Converting to Silicone Brake Fluid

[Terry M.]

Re: Converting to Silicone Brake Fluid

SAE paper 810804 is a good reference on this topic if you can get it.

It says... "It was found that silicone brake fluids performed as well as or better than conventional fluid in all tests involving brake system elastomers...."
It goes on to say "brake performance of systems in which silicone and conventional brake fluid become mixed will operate normally with no fluid/elastomer based problems."

I would interpret that as meaning a few drops of conventional brake fluid left after a careful flushing of the system with silicone fluid isn't going to hurt anything on an old Corvette.
I have had it in my car for over 20 years with no problems at all

John,
Several decades ago, when I got three or four SAE papers from them, the one that sticks in my mind contained an examination of several systems that were introduced to DO5 in the manner you reference. Those were military vehicles that were subsequently stored in Panama. A dark sludge (for want of a better term) formed inside the brake system, and the researchers concluded this was as a result of the lack of complete removal of the polyglychol fluid. They noted that the sludge appeared to be harmless, however. I am not sure if that is the paper you have.

The label on the cans of Dow DOT5 that I have from many decades ago actually recommend flushing the DOT5 through the system as a means of removing the polyglychol fluid.

I chose not to use that method, but my system was already more than partially disassembled, so the choice was easier.

[Siegfried K.]

Re: Converting to Silicone Brake Fluid

What is the best method of flushing the calipers of old DOT 3 fluid? Should they be removed and disassembled, or is there perhaps an easier way.

[Jim T.]

Re: Converting to Silicone Brake Fluid

What is the best method of flushing the calipers of old DOT 3 fluid? Should they be removed and disassembled, or is there perhaps an easier way.

Siegfried are you going to convert to silicone brake fluid?

[Siegfried K.]

Re: Converting to Silicone Brake Fluid

Yes Jim, I am converting to Silicone. My apologies, I should have made that clear.

[Duke W.]

Re: Converting to Silicone Brake Fluid

See post #5 and #15.

Duke

[John D.]

Re: Converting to Silicone Brake Fluid

Getting every last molecule of conventional brake fluid out of the system would provide only a theoretical benefit based on the study referenced in the SAE paper in which even the highest mix proportions of both types of fluid in tropical conditions failed to induce any brake performance issues.So the question you need to ask is what's the value of disassembling the entire brake system to make the change in terms of cost and time....relatively high.What's the risk of any brake problems with a residual amount of regular fluid after a careful flush with the silicone fluid ?...based on the data in the SAE paper and my personal experience very, very low.

[Duke W.]

Re: Converting to Silicone Brake Fluid

For what period of time did they evaluate the performance? That's a critical question as it may take time - years - for problems to develop.

If you start with every component clean and dry and assemble and properly bleed with DOT 5, you can just about forget about the brake system maintenance other than pad/shoe inspection/renewal for several decades.

Terry mentioned the "dark sludge", from his SAE paper reading, and maybe it didn't affect brake performance in the short run, but what about the longer run? Regardless of short term performance, I don't want sludge in my brake system. The only acceptable medium is clean, moisture free homogeneous fluid.

Having owned my cars from 23 to 51 years I know the long term - in some cases not so long term - effects of moisture contamination in conventional brake fluid. The master cylinder failed on my SWC in 1968, so it only took five years for corrosion to take a toll. Similarly with the Cosworth Vega - the rear wheel cylinders had internal corrosion after five years. At that point I got religion!

On my cars that still have conventional fluid I flush the systems with a quart of fresh DOT 4 every two to five years, depending on how much weather exposure they've had. When I completely rebuilt the J-65 system on my SWC in the seventies, it was a convenient time to switch to DOT 5, so I did using the method I prescribed in previous posts.

When it comes to the brake system I don't take shortcuts, and don't recommend that anyone else do so, either.

Very few current vintage Corvette owners have owned them since new and/or have detailed service records since they were new. So most have no idea of the internal condition of their brake system, and based on my experience, many are in less than good condition and are bound to fail. It's as easy as removing the master cylinder cap to inspect the fluid. It it looks like day old cold coffee, you're gonna have a problem!

Flushing out conventional fluid with DOT 5 is likely no more than a stop-gap measure, so why not go through and renew the entire system. And if you assemble and fill the system with DOT 5 you can be confident that the hydraulics will function properly as long as you own the car and probably for the next several owners.

Duke

[Brian K.]

