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I need to bleed the brakes on my 67 gto. I'm unsure as to what type of brake fluid is already in the system. What is the best way to go?? DOT 3,4,5???
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Dot 5 is silicone fluid, won't hurt paint so is preferred by trailer queen folks but it does have driveability issues. Dot 4 is very good, high temp fluid, and you can never go wrong with a quality Dot 3. With both Dot 3 and 4, they will absorb water from the air (humidity) and go bad. Best to buy a number of small containers for that reason rather than the large ones.
 

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No corrosive DOT3 here, been there, done that, suffered the consequences. Nearly every Pontiac I work on has had new CNC bent lines or hand bent lines installed, & yes we run DOT 5. Besides leaking brake fluid wiping out brake booster plating & underhood detailing, Ive found over the years, the average Pontiac guy will next to NEVER flush what was at one time, fresh DOT3 fluid from their Pontiac's brake lines & replace it with fresh DOT3. Same average Pontiac guy will b!tch & moan about how bad the late '70's-early 80's rear disc calipers were, I've run several such setups with no problem. Neglect to proper fluid maintainence is what builds up corrosion & causes problems.
 

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All new brake system including lines/Hoses on the '66 in '95 using DOT 3.
Purged the system a few years later and started using DOT 5.
NEVER any Issues and ALWAYS Driven.
IMHO the use of DOT 4 &/or 5 WILL likely end up causing issues if you don't maintain/Drive the car.
They become very problematic when idle for long periods of time which most classics do.
To each their own but DOT 5 has not been an issue.
 
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