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dot 5 brake fluid

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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Apr/11/2018 at 8:23am
Already states... Dot5 good for cars that sit a lot since it doesn't absorb water. It will give you a little spongier/softer pedal as it will compress slightly since it can hold air. Doesn't attack paint, so good for show cars or others that don't want that issue.

What hasn't been pointed out -- DOES NOT work well in high heat situations!CART cars (open wheel -- Indy/F1 types) tried using it long ago and started wearing brakes prematurely and even had some lock-ups and brake fires, IIRC. Dot 5 expands with heat! For most, even rally driving, this isn't an issue as it doesn't expand that much. For CART type cars it is because they are hard on the brakes a lot more and for a longer period of time than a typical rally or auto-cross car. I had to stop using it in my motorcycle because the front calipers would lock up on a hot day. Shaded rear caliper wouldn't, out in the open (and black!)  front calipers would lock up on a hot summer day in the parking lot -- had to pop bleeder to ride home after work! After 2-3 times it came back out. Now those calipers used very little fluid to activate, so that was part of the issue. Car calipers use a lot more fluid, plus the calipers are shaded like my rear caliper was. Never heard of a street or auto-cross car running Dot 5 and having an issue, just the open wheelers and motorcycles.

I ran Dot 5 in my Rambler for about three years. After accidentally adding Dot 3 the second time I said "screw it" and drained/flushed the system and went back to Dot 3. Just didn't remember when topping off! First time I put a good bit in. A day or two later left front wheel started dragging and I realized what I'd done. Flush with alcohol, refill. About a year later almost did the same thing. Got just a dash of Dot 3 in when I realized what I was doing! Got a large syringe and sucked the MC out, topped off. Whew, dodged a bullet!! Well, not quite. About a week later one of the fronts started dragging some. @#$#^$# drain and flush. Well, this time going back to Dot 3!!!  Unless you only use Dot 5 or clearly mark the MC cover (I thought about painting the cover yellow or something that would remind me it's different!) it's easy to put the wrong fluid in, and Dot 5 doesn't mix with anything else. The point is I didn't rebuild the system when switching over the first time  to Dot 5 -- just flushed with alcohol -- or going back to Dot 3 -- just flushed all three times. But just a TINY BIT of Dot3/Dot5 mix will ruin your day! I never pressed the brakes that second time -- just maybe an ounce of fluid in the reservoir, then sucked it out within 2-3 minutes. Couldn't have been more than a couple drops that got through and cause enough gel to clog a line.


Edited by farna - Apr/11/2018 at 8:32am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 990V8 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2018 at 10:25am
I use Dot 3 in all my cars. That way there won't be any confusion.
And I do change the fluid every two years. Bleed it out at each corner. Not hard.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote akimmet Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2018 at 12:22pm
To add to the confusion, there is DOT 5.1! DOT 5.1 is not compatible with DOT 5.
DOT 5.1 is a traditional glycol brake fluid compatible with DOT 3 and 4.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2018 at 1:49pm
Originally posted by 990V8 990V8 wrote:

I use Dot 3 in all my cars. That way there won't be any confusion.
And I do change the fluid every two years. Bleed it out at each corner. Not hard.

Ivor

Yup - you can use any of the inexpensive modern tools, some costing less than 20 bucks, or do as I've done on many of my cars - gravity bleed. Open a bleeder, put a hose on it and the other end in a container and let it run until it runs clear. Do that all the way around. You can be off doing other things while it bleeds. 
It's harder on some cars with all the valving, but I was still able to do my 73 for the most part via gravity bleeding. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXTSY Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2018 at 10:17pm
 I believe that you said the car in question is a '69 AMX.

Here is an often overlooked procedural tip- for what it's worth and regardless of what type of fluid you decide to use.
 
It is important to always disconnect the switch wire and remove the center nylon cap on the brake line pressure differential warning light switch BEFORE bleeding the brakes.
This switch is located down low on the passenger side front firewall. Also, take care not to loose the tiny spring or plastic plunger.

