Master cylinder rust prevention

Boy good luck with this one...I look forward to the responses.

I know people that have go as far as to have them ceramic coated (disassembled first) for show cars and they still RUST!

I have a set of kids water color paint brushes I keep around. I just touch up the cast iron when it rusts near the cap with the manifold paint I painted the M/C with. Eastwood has this stuff you rub on bare cast iron to make it look new again also.

Like I said, this one has my interest up. I have been able to keep the calipers looking new, but the master, for some reason, likes to rust. It was BRAND NEW from a box when I installed it too.

Blast it, paint it with black catalyzed paint and then change your brake fluid over to silicone.

Concur on the Dot 5 silicone brake fluid, tho I don't

have the solid brake pedal feeling as with the Dot 3

fluid.

The only mod I did on my K was to put a dual reser-

voir MC and never painted it...NO rust in more than

8 years! Might it have something to do with the Dot

3 fluid being hygroscopic or is it hydroscopic, anyway

that's the ability to take up H2O.

Another positive with Dot 5 is it won't eat paint like

under the proportioning valve when it starts leaking.

<img src=images/icon_smile_cool.gif border=0 align=middle>

Charles I expected an educated reply from you. But I thought there was a reason I didn't use DOT 5 silicone fluid...wish I could remember what it was.

I did use DOT 3 Prestone Fluid which the label says is now silicone also. It must be, because I dripped some on the gear box and it didn't eat off the paint.

But the master still rusted in random spots, and most cars I look at have the whole thing a solid block of rust when the rest of the car is perfect. I only painted mine with clear engine paint. Not catalyzed paint, as I wanted the cast iron look since i have a dual master. I have since repainted with Eastwood cast iron and so far so good.

<BLOCKQUOTE id=quote><font size=1 face="Verdana" id=quote>quote:<hr height=1 noshade id=quote>

Charles I expected an educated reply from you. But I thought there was a reason I didn't use DOT 5 silicone fluid...wish I could remember what it was.

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana" size=2 id=quote>

'Cause the brakes are more spongy with silicone?

<BLOCKQUOTE id=quote><font size=1 face="Verdana" id=quote>quote:<hr height=1 noshade id=quote>

I did use DOT 3 Prestone Fluid which the label says is now silicone also. It must be, because I dripped some on the gear box and it didn't eat off the paint.

But the master still rusted in random spots, and most cars I look at have the whole thing a solid block of rust when the rest of the car is perfect. I only painted mine with clear engine paint. Not catalyzed paint, as I wanted the cast iron look since i have a dual master. I have since repainted with Eastwood cast iron and so far so good.

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana" size=2 id=quote>

Mine has started to turn brown, so I'd like an answer too. Can ya' get them powder-coated?

I agree 100 % with Charles. The original

master cylinder for disc brakes were painted

black and silicone fluid doesn't remove the paint.

Spongy pedal!!! Have used silicone brake fluid in

my 67 Shelby for 25 years without any problems

what so ever. The trick was to clean (tear down)

the system completely to remove all of the "old brake fluid"

before filling it up with silicone. Have done this on my 65

as well and haven't touched it since 1992. That's 14 years

with the same fluid and never any problems like spongy pedal.

I will never use anything else on my cars.

/Bo

The only problem I have ever heard of with silicone fluid is when it's used on track cars. Silicone supposedly has a quicker boiling temperature than regular dot 3, so your brakes might fade if using them hard when racing.

I have never had problems with a spongy pedal when silicone was used. I always use the stuff on any cars I build, for driving or showing.

Several of my hot rod buddies use DOT5 in their cars and I plan on using it when my HiPo is done. They swear by it.

Spongy pedal is caused by trapped air - some guys had to bleed the system 3 or 4 times to get all the air out.

DOT3 fluid will draw moisture and this is why it turns black - I think it is called "hydroscopic".

Using DOT 3 wouldn't be such an issue with regard to MC rust if the disc brake cap & rubber gasket did a decent job sealing the MC, these things are terrible IMO. I use Castrol DOT 3/4 and change it out every two years, it's still clear after that time just a little more reddish in color.

Charles is right, DO NOT use DOT 5 if you are driving the car hard like racing or open track situations.

I know this is off the original question but the spongey brake pedal feel may be due the fact that silicone brake fluid can make older rubbers swell?

I still have Dot 3 in mine. What's the proper procedure for flushing the system and replacing with Dot 5 while still installed on the car?

Best is to replace or disassemble the calipers, wheel cylinders and master cylinder and clean them thoroughly. To flush out the lines, I have heard alcohol should be used.

I keep the outside of my MC covered with a light coat of WD 40. No more rust.

As a general practice we used denatured alcohol for flushing disassembled brake systems of contaminents for many years in my shop. It is still readily available in most hardware stores. We would also use it in race cars when changing from one brake fluid brand or DOT rating to another. The chemical property of denatured alcohol removes water from lines & other components.

I don't know if silicone brake fluid causes swelling as mentioned in earlier posts. Silicone is a rubber preservative, not a solvent.

Edited by - round2K on 10/06/2006 09:33:17

<BLOCKQUOTE id=quote><font size=1 face="Verdana" id=quote>quote:<hr height=1 noshade id=quote>

I keep the outside of my MC covered with a light coat of WD 40. No more rust.

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana" size=2 id=quote>

I just saw your post - I will put some WD 40 on mine tomorrow or Sunday. Thank you for the tip.