Brake fluid experts?
 

In my formula ford I have girling master cylinders. I have been using dot 3 synthetic. They have worn out with very little use. Dot 4 is recommended. Is it possible the dot 3 synthetic ate away the seals in the girling mc's?

There is a minuscule amount of difference between DOT3 and DOT4 fluids and it would have no effect on wear. The difference is between boiling points and freeze points.

Whaddya using the brakes for anyway? Getting timid in your advancing years?:P

The accelerated wear is probably being cause by moisture accumulation. How often are you changing/flushing the fluid?

You can't treat the FF as a car. I'd recommend no more than 10 hours brake use per flush.

I agree. ALL brake fluid is synthetic. Water is the most likely culprit. Could you use DOT 5?

Define " worn out " and how old the cylinders are.

Some older ( 60's ) Girling cylinders had seals for hydraulic oil not brake fluid. But anything more modern than that will be OK with regular brake fluid.

If fluids are mixed, the rubber expands to 2x it's normal size rather than disolving.

For autocross use, the fluid you are using is fine. When road racing my FF ( Zink Z10C ) regular fluid was just fine, I'd flush once a year and call it a day. These cars are not that hard on brake fluid unless you have inboard rear brakes and full body work.( no air flow )

I haven't been on this list for a while but you should probably have a look. apexspeed.com is a very good formula car centric site.

Yeah, I am a frequent visitor at apexspeed. In this case I am looking for a second opinion. In the past I have found the seals in the European brake systems very sensitive to type of brake fluid.

Worn out? I dunno what that means until I get it all apart. losing brake fluid and I don't know where is the exact def.;)

Thanks guys! In answer, I don't use them much but it is nice to have them when I want to.....and at the end of the run.

I would suspect the material the seals are made from...

yes? suspect them of what?

Those alloy MC bodies can be junk castings. It was normal to bore them & fit a sleeve, brass or stainless. You may be seeing problems with the internal alloy surfaces being too rough. Plastic bodies are now available. ~ you have 2 choices.

Where is the brake fluid leaking from?

How old are the cylinders?

After going through quite an ordeal installing both new master cylinders when I went to bleed them I found a leak in a line. Because it was located right next to the engine I had thought the leak was oil...silly now that I think about it. It was oily but the wrong color. Being synthetic it did not smell like brake fluid. So my old MC are probably still good.

Doh!