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Thread: Changing Brake Fluid & Brake Pressure Switch

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    Changing Brake Fluid & Brake Pressure Switch

    Can anyone give advice on which brake fluid to use in a BJ7. Also I have to change the pressure switch for the brake that controls the brake lights and I was wondering if anyone uses any type of thread sealant?

    Thanks

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    Jedi Warrior BJ8Healeys's Avatar
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    Re: Changing Brake Fluid & Brake Pressure Switch

    Hi, Peter -

    Which brake fluid to use is a hotly-contested subject in the Healey world and everyone has their own opinion. Some people swear that the only fluid to use is DOT 3, as original. I switched from DOT 3 to DOT 5 (silicone) in my BJ8 in 1989 when the car arrived home after a fresh paint job. Having spilled my share of DOT 3 on paint in the past, my primary purpose in changing to silicone was to avoid damage to the paint. For cars that are not driven frequently and spend a lot of time resting in the garage, another advantage of silicone is that it does not absorb moisture from the atmosphere and result in rusting of the system components. If you don't mind fluid spillage or flushing your system regularly, DOT 3 is fine.

    I always use Teflon tape on threaded connections, if not for sealing then to prevent seizing of the threads when it comes time to separate the connection again. When I used a stock pressure switch in my brake system, I put Teflon tape on the threads of the switch. However, the pressure switches available today don't seem to last very long, so I changed to a mechanical switch instead of the pressure switch.
    Steve Byers
    HBJ8L/36666
    BJ8 Registry
    Havelock, NC

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    Re: Changing Brake Fluid & Brake Pressure Switch

    BRAKE FLUID
    The great brake fluid debates have raged since before the first internet was invented. For almost 30 years I used and was satisfied with DOT 3 in my Healey. Only after a full brake system rebuild did I change to DOT 5. My choice for Silicon was based upon my much-reduced use of my Healey and its increase in hibernation time.

    Since DOT 5 is not subject to absorbing water vapor, internal water-caused corrosion brake system internals are much less subject to corrosive deterioration. After a 24 year period of no-maintenance installation, a mysterious loss of a relatively small amount of fluid with no deterioration in brakeing, and a 30% discount in brake parts from Moss, I decided to rebuild all brake components. When examining each component during tare-down, I found ALL components to be in very close to pristine condition with no observable requirement for rebuild. (The fluid loss was finally found this week coming from the brake master cylinder where the seal would expand and seal when activated and seep slightly on contraction.)

    My recommendation is for Silicon DOT 5 for Summertime Healeys an DOT 3,4, or 5.1 if you have used these fluids previously and are not rebuilding all components or you have no problem doing a full flush every 2 years. Last, the price of Silicon DOT 5 is much more expensive than DOT 3,4,5.1 and I recently purchased a pint at NAPA for $17 and a quart from Amazon for $14 + $13 shipping. Considering my present age and the longevity of my past rebuild with DOT 5, I see my brake system effort as my last.

    BRAKE SWITCH
    After replacing my original pressure brake switch after 30 years and then 3 Moss switches within the next 6 years, I decided to install an electric brake switch in parallel. Scavenged from a salvage yard, my electrical switch was mounted on the plenum under the dash and activated by the foot peddle arm. I suggest changing to an electrical brake switch as its response and maintenance is far superior to the Healey’s original pressure switch.

    Hope this helps,
    Ray (64BJ8P1)

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    Re: Changing Brake Fluid & Brake Pressure Switch

    More details about my change to silicone fluid and a mechanical brake switch:
    As stated before, I made the change to silicone in Apr 89 after draining the DOT 3 and flushing the system with rubbing alcohol. I rebuilt the clutch slave and master cylinders before refilling with silicone. Found RH rear brake cylinder leaking in May 92. Against all conventional wisdom, I honed the cylinder and installed a repair kit. Brake master began leaking in Sep 92. Against all conventional wisdom, I honed the cylinder and installed a repair kit. Replaced the clutch slave in Apr 03 along with the hose since someone gave me a new cylinder. No maintenance actions on the brake or clutch hydraulic system since then, other than inspections. I have put 97,326 miles on the car since conversion to silicone, so it works reasonably well for me. I probably should have but have not flushed the silicone since initial installation.