Re: Converting to Silicone Brake Fluid

When I bought this car in 1986, it already had sleeved calipers. I put in a new master about 15 years ago & new lines about 5 years ago. Only one caliper leaked about 5 years ago. Fluid was flushed a few times over the years mostly for these items. Since the others are fine but can't be far behind, so a rebuild is in order. I figure silicone would end the maintenance issue. BTW, the master isn't re-buildable because of corrosion on the bottom where water sat. I got pretty good life from dot 3.

[Terry M.]

Re: Converting to Silicone Brake Fluid

The key to a longer lived brake system with conventional fluid is Dukes statement about flushing the system every couple of years; which = maintenance. ALL the daily drivers in my household use conventional fluid due to their all being equipped with anti-lock brake systems. I flush that fluid (no I do not have the Tech II to operate the anti-lock brake pistons) every couple of years. I believe flushing the majority of the system is sufficient. The hydraulics of these systems have given me no problems. Two of those cars have been in my possession for well over a decade and each has close to or above 250K miles and they are no stranger to heavily salted roads. All three cars have sliding calipers (unlike the Corvettes) and the major maintenance issue has been keep the sliding mechanism lubricated and free of corrosion. For daily driverfs an ounce of prevention is far superior to waiting for failure and dealing with the results.

[Claus S.]

Re: Converting to Silicone Brake Fluid

Do you think that silicone break fluid can prevent brake calipers from leaking as Phil said in an earlier post?

[Terry M.]

Re: Converting to Silicone Brake Fluid

Do you think that silicone break fluid can prevent brake calipers from leaking as Phil said in an earlier post?

DOT5 will not, by itself, cure leaks. It is not a miracle fluid. The reason for the leaks must be found and corrected regardless the brake fluid used. I have heard complaints of caliper seal leaks in cars stored for extended periods. The operating theory is that the constant weight of the aluminum pistons causes the seals to deform. It is hard to beat gravity. I believe this is a function of inferior caliper seals and the solution is to find (and I admit I don't know where) quality piston seals.

[Phil W.]

Re: Converting to Silicone Brake Fluid

Do you think that silicone break fluid can prevent brake calipers from leaking as Phil said in an earlier post?

Claus, I can only tell you what my experience has been. After years of frustration, replacing one caliper at a time, time after time and many times the on same corner, I was talking with Steve Hack at Eastern Corvettes and he suggested switching over to silicone saying he had good luck with this conversion. Rather than tackle this job myself, I got Steve to replace all 4 calipers, the master cyclinder and all rubber brake lines. We left the steel brake lines as they were in pretty good shape. He also completely flushed the system mutiple times in the process.
Since that time, about 7 years ago - I think, I haven't any problems at all. My car sits unused for long periods as I'm sure most eveyone's does. If I don't drive it, I do try to pump the brake pedal at least once a month to keep the caliper pistons loose and moving.
I hope this helps - for me it was the best money I've spent on my '71 in the 29 years I've owned it. Phil

[Timothy B.]

Re: Converting to Silicone Brake Fluid

I also want to add that reused older caliper pistons that have suffered corrosion damage from the dot 3 and air can pass fluid so keep this in mind.

IMO, changing to silicone fluid has nothing to do with caliper leaks, I believe it's like described in post #26 about the weight of the pistons and gravity. It was recommended to pump the brake pedal every now and again to keep the rubber lip seal round, I seldom do it though.

The only problems I ever had with leaks were in the rear and I think the brake rotors are on the wrong side as there is run out to the point I hear squeak squeak squeak out the drivers side rear so you know it's pumping the pistons some. This stops as soon as touching the brake pedal.

[Claus S.]

Re: Converting to Silicone Brake Fluid

I wonder if i should go for silicone brake fluid since the calipers, brake lines and hoses are brand new for my car and not yet installed
Then i should not have any worries that other than silicone brake fluid is in the system

[Terry M.]

Re: Converting to Silicone Brake Fluid

I wonder if i should go for silicone brake fluid since the calipers, brake lines and hoses are brand new for my car and not yet installed
Then i should not have any worries that other than silicone brake fluid is in the system

With all new parts this is certainly the time to make the change to DOT5, if you want to. Even with new lines I would still flush them (after installation) with alcohol and blow them out with compressed air as there is no telling what has gotten into them during manufacture, storage, and shipping. Some insects like these kinds of places and they would not be helpful in stopping your car. Other debris could get in there as well. Cleaner is gooder.