wipe with a clean lint-free cloth saturated with ethanol (isopropanol when testing DOT 5 fluids) or acetone. Examine the test specimen for evidence of slugging, sedimentation, or crystallization. Test fluids, except DOT 5 SBBF, shall be examined for stratification.
Obviously, mixing fluids diminishes the benefit the higher-rated fluid.
Clair
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