...to use in a restoration where all of the brake parts are brand new. Should I stick to the old type which needs regular changing, or go for the newer silicon based fluid. 1972 Type 1 front disc rear drum.
TIA
Tony
Silicone based takes more pressure on the pedal to compress the fluid --- hence longer stops! Stick to the old stuff.
What? That's crazy. You can't compress any of the brake fluids.
Anywho, unless seals have changed, the ACVW should use DOT 4.
Either will work. Your other brake parts will last longer if you switch to the silicone, but you have to flush it thru vigorously in order to remove as much of the old stuff as possible.
There is some chance that the brake light switches won't last long with the silicone, but I'm not convinced that this is the fault of the silicone rather than the poor quality of current switches.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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I've used silicone fluid in my VW for 25 years with no complaints. I used to have to buy new wheel cylinders when water, which is attracted by the old style ethylene glycol based brake fluid, corroded the metal and leaked fluid past the seals. Since I switched, I've never had to buy replacement wheel cylinders.
Randall
So thats one reply that says it requires more effort, a couple for the silicon, and one for the old stuff it was designed for.
Question - if silicon fluid was widely available in 1972 would VW have specified it.
Comment - I did stress it was a completely new braking systen - every hydraulic part has been replaced.
Any more wisdom - I am inclining to Jim Adney's 25 year experience and my gut feel that I'd give the silicon a try unless there was a convincing argument to the contrary.
TIA
Tony
nope...manufacturers don't spec it now for your run of the mill dialy driver...
This link explains the pros and cons of glycol based and silicone based fluids.
Thanks, and I did you a disservice - its you that has the 25 years experience.
Tony
Not true, and I think even Wolfgang would agree that this doesn't make sense. The PRESSURE is the same in all parts of a hydraulic system, this is the fundamental principle of hydraulics. So more pressure in the master cylinder automatically translates into more pressure elsewhere, like in the wheel cylinders. More pressure in the wheel cylinders would mean more braking (assuming the same brake shoe material.)
There IS the possibility of more pedal TRAVEL with silicone, if the stuff is not installed properly and allowed to absorb air, but this is different from pressure.
I've used it exclusively in all my VWs since 1978 and my experience is that it actually reduces pedal force (and consequent system pressure) simply because it is a much better lubricant between the seals and the wall in the MC and wheel cylinders. IOW, it is slippery, and this means that less pedal force is consumed in overcoming brake component friction. The reduction in MC friction has made a HUGE reduction in the wear that my brake component seals sustain in use.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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The "rubber" seals used in all brake systems since about 1962 are all compatable with DOT 3, 4, and 5 brake fluids.
Dot 4 has a higher dry boiling point than Dot 3, but I've had bad luck with Girling LMA Dot 4. It just didn't lubricate well and my seals all wore out in a very few years.
Both Dot 3 and 4 are hydroscopic, which means that they will absorb water out of the air, bringing their boiling points slowly downward. This means that they should both be flushed with clean, dry fluid every few years.
The boiling point of DoT 5 is higher than either DOT 3 or 4, plus it is non-hydroscopic, so it does not need to be periodically flushed.
Yes, I know that no one out there actually flushes their brake fluid. Instead you just wait for something to fail and then replace it. Flushing is a lot easier and cheaper. Replacement with DoT 5 is expenive up front, but if you actually keep your car for a long time it's well worth it, because of all the trouble and replacement parts you'll save yourself.
If you're interested in DoT 5 silicone brake fluid, I have a FAQ that I'd be happy to forward to anyone who emails me directly.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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Nice to hear from another convert. Your experience is the same as mine.
I used to have to rebuild MCs about every 4 years and calipers every 2 years. When I got to about 4 ACVWs this got to be quite a work load. I switched to DoT 5 in 1978 and have never regretted it.
Since then I've had to rebuild very few of my brake components. My daily driver developed a bit of a leak in the MC a couple of years ago. That car was a '73 that I bought in '90. I put in Dot 5 and rebuilt the calipers and rear cylinders at that time, but I didn't touch the (original) MC at that time.
When I recently removed the MC to fix the leak, it turned out that the MC had developed some rust in the rear opening. The rust was holding the seal slightly away from the MC wall, so the fluid could leak by slowly. All I did was hone that rust down smooth, and clean around the opening. I inspected the seals, and they were still fine, pliable and with good sealing edges. I put those (original) seals back in, and they've continued to serve well for 2 more years. I don't expect any trouble from them unless the rust builds up again.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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They could not have done so. The fluid was available even before that, but it did not get DOT approval until the late '70s. It was still installed by some individuals, however, but some changes in the formulation were made between '71, when a friend of mine installed it in his Super Beetle, and '77 when I finally got serious about looking for it. (It WAS hard to find in those years.)
We don't find it installed by OEMs because it is more expensive than the polyglycol fluids. GM and Ford could not tolerate the extra $3 per car that it would cost.
Harley and some other small makers DO install it at the factory, however.
You may note that all the Bentley manuals for water cooled VWs specifically state that silicone brake fluid should NOT be used in those cars. I can not see any reason why this should be true. The components in those cars are all the same as in ours. Dow-Corning, in their testing, has installed silicone in hundreds of those cars, and I've done it in dozens. I've never had a problem that was related to the fluid itself in any car that I've put DoT 5 in.
There IS a legitimate question about whether it is appropriate for use in modern cars with ABS systems. The automakers don't recommend it, and I've not heard anything definitive on this. The concern is whether it is a suitable lubricant for the ABS pump, which apparently has metal to metal sliding surfaces. I don't know anything personally about the inner workings of ABS systems, so I've shied away from installing it there.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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The following link:
of ABS and silicone under "Drawbacks #7".
Randall
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