Putting this simply - you were told lies.
The problem with the seals is in MIXING the two fluids as the compounds used
to make the seal reacts differently to a mixture but can happily live with
EITHER ONE on its own.
Silicone and Synthetic are two different fluids in the braking world and a
Synthetic DOT 4 is NOT miscible with a Silicone DOT 5 as Greg has just found
out. He needs a flush out and will need new seals all the way round. If
the guy in the shop suggested Synthetic knowing that Silicone had been used
before, then perhaps the bill for a new system should be left with him. Or
better still let the shop take it to and pay a garage that will do the job.
('Cause it's odds on it will need a couple of flushes and every seal
replacing. If it were my car, although more expensive, I would find it
easier, quicker and putting my mind at rest by fitting a complete new
Synthetic is NOT a Silicone brake fluid. IMHO Synthetic DOT 4 is miscible
with ordinary DOT 4 and whilst it may live with it, the mix is still not
Mineral brake fluids won't mix with anything else!
You may find
or http://tiny.cc/1qvem is a good read.
Guy R Day
----- Original Message -----
From: "Kitterer Bob"
To: "Spridgets" <firstname.lastname@example.org>
Sent: Saturday, November 06, 2010 2:59 AM
Subject: Re: [Spridgets] M/C bleeding problem
> I have used silicon brake fluid for about 12 years. A little over a year
> ago I replaced all the seals in my brake and slave cylinders and could not
> get any pressure to hold. Then was told that there are no longer any
> seals for use with silicon. Do not know if you are having the same
> Bob Kitterer - witha brakeless bugeye.
> 1960 Austin Healey Sprite (Mk IV in disguise) - in storage
> 1966 Austin Healey Sprite Mk III (Trevor) - still in boxes - in storage
> On Nov 5, 2010, at 12:22 PM, Greg Higgins wrote:
>> I pulled the M/C from my 63 sprite MKII, it was weeping a little bit and
>> dripping onto the rubber floor mat. I took everything apart, put all new
>> rubber seals in then bench bled the M/C. I tried bleeding the system with
>> my 1
>> man bleeder, no luck. I had my wife pump the pedal, with seven pumps I
>> had a
>> hard pedal. Once she took her foot off the pedal, the pressure was gone.
>> I took everything apart again, I figured I may have pooched a rubber seal
>> I put the M/C back together. I installed another new rebuild kit, did
>> everything again as mentioned, I still have the same problem.
>> Anyone have any ideas? I have never had a problem bleeding the M/C with
>> car. The only thing different, I went from using synthetic dot 5 to
>> dot 4?
>> I was looking at the M/C diagram in my shop manual, it show a rubber
>> washer called a valve washer that goes into the bore first, mine has
>> never had
>> one and has always worked.
>> I'm going to try a 3rd time, will put the value washer in and see what
>> happens, failing that , I'll throw a match to the bastard.
>> Thanks for any info
>> Greg Higgins 63sprite
Suggested annual donation $12.75