DOT5 ok?
Burning Brakes
Joined: Nov 2004
Posts: 988
Likes: 4
From: Livermore CA
No, DOT 5 is fully synthetic and doesn't mix with DOT 3 and 4 so you end up with little pockets of old DOT 3 and 4 which become totally saturated with moisture. DOT 5 is great stuff, it doesn't absorb water and has a high boiling point but they recommend that you completely clean out (meaning flush with alcohol and dry) any remnants of DOT 3 or 4 before pouring in the 5.
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
No, DOT 5 is fully synthetic and doesn't mix with DOT 3 and 4 so you end up with little pockets of old DOT 3 and 4 which become totally saturated with moisture. DOT 5 is great stuff, it doesn't absorb water and has a high boiling point but they recommend that you completely clean out (meaning flush with alcohol and dry) any remnants of DOT 3 or 4 before pouring in the 5.
Racer
Joined: Nov 2019
Posts: 336
Likes: 173
From: Canadian living in southern France
I'm changing all the flex hoses on my '76, and will change all the fluid while I'm at it. It has DOT 3 or 4, and that's what I'm going to put back in, because I plan to change it every couple of years.
But, back in about '98, I completely rebuilt the brakes in my Triumph Spitfire, (don't laugh, it's a fun little car), and put in silicone fluid, after flushing with alcohol and drying it out. It's been there ever since, have never had to add any, it has a hard pedal, it's in the clutch hydraulics too, and have never had any problem of any kind.
I'm thinking the material used in brake components has changed, and if manufacturers don't recommend it, I wouldn't use it.
I'm converting the Triumph to a solid rear axle, and after installing new wheel cylinders, figuring out a flex hose, etc, will have to bleed the brakes. I'll flush the DOT 5 out and go back to 3, and just change it regularly. Why take chances?
But, back in about '98, I completely rebuilt the brakes in my Triumph Spitfire, (don't laugh, it's a fun little car), and put in silicone fluid, after flushing with alcohol and drying it out. It's been there ever since, have never had to add any, it has a hard pedal, it's in the clutch hydraulics too, and have never had any problem of any kind.
I'm thinking the material used in brake components has changed, and if manufacturers don't recommend it, I wouldn't use it.
I'm converting the Triumph to a solid rear axle, and after installing new wheel cylinders, figuring out a flex hose, etc, will have to bleed the brakes. I'll flush the DOT 5 out and go back to 3, and just change it regularly. Why take chances?
Intermediate
Joined: Aug 2019
Posts: 37
Likes: 7
Regular DOT 5 is no good you could use DOT 5.1, but it does not get you anything over DOT4 for the clutch. On the clutch I use DOT 4. For the brakes DOT 5.1 which has higher boiling point and lower viscosity has some advantages and is what I use.
