[DeTomaso] Brake fluid Dot 5

Wed Nov 17 13:16:53 EST 2021

I have to admit I laughed out loud when I read Mike's response about museum cars.  

Larry and Mike are right - Dot 5 lasts forever.  And oh yea, it doesn't strip paint if you spill it anywhere and it doesn't absorb water.  And it doesn't eat away at your bake system seals.  

Background.  I have an XKE with 200K miles on it - 160K of which I put on it.  I rebuilt the brakes when I bought the car - in 1980.  I purged the system using 90% rubbing alcohol, then hooked the system up to the inlet manifold and evacuated it.  So, got rid of all the paint remover.  Filled it with Dot 5.  41 years ago.  And have not had to fiddle with the system since.  Yes, I have replaced pads, and periodically I flush with new fluid.  And no, I don't race the car, but I drive it hard.

The Dot 5 vs Dots 3/4 debate is one that has been around forever.  I have 5 cars full of Dot5.  I suppose it is possible I am truly too insensitive to feel the mushy pedal that folks talk about.  On our Pantera - we upgraded to Wildwood brakes and a brake master cylinder/vacuum booster from Pantera Performance.  And have had no problems with using Dot 5.  Our Daytona coupe - drained out the paint thinner, flushed, evacuated and filled with Dot 5.  No problems.  Ditto Lotus Elise, and Mazda AZ-1.  No problems. 

As in, 41 years in a British car, and haven't had to replace seals.  Doesn't sound like bad news to me.

As often pointed out, your mileage may vary.

Stephen Nelson

-----Original Message-----
From: DeTomaso <detomaso-bounces at server.detomasolist.com> On Behalf Of Larry Stock
Sent: Wednesday, November 17, 2021 9:08 AM
To: MICHAEL DREW <mikeldrew at aol.com>; Rich Hoppe <richbhoppe at gmail.com>
Cc: detomaso at detomasolist.com
Subject: Re: [DeTomaso] Brake fluid Dot 5

I agree with Mike to  point here. DOT 5 is silicone, and once it is switched to DOT 5, just figure that you have switched. As Mike has pointed out it is not easily reversable. It does work just fine for street driving use, you just won't have optimal braking, which on top of the stock Pantera Braking system could use other improvements to help things out, but is just fine for Sunday driving. DOT 5 does not absorb moisture, so your braking components will last a lifetime.
Larry Stock

On 11/17/21, 8:51 AM, "DeTomaso on behalf of MICHAEL DREW via DeTomaso" <detomaso-bounces at server.detomasolist.com on behalf of detomaso at server.detomasolist.com> wrote:

    Rich,

    When it comes to brake fluid you need to pick a lane. DOT5 and DOT3/4 are completely incompatible. 

    DOT5 is intended for museum cars that won’t be driven. It lasts forever and allows the brakes to work and will prevent corrosion. But the brakes won’t work very well and the pedal will be squishy. 

    If you intend to actually drive the car you need DOT4. When 4 and 5 are combined the chemicals react and it turns into a horrible mess. So you can’t just think you can pour DOT4 in the system and bleed the brakes until the DOT5 is all gone. It will
    Completely plug up the brake system. 

    You need to completely drain the whole system of DOT5, then run multiple cans of brake cleaner through the whole system to ensure there is not one drop of DOT5 remaining.  I would remove the supply line from each caliper to the hard lines, open the caliper bleeders fully, and blow a whole can of brake cleaner through each flex hose, into and through the caliper and out the bleeder into a catch bottle. 

    DOT5 is really bad news….

    Mike

    Sent from my iPhone

    > On Nov 17, 2021, at 07:25, Rich Hoppe <richbhoppe at gmail.com> wrote:
    > 
    >    I am restoring my car to original.
    >   So I have the rebuilt original brake calipers on the car.
    >   I wanted to individually bleed the calipers as I connected them.
    >   Then in the next step change the master/booster over to original after
    >   rebuild.
    >   It turns out I currently have Dot 5 fluid in the system.
    >   Can I continue to use Dot 5 in the system?
    >   Or do I need to flush and go to Dot 4?
    >   Thanks
    >   Rich Hoppe
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