Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Silicone vs. ordinary brake fluid

Also ran it with good results in 105 series Alfa Romeo racecars -more Gorilla than Giulia ....

waikiore do you have pictures from that time with the alfa that you can share? we have a 1970 Giulia 1600 super that my wife drives. I would be very curious.

Still confused but a higher level.... Has anybody actually experienced these detrimental effects of silicone? Of course they could be hidden down there somewhere, waitilng to surface. I do take notice of the air bubbles in a TR3 and the fluffy concrete on a Harley, but that is two... As an experiment, I have mixed silicone and glycol 50/50 in a glass. They separate in two layers when left alone, behaves like oil and water, but no gel. When agitated (shaken, not stirred) they mix, but still no gel. If this is transferable to the brake system I do not know, but FWIW that is what happens on my shelf. As for NATO, I find it surprising that NATO vehicles are stuck with something that puts the brake system at risk. It is silicone here in Norway too, can NATO really force the Norwegian military authorities (yes, we are NATO members) to use something that alledgedly has negative effects and may represent a traffic risk? Just wondering.
Finally, let me grab the opportunity to thank Lorne for a comprehensive answer (although I might differ here and there...) and for the splendid source that GoMog is. An obligatory read for every serious mogger!

Robbie ... my comment re the Harley was just regarding how it was viewed in period ...... in fact even back then I flushed it out and changed to DOT3 purely to have the same fluid on all my various vehicles for convenience (no detriment noted by me either when pushing out DOT5 with DOT3 .... just noting how perceptions change.)

The 'fluffy concrete' reference may not travel beyond the UK where we have an issue with a '60s form of aerated concrete in public buildings that was a 'wonder material' that has now turned out to not age well and causing closures and miilions in emergency repairs.


I have no doubt that DOT 5 used appropriately is a perfectly fine brake fluid.

K
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Like anything else.....and a current example being EV's, there are zealots for every new development. How many banged on about Betamax I wonder? My "knowledgeable" friend criticised my choice of an LED TV. "Plasma is the future" he decreed.

Anyway, I will only relate my personal experiences, which are these. I used Dot5.1 in my Roadster for the first few years, changing every two years, but decided to standardise at Dot4 for "the fleet".

In 1990, silicon fluid was a big deal, and zealots were everywhere in classic car circles. My rebuild BV8 had a completely new braking system.......and that meant EVERYTHING. So I had a simple choice to make. I did the research, although the truth is always masked by zealots. I asked around in the clubs & classic car world. The evidence was patchy. Some people had immediate troubles with Silicon fluid, some wouldn't be without it. Without knowing the background details of those who had had trouble, i.e. whether or not they had done a proper flush, there was nothing concrete to go on. It hasn't been widely adopted by manufacturers either, even now, and so in 1990 I went for Dot4 if it was around then, if not Dot3.

It's a personal choice. With regular flushing Dot4 is fine. With Silicon, it may be fine, but I would not fill and forget. But it may not be fine, and that's the gamble I didn't take in 1990.

Slight digression but in the same vein.

Spurred on by this and other related threads, I've just ordered a brake (and clutch) fluid checker to check the moisture content in my systems.

Simple device you just dip it in the reservoir and note the reading. 1 or 2 percent moisture ok but 3 to 4 change the fluid.

However I have a question. Is the fluid in the reservoir indicative of the fluid in the system itself?

My system loses no fluid so in theory little if any reservoir fluid gets into the system, I haven't needed to top up the fluid in the 2 years and 8000 miles since the last change.

So I can understand how the reservoir fluid might absorb some moisture from the air gap and when opening the cap to check the fluid levels but how would moisture get into the main system down stream of the reservoir and therefore how does moisture get absorbed into the fluid?

I know it does absorb moisture and that it should be changed every 2 years but my brain is insisting I find out how and why.

Any thoughts?

General theory Bob is that air (and moisture/condensation) gets in through the seals, especially at the rear wheel cylinders. This is why the rear cylinders get so rusty around the edges.

And the fluid from the rear system is always a lot more contaminated and black than from the front.

Thanks for that Dave, makes sense and I did get rear cylinder seizures on my old 4/4.

So the fluid reservoir moisture check should be a good indicator for the whole system.

Can't wait to play with my new toy.

It would be interesting Bob to bleed some fluid from a rear cylinder and caliper, to compare moisture levels with the M/Cyl.........if you can be arsed.

Very true I had one 4/4 that failed at the rear claipers and have just replaced them on Belle at 10 years and 36k as they were starting to fail. Not helped I suspect by a failed oil seal on N/S axle.