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Hi have a 1955 F100, and on their forum suggests that mineral brake fluid should be used, however I have a Camaro Clip with discs, remote dual circuit brake booster and new rear brake cylinders. I have used the mineral fluid as recommended but the main seal in the master cylinder has now started to leak. Should I have used the synthetic fluid?
 

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WTH is mineral brake fluid ? Never heard it referred to in those terms ?? If you're contemplating switching to DOT5 ( silicone) , you're system will have to be flushed thoroughly ( I've never figured out how to do that ?) If not I guess you end up with some gelled guck ? I'd be surprised if the seal leak had anything to do with the fluid type .....

I edited this , sorry , my brain said silicone , my fingers wrote synthetic ...
 

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Once ya use dot 5 you will not even consider the old paint eating dot 3 or 4 again. No water/moisture absorbed but it not comparable with the old dot 3/4.
For any car that sits a lot as in all winter dot 5 is my preference.

Clean up is easy with Lysol as it is a silicone base.
 

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Once ya use dot 5 you will not even consider the old paint eating dot 3 or 4 again. No water/moisture absorbed but it not comparable with the old dot 3/4.
For any car that sits a lot as in all winter dot 5 is my preference.

Clean up is easy with Lysol as it is a silicone base.
I heard that 5.1 is better than 5 as it will absorb moisture (something you WANT it to do) unlike 5 which will not and leads to expensive brake system repairs due to moisture contamination.
 

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I heard that 5.1 is better than 5 as it will absorb moisture (something you WANT it to do) unlike 5 which will not and leads to expensive brake system repairs due to moisture contamination.
I think not. Most high end brake systems use stainless and aluminum vs the cheap cast iron OEM systems. Most guys owning street rod of some kind have upgraded brakes. Dot 5 is silicone base and not compatible with water. Moisture in the system says something is not air tight and letting in. Why would you want the brake fluid absorb water it is compressible and inhibits braking? The whole idea of brake fluid is it is hardly compressible at all.

Dot 3 does give a slightly harder pedal. Dot 5 is thicker and not quite as hard a pedal comparing like systems. But this amount of difference is so small as to make no difference to the driver. Brake pad friction differences would be a much greater feel to a driver.
 

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DOT 5.1 is totally different than DOT 5 brake fluid. Think of 5.1 as a glycol based DOT 4 fluid that meets DOT 5 silicone-based fluid standards. The 5.1 fluids are used primarily in vehicles equipped with ABS brake systems.

Unlike glycol based DOT 3,4 and 5.1 fluids, DOT 5 silicone brake fluid will not absorb water from the atmosphere or act like a paint remover. Silicone has very high dry and wet boiling points. It is also more compressible and can absorb more air than a conventional brake fluid.

DOT 5 does have its applications. If you own an extremely rare car that has expensive or original paint, DOT 5 is the fluid for you because it will not eat away the paint if spilled. But, if you use DOT 5, you are almost required to bleed the brakes before you go for a spin. Why? DOT 5 is lighter than water. Any moisture will pool at the lowest point which is typically the calipers or wheel cylinders. Many classic cars have been lost after the owner decided to shake loose the cobwebs before bleeding the brakes.
 

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I heard that 5.1 is better than 5 as it will absorb moisture (something you WANT it to do) unlike 5 which will not and leads to expensive brake system repairs due to moisture contamination.
Ive had DOT 5 in my T for 20 years , flushed it once at 8 years , stuff looked like new , haven't messed with it since !
 

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I run dot 3 where it is/was recommended.

The main reason is it is cheap. 5 and 5.1 are 2 to 3 times the cost.

I buy the cheap gm single piston (2.5 bore) calipers which are hit and miss on quality.

The boots on these go bad over time and then your filling 1/4 to the entire system.

I also replace rubber lines every 60k/5 years yet another fill.

These are cheap maintance things. But when the fluid is $80 vs $25 you may be tempted to keep more of the old 5/5.1 fluid vs flushing the entire system.
 

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I've never flushed brake fluid on anything other than race cars
When replacing the wheel cylinders on my 2000 Express 3500, the 20+ year old fluid was rusty as all hell so I flushed the system the best I could. Had to be a lot of water in that old fluid, no wonder the wheel cylinders were rusty and leaking. I'll try to flush it again in 5 years.
 

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When replacing the wheel cylinders on my 2000 Express 3500, the 20+ year old fluid was rusty as all hell so I flushed the system the best I could. Had to be a lot of water in that old fluid, no wonder the wheel cylinders were rusty and leaking. I'll try to flush it again in 5 years.
99 to lets say 08 trucks and vans had cheap lines from the factory.

The 2500hd and up frames do not rot out like the 1500 ones do, transmission is better, and a couple other goodies that keep them out of the junkyard surrounded by 1500's. But the lines on all of these years are still junk.

You might want to consider replacing your lines and rubber next time you do pads.
 

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DOT 5 will not absorb water, but holds air in micro bubbles, the reason it typically has a bit spongy pedal. And since water can make it in there by the vented master cylinder, once it gets in there and sinks to the lowest point since it is denser than DOT 5 fluid, and corrodes in the one area.

By the way, glycol is a reformed mineral oil product.
 

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DOT 5 will not absorb water, but holds air in micro bubbles, the reason it typically has a bit spongy pedal. And since water can make it in there by the vented master cylinder, once it gets in there and sinks to the lowest point since it is denser than DOT 5 fluid, and corrodes in the one area.

By the way, glycol is a reformed mineral oil product.
Do not shake it up. Air is lighter than dot 5 by a huge amount and will rise to the surface given time. Sorry but argument does not justify no dot 5. Typical classics have air tight cap and seal master cylinder and these are the target use for dot 5. Modern anti lock systems are not viable candidates for dot 5 as they are not designed for it.
 
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