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Old 10-05-2020, 01:40 PM
Chris65LeMans's Avatar
Chris65LeMans Chris65LeMans is offline
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Default DOT 5 brake fluid.

Since I'm basically rebuilding my brakes, I went and bought some Wilwood Dot 5 brake fluid and added it to my system during the bleeding process. (I'm in the middle of that now - I managed to let the master run dry and fill the system with air, so I'll need to bench bleed that and start over.)

The stuff that was/is halfway in there now is the "normal" yellowish liquid. In the absence of any warnings on the bottle, I figured that the heavier DOT 5 fluid would flush the lighter fluid out. (I primed my bleeder bottle with DOT 5, and the yellow stuff flowed right to the top - where it still is a couple of weeks later.)

I've since done some research and found these opinions. (Each of them come from "professionals" and shade tree mechanics alike - I've ranked them in order of severity.)

1. I have ruined my brakes forever and a fiery death is now inevitable.
2. The only way to avoid #1 is to install an entirely new brake system.
3. The only way to avoid #1 is to rebuild my entire braking system - new seals everywhere and new brake lines.
4. The only way to avoid #1 is to bleed the system with de-natured alcohol, and pray for a miracle.
5. Just bleed the system 'til the purple stuff (DOT 5) rather than the yellow stuff is coming out, and let 'er rip.

What do you all think?

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  #2  
Old 10-05-2020, 02:14 PM
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J GLASGO J GLASGO is offline
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Yes. Flush till purple comes out. Have done at least a 100 cars over the years. Silicone fluid does not harm paint, nor absorb moisture. Unlike dot3

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Old 10-05-2020, 03:06 PM
mgarblik mgarblik is offline
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DOT 5 brake fluid is a stand alone fluid, not compatible with some types of rubber in brake systems. If your car was newer and had ABS, yes, most of the system would be ruined because the ABS unit has lots of tiny seals you can't get to that would swell up and get stuck. Without ABS, flush the system with DOT 3,4 or 5.1. Those 3 fluids are all glycol based and compatible. DOT 5 fluid, silicone based, used in a system not designed for it, will cause problems of swollen seals and hoses. Hopefully, you caught it in time and can get it out, or possibly your new brake components are compatible with DOT 5. One way to know would be to take the MC cover rubber seal and soak it in DOT 5. If it's not compatible, it will swell overnight to 1.5-2 times it's normal size. Then you will know.

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Old 10-06-2020, 01:27 AM
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Chris65LeMans Chris65LeMans is offline
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Quote:
Originally Posted by J GLASGO View Post
Yes. Flush till purple comes out. Have done at least a 100 cars over the years. Silicone fluid does not harm paint, nor absorb moisture. Unlike dot3
Thanks! A lot of weird info going around on this.

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  #5  
Old 10-06-2020, 06:10 AM
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It is true your not supposed to use with abs. It has been in several of our own, and customers cars for 30 years.

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Old 10-06-2020, 08:40 PM
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I've been running DOT 5 in my car for years. Never had an issue.

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Old 10-06-2020, 11:18 PM
SR-71 SR-71 is offline
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As far as I know you need to replace all rubber components and flush the metal lines with DOT 5 before reassembly and adding DOT 5 since they are not compatible with DOT 3.

  #8  
Old 10-07-2020, 01:24 AM
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Jack Gifford Jack Gifford is offline
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I used DOT-5 fluid when I built a '64 Ranchero back in 1972- no special rubber parts, etc. My son is still driving it, with no brake work ever needed. Same story with my '59 GMC since 2010.

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Old 10-09-2020, 03:59 PM
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I did mine when it was all new components. I reread your original post. If there was something other than DOT5 in the system I'd flush it. That said, are we talking the silicon DOT 5 or the non-silicon DOT 5.1. No need to flush for 5.1.

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