DOT-5.1 Brake FluidDear Ole Mechanic;

I have an old 1952 Chevy pickup.  I restored it about ten years ago and only get it out for special occasions like the 4th of July parade.  I have learned to get it out a couple of days early, because for the past several years when I get it out, I have had to work on the brakes.  Last year it was a leaking rear brake cylinder, the year before that it was a leaking front brake cylinder and this year the brake pedal would slowly go to the floor.  I had to get a rebuilt master cylinder, because the fluid was leaking past the internal rubber cup. 

I'm tired of having to work on the brakes before I can go enjoy driving the truck.  Would you have any suggestions other than going through and replacing everything in the brake system every eight years or so?

Tired of Brake Work

Dear Brake Work;

Yes, in fact I do have a solution for your ongoing problems with the brakes in your restored Chevy.  It is called DOT-5.1 silicon brake fluid.  Now before you run out and start pouring it into your master cylinder, there are some drawbacks to the DOT-5.1 brake fluid that need to be covered.  Number one is it is expensive!  The last time I brought any it was in the $15 to $20 range for an 11-ounce container and your old Chevy will take three, maybe four containers to replace all of the brake fluid.

The second problem is that DOT-5.1 fluid is not compatible with any other brake fluid, so you must--repeat MUST--remove ALL traces of old fluid from your brake system.  You are going to need to disassemble the master cylinder and all of the wheel cylinders and clean everything with denatured alcohol--and I do mean clean everything thoroughly.  Then, you will need to flush all of the brake lines with alcohol thoroughly also, because there can not be any trace of old brake fluid left, as it will attract moisture and cause problems.  After things are absolutely clean, you can put it back together and start pouring in the DOT- 5.1 brake fluid.

Which brings us to problem number three.  DOT-5.1 fluid is a real pain in the back-side to bleed and get all of the air out of the system.  It just loves to trap air bubbles and you will need to go through the bleeding procedure several times.  Just when you think you are done, you may need to bleed the system again.

Is there any good news?  Yes, because I have seen restored vehicles with DOT-5.1 in them go for 25 years or more and not have any brake-fluid leakage or any brake-fluid related problems.  My suggestion to you would be to go ahead and enjoy your old Chevy this summer and start collecting a new or rebuilt master cylinder and new or rebuilt wheel cylinders.  Then, when something does start leaking, go all the way through the system.  That way, you will only need to alcohol-flush the brake lines and you won’t need to disassemble the master cylinder or wheel cylinders.--just replace them with the new or rebuilt ones.  Finally, use DOT-5.1 brake fluid and stick with it.  How did I find out about DOT-5.1?  An old friend of mine went through what I have just described on his old split window Corvette some 26 years ago, and the only brake work he has done on it is to replace brake pads that wore out.

Don’t get discouraged if you have trouble finding DOT-5.1.  I went into one of the national chain auto -parts stores in a nearby town.  When I asked for DOT-5.1 fluid, the person at the counter said that he had never heard of it.  However, when I checked the shelves in the brake-fluid area of the store, I found it.  The old truck that I finished restoring over a year ago has DOT-5.1 brake fluid both in the brake system and in the hydraulic clutch system.

Herr Professor Nuzanbolts