    I replaced the hydraulic pressure switch (which has to remain in place to seal the union it is screwed into) with an adjustable mechanical switch from Watson's Street Works, Bozrah, CT. It was expensive for a switch, at $22 plus shipping, but is well made and I have had no problems with my brake lights not working since I installed it and got it properly adjusted. I went through two Moss pressure switches in short order before changing to the mechanical switch. Watson's opinion is that the pressure switch contacts do not "wipe" each other and build up oxidation. The mechanical switch contacts do wipe and so keep themselves clean. Of course, build quality also has something to do with longevity.
    Steve Byers
    HBJ8L/36666
    BJ8 Registry
    Havelock, NC

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    Yoda Randy Forbes's Avatar
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    Re: Changing Brake Fluid & Brake Pressure Switch

    Brake fluid:



    Using Teflon tape on industrial hydraulic tube connections is a no-no, and I'll just leave it at that...

    This is the brake light pressure switch on the last BJ8 I worked on; please note the copper sealing washer seated on the mating taper surfaces. I expect getting a correct replacement is nearly impossible, so if yours is still fitted with one, DON'T LOSE IT! A copper sealing ring is easily annealed, lending itself to a lifetime of re-installations, if need be.













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    Re: Changing Brake Fluid & Brake Pressure Switch

    Yes, Randy, I know <span style="text-decoration: underline">industrial</span> hydraulic rules frown on Teflon tape. But the local Byers code has no problem with it. I've never had a taped joint fail on me, nor rounded off the nut of a previously-taped joint in a fruitless effort to get it apart. I have, however, destroyed nuts trying to get apart non-taped joints.
    Steve Byers
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    BJ8 Registry
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    Re: Changing Brake Fluid & Brake Pressure Switch

    Hi Steve,
    The teflon joint won't fail because the seal is at the flare, not on the threads. The problem with teflon is when the tape gets into the system and blocks something.

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    Re: Changing Brake Fluid & Brake Pressure Switch

    Right you are, Greg. I use the tape on all threaded joints, flared or not, and not so much for sealing properties but for anti-seize properties. For joints that are broken frequently, such as the oil drain plug, the gearbox and overdrive drain plugs, and the rear axle oil fill plug, I always make sure that any residue left in the male and female threads is removed before re-sealing the joint. Using Teflon tape is just the way I prefer to do it and have done it for 30 years, and it works for me.
    Steve Byers
    HBJ8L/36666
    BJ8 Registry
    Havelock, NC

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    Re: Changing Brake Fluid & Brake Pressure Switch

    I bought a set of non-Girling master cylinders from Moss (probably a mistake) but the instructions that came with them said the warranty is void if silicone fluid is used. Why would this be?

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    Re: Changing Brake Fluid & Brake Pressure Switch

    Quote Originally Posted by Richard Dickinson
    I bought a set of non-Girling master cylinders from Moss (probably a mistake) but the instructions that came with them said the warranty is void if silicone fluid is used. Why would this be?
    The seals may not be compatible with silicone fluid.
    Steve Byers
    HBJ8L/36666
    BJ8 Registry
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    Re: Changing Brake Fluid & Brake Pressure Switch

    Quote Originally Posted by Richard Dickinson
    I bought a set of non-Girling master cylinders from Moss (probably a mistake) but the instructions that came with them said the warranty is void if silicone fluid is used. Why would this be?

    Beats me. I bought a clutch M/C with similar warning and installed it, bled, topped up with silicone fluid and went on a 4,000 mile road trip.

    Have heard credible stories of people having trouble with initial install of DoT 5, but if the install goes OK people seem to do fine for many miles.

