Dot-5 ok?

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b5cuda

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Hi all,
I've been running DOT-5 brake fluid in my '69 cuda for a few years without issue ('73 style front discs, rear drums) , but a mechanic friend recently warned me that it's not OK to run synthetic fluid with components that were designed for older style fluids. Has anyone else heard this, or had experience with it? Any idea whether it eats soft parts or...? Thanks,
Bill
 
No, you're ok. What he's probably referring to is that NOWHERE NOHOW NOTIME are you supposed to mix dot 5 with any other type of brake fluid. THAT'S when you run into trouble. Just curious though.......why are you runnin DOT5? You just like spendin money?
 
My entire brake system was new so it seemed like the time to try DOT5... it's not hard on paint if you have a spill, and supposed to be more resistant to taking on moisture and rust. It's been used on cycles and aircraft for years so my friend and I thought we'd try it. I've heard of other guys using it and I've been happy, just don't want any surprise failures at some point so thought I'd ask.
 
dot 5 is fine in there. bleed the system at the start of every year. dot 5 doesn't absorb the moisture like dot 3 does and they say the moisture will collect in the calibers and wheel cyls..
 
i been running DOT 5 in my car for 10 years never touch, it works great
 
The military has used DOT 5 exclusively in all tactical vehicles since the mid 80's. Great stuff. Many myths and wives tales out there. Like any brake fluid it should be replaced every couple years.
 
As long as you replace it every few years your fine. It's not hygroscopic (absorbs water) like the other Dots. What this means is that when water does enter your braking system it is not absorbed and dispersed by the fluid, instead it gathers in spots, usually your calipers. With water sitting there it is much more apt to corrode and deteriorate your break lines, calipers, etc. When you have water sitting in your calipers, it's also closer to a heat source (your brakes). Dot-5 has a boiling point of 500 degrees F, water has a boiling point of 212 degrees F. You're brakes and calipers can easily reach 212 degrees F. Once the water in your line boils, it creates a gas, which is highly compressible (called brake fade). Thus your brake pedal goes all the way to the floor board, and you're still cruising at 65 into an oncoming semi. Also, Dot-5 is a bit more compressible right out of the can than your Dot-3/4. You can develop a spongy break pedal more easily once water enters a Dot-5 system, compared to Dot 3/4.

Dot-5 is a synthetic, its much less harsh on paint if spilled, and easier on your brake system. So as long as you do the maintenance... , and change your fluid (davescuda you scare me!:toothy10:), you're good to go!
 
My entire brake system was new so it seemed like the time to try DOT5... it's not hard on paint if you have a spill, and supposed to be more resistant to taking on moisture and rust. It's been used on cycles and aircraft for years so my friend and I thought we'd try it. I've heard of other guys using it and I've been happy, just don't want any surprise failures at some point so thought I'd ask.

a fellow I bought a dodge truck from put DOT 5 in and meantioned it when I purchased it, what surpised me is that he also told me that the brake lines were the original and he drained the DOT 3 when he bought it new and put the DOT 5 in. I could tell he wasn't lying as the lines still had the wire wraped around it on the master cylinder lines and others seems DOT 5 doesn't rot the lines as bad
 
Thanks for all the input - great site! I've had no issues with DOT5, but if I'm supposed to change either kind of fluid every few years, I wonder if it's worth the extra cost to keep using DOT5. Sounds like performance and reliability are about the same, so other than being easier on paint when spilled, I'm not sure I see enough advantages to justify the extra cost. Guess my next question is if I want to change back, can I just drain the DOT5 and replace with DOT3/4, or does the system need some kind of flush?
 
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