Hello John and Mike,
>
>On Wed, 19 Mar 1997, John Cowan wrote:
>
>> The disk brakes on my '60 TR-3A do not release after they are applied
>> (with the car up on a rack). Mechanic says that the silicone brake fluid
>> used by former mechanic has softened O rings in brake mechanism so that
>> they no longer retract the pads when the brake pedal is released.
>> Any thoughts or similar experiences?
>> Thanks.
>> John Cowan
To which Mike responded :
>
>Hi John, I have a couple of comments on your question/problem:
>
>Very often, the cause of this problem is a bad brake hose. The bad hose
>is often not apparent from a visual inspection however. As a hose ages,
>it can break down on the inside and swell shut. In effect, it forms a
>"check valve" that will allow fluid to pass when you press the brake pedal
>(extremely high pressure involved here), but not allow fluid to flow the
>other way when the pedal is released (the disk brakes have no return
>spring or anything to force the fluid back). The result is dragging
>brakes. If the hoses on your car have not been replaced in the last 20-30
>years, I think this is a likely source of your problem. Incidentally, the
.....and I just want to second Mike's opinion, I've had multiple brake
hose failures on various vehicles, and they always acted just as Mike
described...and the two front hoses on my '80 Ford F-100 pickup both
failed at about 6 or 7 years old, so unless you know that your hoses
are just a few years old, I'd say they're most likely the problem.
>swelling inside the hose can occur regardless of the type of brake fluid
>you use, which brings me to my second comment.
>
>Your mechanic's assessment of the situation may well be true (swelling of
>seals), but let me make a case against it :-) Early silicone fluid
>formulations did have problems with swelling rubber seals, but these
>problems have been worked out and you shouldn't encounter this with fluid
>produced in the last 10 years or so. Below I've attached a short article
>I wrote a few years back to the SOL group about DOT 5. Maybe it will help
>in your diagnosis of the problem.
>
>Good luck
>Mike Burdick
>Omaha NE.
>'70 Spit, 5 years on silicone fluid with no problems.
>
...Since I have no experience with silicone brake fluid, no comment there.
Tom Tweed
SW Ohio
'72 TRident 750cc basket case
[DOT 5 info snipped]
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