ctuinstra

I'm beginning to wonder about the choice of going to the silicone brake fluid. I don't race or drive the car hard. It does sit a lot so it was important to me that it not draw moisture. From the looks of things when I took it apart, that was a major issue. Back to the wondering about using it, I noticed while bench bleeding there is a lot of stiction with the rubber seals. If I let loose of the piston fairly quick it will retract most of the way and then the last 1/8" or so it will stick and then pop all the way. Doesn't do it every time but enough to make you wonder about the amount of stiction.

toobroketoretire

I made the switch to all-silicon DOT 5 about 2 years ago and within 3 months all 4 of my brake hoses had swelled shut because the OEM hoses aren't compatible with the all-silicon DOT 5 brake fluid. I replaced the hoses with modern J-1401 hoses and that did the trick. If you have an air compressor you can blow 120 psi into your master cylinder lines to purge the fluid out of your calipers (bleeders removed). You'll also need to remove the old DOT 3 from your master cylinder because the two fluids aren't compatible with each other. DOT 5 is a great upgrade for these old C3's but it can't be used with anti-lock brakes because the DOT 5 is slightly compressible.

ctuinstra

The good thing is that I'm in the process of completely rebuilding the entire brake system. The calipers have been torn apart, washed/painted, and upgraded to 0-rings. Same with the master cylinder as I'm currently bleeding it. I will be blowing out the lines with alcohol tomorrow. And I will be replacing the rubber lines with new stainless steel braided lines.

The big question is; can I get the full system to bleed completely. My dad never could get and keep a great bleed on it, I would love to be able to do that for him.

lionelhutz

I tried it in a car once with all new brake parts and it really didn't seem any better. When I flushed it there was crap in the fluid just like any other fluid changes color and looks dirty. Then, you have to be very careful and go very slowly with it otherwise you can get air into it that is hard to get out. I think there is some technical word for it, but basically you get microscopic air bubbles in the fluid that won't just bleed out. If moisture actually gets into your braking system, instead of it being absorbed by the fluid it just stays separated from it which is no better. Heck, the system is supposed to be sealed anyways so how does all this moisture get in there? You should still flush it periodically like any other brake fluid. Overall, I always hear how it's so wonderful but personally I just didn't see any real advantage. DOT4 works just as good to me.

As for your braking. Try filling the system and leave the bleeders open until fluid starts to run out of them. Also, you have checked the runout of the rotors so the calipers don't suck-in air, right?

toobroketoretire

I suggest Googling "Brake Fluid" and read what Wikipedia has to say about the different brake fluids and why the silicon DOT 5 has a big advantage over the others. DOT 5 can only absorb something like 1% water and that water stays in suspension. But the DOT 3 and DOT 4 continue to absorb water and it comes out of suspension; allowing liquid water to settle in the piston bores.

lionelhutz

Good for it. Once again, I have read a whole bunch of stuff about how good it is but the one time I tried it I found that it sucks. I flushed it out to get rid of it and the brakes bled quicker and had a better pedal feel with DOT4.

gungatim

bad advice, There a dozen better methods to flush brake fluid. blowing 120psi into anything is never a good idea. it only takes 5psi or so to move fluid. introducing all that air which includes moisture and likely some oil (unless an oilless compressor) into your lines is not a good idea. 120psi compressed gas is NOT the same as compressed brake fluid.

if nothing else, get a zip lock bag, cut a hole in the corner, stick it over the line, seal with a rubber band, and pour the fresh brake fluid in the bag and let it flush naturally. why introduce all those contaminants into your system?

Barry's70LT1

About 30 years ago I switched to SS calipers, new rubbers in the MC , new flex lines, and went with Silicon Dot 5 .
Bleeding was a non issue, "gravity", firm pedal, great brakes.

Haven't touched them since !

toobroketoretire

It takes a LOT of air pressure to completely purge the fluid out of the calipers with their top bleeder valves. I have triple 30 gallon air tanks plumbed together in series with my outlet on the last tank so the air I am blowing is free from moisture. The object of using high pressure is to remove as much of the old brake fluid as possible before introducing the new clean fluid. Maybe the air that comes out of your tank is full of crap but mine isn't....................

ctuinstra

They made DOT5 30 years ago? I thought it was recent.

ctuinstra

I did blow out the system tonight. Not quite with 120psi, but enough. I blew out the old fluid because it was more important to me to get the old fluid out of the lines. At this point it's just the lines, the calipers are on the bench along side the MC. After blowing the lines, I injected a syringe full of alcohol into the lines and blew that through each one (took to other helpers). I really don't believe the compressed air is going to add that much more moisture into the lines that the lines being exposed to the atmosphere and the alcohol should help to dry them up. I feel pretty satisfied the lines are as clean and clear as they are going to get short of replacing them with new.

TheSkunkWorks

While I actually think silicone brake fluid is probably a good call for use in rarely driven cruisers (no real need with SS), if you EVER decide to track it (RR) and/or drive in a highly-spirited manner for any length of time, I would strongly advise flushing it in favor of a premium grade racing fluid that won't expand at very high temps, such as Castrol SRF. My $.02

ctuinstra

Understood. This car will never see a track. It's a cruiser. Heck I drove around this past year on brakes that are no better then what's on a bicycle; lot's of downshifting.

ctuinstra

I understand the concept behind gravity feeding and I may just do that on this car. How do you keep from it overfilling the MC? I assume you hook one wheel up at time. You would need enough to fill the caliper and the lines, pretty hard to determine the exact amount.

Barry's70LT1

When I converted to Dot 5 (many years ago) it was not common to see Dot 5 in a car, however it was quite common in new motorcycles.
A bike shop was about the only place around here that had Dot 5.

I don't remember exactly the bleeding procedure I used then, however I believe I opened all bleeders at once in the beginning. Then shut down each wheel as they began to show fluid. You need to monitor the fluid level in the MC.

I then bled each wheel separately after that. I do remember using a small rubber hammer extensively. Tapping the lines everywhere as well as the calipers. The belief was to release any clinging/trapped air bubbles from the lines/calipers.

I think the final bleed was with someone inside on the pedal.
Don't pump the pedal fast, release the pedal slowly to give the fluid time to follow the MC piston and not suck air.