 Without this doing this simple step first, the warning light in the dash could be activated and it can be a real PITA to reset. This is all fully explained in the TSM.
 
Good luck with your project.  Bruce




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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2018 at 10:32pm
Removing the switch core is only needed if you use the pump and bleed method. If you use a pressure bleeder or gravity bleeding, no such procedure is necessary.
The reason? It takes, as I recall, about 80 psi DIFFERENCE between the two sides to trip that switch.
With a combo valve like I have, it's SIMPLE to reset it. When you buy them they try to sell you their special tool to hold the shuttle from moving - the catch is that the shuttle can be reset, thus the switch turned off, by opening the other side and applying pedal pressure JUST until the light goes out.
Been there, done that - bled hundreds of systems (including all of my own in the last couple of years) and nary a problem.
I have the tool that you had to use on Ford systems - it's a metal piece you screw in in place of the switch core but haven't used it much. 
Pressure bleeding with a pressure tank, etc. doesn't use enough pressure to trip the switch, and gravity bleeding uses no pressure, and the vacuum pump tools also don't create enough pressure differential to trip the light.

On my 73, I tripped the light but it went out as soon as I opened the front bleeders and applied some pressure. As quick as the light went out again, I let up and closed the system.

I recommend against the pump it up and have a friend open the bleeder method on cars with older cylinders as that forces the cups of the master into territory that's not been used in how long - that's where sludge, dirt, whatever, forms and you can make a working master worthless.
If your master cylinder is old, don't allow the pedal to go down below normal position as it may just end up cutting the cups on dirt and sludge.
Those master cylinders can be nasty if they've been forced into areas they've not been into in a while.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeanbonjeanbon1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2018 at 4:32am
nice comments guys,
 i'll throw in an all new mc, all new rear cyls, new power booster, rebuilted ss sleeved callipers, and new  lines. I'll check the switch and see if it can be cleaned and reused, or call new one. I'm an old timer and will use a friend to push and hold the pedal but first got to get the engine back to life hope next week. 
the contamination was worst then i tought so might be using dot 5 for that summer driven car  

thanks again for good advices , read you all and wish to put my car back on the road this summer. I'll post pics when i'll be allowed 
Regards,Jean
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2018 at 8:02am
Originally posted by billd billd wrote:


Removing the switch core is only needed if you use the pump and bleed method. If you use a pressure bleeder or gravity bleeding, no such procedure is necessary.
The reason? It takes, as I recall, about 80 psi DIFFERENCE between the two sides to trip that switch.
With a combo valve like I have, it's SIMPLE to reset it. When you buy them they try to sell you their special tool to hold the shuttle from moving - the catch is that the shuttle can be reset, thus the switch turned off, by opening the other side and applying pedal pressure JUST until the light goes out.
Been there, done that - bled hundreds of systems (including all of my own in the last couple of years) and nary a problem.
I have the tool that you had to use on Ford systems - it's a metal piece you screw in in place of the switch core but haven't used it much. 
Pressure bleeding with a pressure tank, etc. doesn't use enough pressure to trip the switch, and gravity bleeding uses no pressure, and the vacuum pump tools also don't create enough pressure differential to trip the light.

On my 73, I tripped the light but it went out as soon as I opened the front bleeders and applied some pressure. As quick as the light went out again, I let up and closed the system.

I recommend against the pump it up and have a friend open the bleeder method on cars with older cylinders as that forces the cups of the master into territory that's not been used in how long - that's where sludge, dirt, whatever, forms and you can make a working master worthless.
If your master cylinder is old, don't allow the pedal to go down below normal position as it may just end up cutting the cups on dirt and sludge.
Those master cylinders can be nasty if they've been forced into areas they've not been into in a while.




which is why I dont like certain people to help me bleed brakes. I'm even careful on new master cylinders. I've never had problems myself.
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