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    Re: Changing Brake Fluid & Brake Pressure Switch

    Like Randy said, so not lose that copper washer as you will not be able to find a replacement. I tried everything on my BN6 when I had to replace the brake light switch and could never get it the new one to seal properly. Ended up going with a mechanical switch from Watson as Steve Byer mentioned. That worked great and put the old switch back to close up the hydraulic circuit.
    Regards,
    Mike
    Mike Lewis, 1956 Austin Healey 100M - Registry Confirmed

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    Re: Changing Brake Fluid & Brake Pressure Switch

    Steve,
    Do you have photos of your switch install?
    Thanks
    Bob

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    Re: Changing Brake Fluid & Brake Pressure Switch

    DOT 5 has to be compatible with the seals or it wouldn't be certified by the DOT - there is info on this online.

    I have a successful install of it via the brute-force method. All new rubber in all my calipers as well as flushing out all my lines and new Moss clutch master and slave and new Fiat dual master cyl. Calipers and lines were flushed with a couple of cans of brake system cleaner, then blown out with compressed air. I assembly-lubed the calipers with Dow-Corning Silicone O-Ring & Valve Grease. I used a modified version of Randy's recirculating bleeder tube to "bench bleed" the master cyl in situ.

    IMO the problems come when people convert existing systems keeping the DOT 4 rubber parts and maybe not cleaning things out too well.

    It's great to never again have ruined paint.
    Steve Gerow
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    Re: Changing Brake Fluid & Brake Pressure Switch

    I always thought that the copper sealing washer was used if either the switch or the "T" was scratched or damaged so it would not seal properly.
    Joe Schlosser
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    Re: Changing Brake Fluid & Brake Pressure Switch

    I used a Watson electrical brake light switch on my since-sold Jaguar MK2. The one I purchased was a difficult application, but it worked well. The guy who bought the car told me that he had done a lot of advanced electrical work on that car, including removing the points from the fuel pump, etc., but had kept the Watson switch I installed. I think Steve G and others have posted switch conversions that are much easier than the one I used, and probably less expensive. The neat thing was that it was a simple thing to convert back to the original switch simply by switching the wires if necessary.
    Owner of a 1960 BN7 with Toyota 5 speed and a '92 Porsche 968 coupe. Former owner '62 Jaguar MK2, MG-TF brought back from military service in Italy 1958, '61 Healey BT7, pre-A Porsche 356, and a Porsche 944.

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    Re: Changing Brake Fluid & Brake Pressure Switch

    I have installed two BJ8 brake pressure switches recently (don't ask why!) and never used the washer shown above. Both have sealed just fine. So maybe the washer isn't always needed, or maybe my system has the washer wedged inside the female fitting. I always thought those types of fittings didn't need washers (like elsewhere in the brake system).

    As an aside (unless I am mistaken), there are two types of brake switches used on our cars. I think (and please correct me if I am wrong), the older cars have a switch with threads like shown here:
    http://mgaguru.com/mgtech/electric/et119a.htm

    And then later cars have longer threads with the tapered tip as Randy shows above. I mistakenly bought the wrong type when I first tried to fix my brake light problem.

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    Re: Changing Brake Fluid & Brake Pressure Switch

    Quote Originally Posted by Randy Forbes View Post
    Brake fluid:



    Using Teflon tape on industrial hydraulic tube connections is a no-no, and I'll just leave it at that...

    This is the brake light pressure switch on the last BJ8 I worked on; please note the copper sealing washer seated on the mating taper surfaces. I expect getting a correct replacement is nearly impossible, so if yours is still fitted with one, DON'T LOSE IT! A copper sealing ring is easily annealed, lending itself to a lifetime of re-installations, if need be.













    The copper seal ring that Randy is referring to is readily available at any good HVAC wholesaler but you will probably need a freindly HVAC tech to buy them for you as most HVAC supply houses will only sell to guys in the trade .
    they are used on 1/4” and other size copper flare fittings where the flare nut attaches to a device of a different material (steel/brass etc) in refrigeration/AC systems.
    they should always be used where dissimilar materials are put together and a high pressure seal is required . Its basically a gasket .
    "If it aint broke ....dont fix it "
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