View Full Version : Brakes: brake fluid

06-27-2012, 11:24 PM
As I was filling the new master cylinder with dot 3 today, I had a question pop into my head. Would dot 4 fluid be compatible with the Studebaker brakes? I have an old Land rover, and a 59 Morris Minor, both of which demand dot 4. Sure would be nice to just have one bottle...

06-28-2012, 06:29 AM
I used DOT 4 in my brakes and it works fine. The two are supposed to be compatible with boiling point the only real difference.

Years ago I helped rebuild the brakes on an 1960 MGA and we were told to use ONLY Castrol brake fluid. It might have been DOT 4 but I don' t recall. Then after that my father and I were working on an old jeep and all the rubber brake parts were swollen into goo. Dad said that Jeep used natural rubber and that normal brake fluid attacks it. He bought new rubber parts and Castrol brake fluid and everything was fine. Of course maybe someone dumped oil into the brake system and THAT is what messed it up.

Perhaps some old rubber parts used a rubber compound that reacts badly with modern brake fluid. I bet that new rubber parts don't have this problem. If you are already stocking DOT 4 for your UK cars then that should work fine.


06-28-2012, 08:22 AM
The Morris brakes were originally ruined by the PO putting in dot 3. ( natural rubber parts turned to goo, just as you said). Perhaps Castrol fluid is dot 4. Well, I put dot 3 in the Stude yesterday, so I guess that chemistry project is in the future.