I read that Silicon/Dot 5 could be fatal to an engine if you have a leak in your master cylinder and the booster pulls silicone into the manifold through the booster vacuum hose.

The article said that when the silicone burns it turns into granules and the granules wreak havoc on the engine seals/cylinders....whereas conventional fluid burns without harm.

Is this for real?

If that is the case, Dot 5 seems like too much of a risk compared to the benefits.

Any input here...I converted to Dot 5 and am considering going back to conventional.

Thanks

 

Well, I'm not sure that is a valid concern on our cars. I had a MC fail and leak fluid into the booster and none ever got into the intake manifold. If you look at the location of the vacuum port on the booster you will see there is a HUGE volume of space that would need to fill with brake fluid before it would rise to the vacuum port level so it could be drawn into the intake manifold.

 

Speaking as a chemist, when DOT 5 is broken down by heat, the only solid left behind is extremely fine silicon dioxide. You would not call those granules by any stretch, the technical term is fumed silica. Now, silicone dioxide is sand, but fumed silica acts more like ultra-fine polishing compound.

I wouldn't say that an engine that took in some fumed silica would be happy with it but I don't think it would destroy the engine.

I second Kenneth's assessment of the possibility of getting the brake fluid into the engine. You would lose your brakes long before any brake fluid got to the level of the vacuum port on the booster.

 

For brake fluid to migrate into the booster and be sucked into the intake, TWO seals would have to fail, the seal on the rear piston in the M/C and the seal between the M/C and the booster. As noted, this would be pretty obvious due to the crappy brake performance.

 

Thanks for the replies...and perspective.
Andy

 

I think the more significant concern is that silicone fluid won't absorb any moisture, so you can get beads or even puddles of water in the brake lines and cylinders if you are in a humid climate. DOT 3 and 4 fluids will absorb water, degrading their performance somewhat, but not catastrophically. Just change the fluid on occasion to keep it fresh.

 

Like most engineering systems, performance depends on the weakest link. The brake fluid is not the weakest link in our old cars; use what it is designed to use.

Reminds me of a safety question on some plant equipment at work. "If an earthquake happens, it could do this and cause lots of downtime." "If an earthquake happens, this will be the least of your problems." Same thing with the brake fluid being dried out and ruining an engine. After you lost all your brake fluid into the booster, and its seal then failed, and the engine started pulling some into the carb, and it were to get aerisolized, it wouldn't be burned until the combustion chamber, and might end up on the exhaust valve seal if anything. Hell you might even get some cleaning and a port and polish job.

There's a greater chance of my 442 causing some model chick to spontaneously love me and pledge her undying love and body to me on the spot; and it's a heap that leaves the garage once a year.

 

Thanks...that's why I asked...to get some perspective...risk does not appear significant.