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  #1  
Old 02-26-2012, 03:25 AM
cudabob496 cudabob496 is offline
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Default Brake Fluid

Its been about 10 years. Should I replace all the brake fluid in my Cuda, and if so, what kind should I use?
ie DOT3, or 4, or 5?, etc
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Old 02-26-2012, 02:58 PM
dodger1 dodger1 is offline
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My choice would be silicone fluid (DOT5) Just flush the old stuff out as best you can. Never mind the idea that 5 is not compatible with 3 or 4, or that it'll harm some rubber components, it cannot in order to meet federal standards. Advantage to silicon fluid is it will not absorb water, thereby minimising corrosion . Condensation can still collect, but it will settle out at low points only. I have used it in the Mirada for about 5 years now, as well as my old Suzuki GS850 front brakes. Quite happy with it. Yes, the pedal is just as firm as it was with DOT3.
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Old 02-26-2012, 04:41 PM
Skwerly Skwerly is offline
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I'd stick with the DOT 3, myself; it's what the system was intended for.
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Old 02-26-2012, 05:25 PM
dodger1 dodger1 is offline
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Quote:
Originally Posted by Skwerly View Post
I'd stick with the DOT 3, myself; it's what the system was intended for.
So was the Mirada. However, after having to change out all the steel lines, and doing a lot of research on the 3 types of fluid, I went with silicone. More info from Mopar Action tech site here: http://www.moparaction.com/Tech/ques..._IMPLANTS.html . I believe H.D. as well as others use it as O.E.M., and yes their brake systems may have been optimised for DOT5. Just sayin'
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Old 02-27-2012, 01:21 PM
340_GTS 340_GTS is offline
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If you read this article, you will probably not want to put DOT 5 in a vehicle that does not require it. Seems like it is good for race cars, but not much else. http://www.motorcycleproject.com/mot...rakefluid.html
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Old 02-27-2012, 07:18 PM
440roadrunner 440roadrunner is offline
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In all the cars I've had, some fairly old, I've never had much problems with DOT 3. THAT is what I'd use.

Side story. You guys remember the IHC Scouts? Those darn things used an English Girling clutch hydraulic system, and MANY guys made the mistake of putting US fluid into them, which ruined the rubbers. 'Course, if you bought A Raybestos or Wagner kit, they came with synthetic cups, so after that you didn't HAVE to use Girling fluid.
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Old 02-27-2012, 10:08 PM
dodger1 dodger1 is offline
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One thing wrong with the motorcycle project quote: Liquids are NOT compressible. (Extreme pressures/temps excepted) Any liquid. Glycol or silicone are the same in that respect. Which causes me to doubt the author's info in general. (http://wiki.answers.com/Q/Are_liquids_compressible)
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Old 02-29-2012, 07:07 AM
cudabob496 cudabob496 is offline
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I think liquids are compressible. As you compress them, the pressure goes up,and the volume goes down. They are not as compressible as gases, but more compressible than solids.

http://hyperphysics.phy-astr.gsu.edu.../compress.html
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Old 02-29-2012, 08:05 AM
340_GTS 340_GTS is offline
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And I think the writer was (at one point) talking about how the DOT-5 stuff can easily get aerated with microscopic bubbles. Then it would be compressible.
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Old 02-29-2012, 08:11 AM
chirorod chirorod is offline
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The motorcycle link has lots of problems. In brake systems, liquids are, for practical purposes, not compressible. It is not the water content of brake fluid that might make it compressible; it is air content, which would result from leaks. It is the non-compressibility of liquids, including water, that makes hydraulic systems possible. Water could be used as a hydraulic fluid, but boiling point and corrosion don't allow its use in brakes. Water content in brake fluid is a major problem for two main reasons. One is the corrosion that occurs. Two is the lowering of the boiling point of the brake fluid. Brake systems get very hot. For racing applications and other hard driving and long mountain descents, the fluid boiling point is a critical matter. As the fluid boils, it becomes gaseous and more compressible and doesn't push the caliper or cylinder pistons out, making for decreased or no braking. The current brake fluids available are pretty good as far as boiling point and resistance to corrosion aspects. So, go ahead and flush out the system and use dot 4. It won't harm the seals. And you may have better safety from a higher boiling point (which would be handy around the house, because my wife has a low boiling point). However, an old system might already have degenerating seals, so it might be time to revitalize the system by rebuilding calipers and cylinders.
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Old 02-29-2012, 01:10 PM
Skwerly Skwerly is offline
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you can put pressure on brake fluid, but it won't compress. that's why it works well as brake fluid. air bubbles won't make the brake fluid compress, it just seems like it; the air bubbles are compressing, not the liquid.
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Old 02-29-2012, 04:10 PM
dodger1 dodger1 is offline
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Re: boiling point, isn't the latest Glycol fluid (DOT5.5) equal to silicon fluid with the highest boiling point?
Also, I never had an issue with a soft pedal after switching to silicon fluid. I did have an initial bleeding problem, though. I had replaced almost all steel lines, the rear wheel cylinders (badly corroded) and put a kit in the master. I failed to properly bench-bleed the master (1st time I'd done one in years) before installing it and had a hell of a time bleeding the system. It eventually "bled" itself and the brakes are just fine now. Especially after swapping in the 11.75" rotors from a 78 Cordoba.
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Old 03-05-2012, 07:23 AM
cudabob496 cudabob496 is offline
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Ok gang, I pulled the lid off the master cylinder, hooked up a tube to the bleeder valve on the rear left wheel, let the bleeder valve soak with liquid wrench on it for about 1 hour, then turned the valve slightly (after giving it a few wacks), and had the tube running to the bottom of a 1 quart empty plastic water bottle. I then pumped the brakes slowly, refilling the master cyclinder about every 10 brake pumps, and got some old nasty dark brake fluid out of the rear right bleeder valve (about 12 ounces). You can do this on your own, as long as the bottom of the plastic tube inside the plastic bottle is covered with brake fluid, so air does not go back into your system after you stop pumping the brake pedal, and before you close the bleeder valve. I used Wilwood racing DOT3 fluid from Summit, and used almost three 12 ounce bottles for both back wheels. Once I got about 12 ounces out, I closed the bleeder valve, and the brake pedal was nice and firm. Repeated on the rear right wheel. Did not need to use my brake bleeder hand held vacuum pump to bleed brakes. Just make sure the plastic tube is snug on the bleeder valve, and that the end of the tube is covered in brake fluid inside the plastic bottle. I imagine that some of that brake fluid I got out may have been 40 years old, unless someone had flushed the system before I got the car 20 years ago!
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Old 03-05-2012, 02:06 PM
chirorod chirorod is offline
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Unfortunately, vintage doesn't confer value on brake fluid as it does on wine.
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Old 03-06-2012, 05:07 AM
cudabob496 cudabob496 is offline
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Quote:
Originally Posted by chirorod View Post
Unfortunately, vintage doesn't confer value on brake fluid as it does on wine.
And the brake fluid doesn't taste as good.

car guy extra video:

http://www.youtube.com/watch?v=_MKyZ...eature=related
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