Brake Flush to Replace with Silicone

Grizzly · 06-20-05, 11:28 AM

I took JohnZ's advice and put a little of my brake fluid from my '67 in a test tube with some water and all I got was a milky mix so I guess I have standard brake fluid.

My question is are there any things I should be on the lookout for when flushing. Any special tricks? I have both a vacuum and a pressure bleeder.

I don't know if I have stainless brakes or not, but some have said if they are still working they must be stainless. Doesn't give me much comfort. The brakes are very heavy ( no power assist ) but I can stop the car and it pulls straight. I have no experience with non-assisted disc brakes so nothing to use as a standard. I would assume that the lining compound would have a lot of effect on how heavy they would be. Anyone have a suggestion for lining material that would not be too dirty and might be a little easier on the right leg?

Thanks...................

JohnZ · 06-20-05, 12:18 PM

I don't recommend the fluid change without disassembling and cleaning the components, but if you're convinced you need to do it, flush it thoroughly with denatured alcohol, then fill and bleed it (very gently) with the DOT5 fluid after bench-bleeding the master cylinder to get the trapped air out of the bore. DOT5 entrains air in very tiny bubbles and doesn't like to be agitated, as that just makes the bubbles smaller and nearly impossible to bleed out (which is why you can't use it with ABS brake systems).

OEM organic pads will reduce the pedal pressure somewhat; semi-metallic pads will increase pedal pressure significantly. Our power disc brakes on daily drivers have spoiled us in terms of what we think is "normal" pedal pressure, but the manual discs work fine - you just have to get used to the difference.

Grizzly · 06-20-05, 12:57 PM

I suspected as much with the flush.

As to what I do now, if every things seems to be working and there are no leaks, why not just flush with with Dot 3 every fall/spring? I know that Dot 5 will not absorb water and I believe it has a higher boiling point, but for a show car/driver is there any real advantage? Obviously if we get to a point where there are leaks/malfunctions then everything comes down and is rebuilt with stainless components.

Thanks for your response..................

magicv8 · 06-20-05, 02:37 PM

The only extra advantage comes when you get a drop or two on the paint job. With dot5, you can wipe it off and the paint will still be there.

critchie · 06-20-05, 04:48 PM

You're right. Don't bother to switch over to silicone (DOT 5). Just flush your DOT 3/4 every few years, and you'll be fine.

If you want to use silicone, you should really start with everything new. Something you might think about if you were rebuilding your brake system. But for an operating system in good condition, the benefits of silicone don't justify replacing everything.

BTW, how many "civilian" cars do you think get their brake fluid changed in their lifetimes? (OK, not counting the German cars whose owners read the manual.)

Viet Nam Vett · 06-20-05, 06:20 PM

Quote:

Originally Posted by magicv8

The only extra advantage comes when you get a drop or two on the paint job. With dot5, you can wipe it off and the paint will still be there.

To me that is a big advantage..as I am clumsy..and I drop and spill everything. I have already managed to drip some dot 5 on my paint...don't ask me how as I had the car covered in the aera I was working on in towells.

It felt good to be able to wipe up the fluid and have my paint stay on the body and not come off on the rag.

So....It's go old Non water absorbing $10.00 Bucks a small bottle of Dot 5 for me..!!

BarryK · 06-20-05, 07:19 PM

geez Mark, is there anything you don't drop on your body? brake pads, brake fluid....... what's next?

Viet Nam Vett · 06-20-05, 09:55 PM

Quote:

Originally Posted by BarryK

geez Mark, is there anything you don't drop on your body? brake pads, brake fluid....... what's next?

Don't go their....You"ll Jinx Me....

ZRGator · 06-20-05, 11:30 PM

Quote:

Originally Posted by BarryK

geez Mark, is there anything you don't drop on your body? brake pads, brake fluid....... what's next?

Now how can you bust on him when you dropped your entire body? BTW, when does that cast come off?....

TWINRAY · 07-07-05, 03:31 PM

I went with the opposite when my '67's calipers needed new seals. I got tired of paying $17/qt for the silicone fluid. I'm going back to regular brake fluid. I am putting new seals in all calipers and have blown out the lines with alcahol and flushed the master with same. I was under the misconception that being the silicone does not absorb water, you will not have a problem with condinsation. That is not the case. Now while I didn't do annual bleedings since I rebuilt the brake system in '89 (I am embarrassed to say I probably bled them twice since), the condinsation does puddle and the gunk/sludge that I found in the calipers was unbelievable. To those that think Silicone fluid is a bulletproof solution to your brakes, it is not. Brake systems with Silicone still have to be bled on a regular basis. That being the case, I'll use Castrol LMA fluid and this time I'll make sure that they will be bled annually. Promise.

All this being said, I have silicone in the '69. These (embarrased again) haven't been bled in 3 years. I have since purchased one of the Motol bleeding systems and will bleed those suckers with new silicone fluid.

Thanks to John for the advice he gave me on the alchol cleaning necessary when going from Silicone to "reg" brake fluid.

Kid_Again · 07-07-05, 04:06 PM

I followed JohnZ's advice with two modifications. I was able to get absolute ethanol (yup, with the tax stamp) and used that to clear the old fluid. It is much better at geting out all the emulsified water - one of my MCs had a fair amount of water in it. Each MC was also rebuilt. I then blew out each line (disconnected from the caliper) to dry everything out. One system was done with new calipers, on the other I disassembled the calipers and rebuilt them.

Both brake systems perform the same.

The major advantage of DOT5? My MC's stopped rusting on the outside.

I bought a gallon of DOT5 from Muskegon Brake for a very decent price and a fair amount was left over.

Viet Nam Vett · 07-07-05, 05:48 PM

Quote:

The major advantage of DOT5? My MC's stopped rusting on the outside.

Also.....It can be used for an "Evening" and or a "Party" Lubricant and will also Prevent Friction Burns on the Outside as well......

Mike McKown · 07-07-05, 10:47 PM

I have two cars that I didn't totally dis-assemble everything and clean it with alcohol before I went with the Dot 5. They have been fine for 4-5 years with no water residue in the system. Another car has a hydraulic clutch system and the normal four wheel drum system. It was just drained and flushed with Dot 5. Works fine. I don't recommened this for you but it works fine for me. If there is a contamination problem, what I have heard is that you will have water puddling in the low spots. Okay, even though silicone fluid I will flush these systems out eventually and the puddled moisture should come with it. All I know is, I can look in the master cylinder and the fluid in there and the reservoir are much cleaner than with Dot 3, 4 or 5.1

As has been mentioned, I don't have to worry about paint damage either. One drop of dot 3, 4 or 5.1 on your finish coat will cost you more to fix than a lifetime supply of Dot 5. It's worth thinking about.

Viet Nam Vett · 07-08-05, 10:59 AM

Quote:

One drop of dot 3, 4 or 5.1 on your finish coat will cost you more to fix than a lifetime supply of Dot 5. It's worth thinking about.

Well...Put..I agree.....By the way..What is Dot5.1?? What's the .1...Non Silicone?