Datsun Roadster Forum-311s.org

Questions for the fluid gurus. (and not Irish Whiskey, I already have enough field research in that arena...)

I recently tried changing over to Lucas Synthetic DOT 3/4 brake fluid, and bled/flushed both brake and clutch systems.
(parts replaced recently - 3 years ago - and functioned fine since then. All pieces in clutch system, including braided steel line)

69 2000 with never a heat problem under the hood, runs cold if anything else.

So now I went on a backroads drive, and realized that each time I stopped for a break the heat soak was effecting the clutch system, I would get a sudden "non functioning pedal", but would pump it 6-8 times and it would go back to working, and then once driving never a problem.
Over the course of the same 2 day drive, brakes worked fine but pedal traveled farther and farther towards the floor over the course of 2 days.

On this system, I did notice (on a slope) that when I held up the hand brake, the pedal noticeable "jumped up" to a much firmer feel and way less travel.

So adjusting the hand brake linkage is an obvious start, but has anyone else used this fluid and had strange results?

Thanks to all for the assistance.

Is it silicone type synthetic ?
The only way to use it is brand new cylinders ...you cannot switch to silicone after it has had reg fluid
It will do what you described

Not silicone, that is DOT 5.
This is dot 3 & 4 compatible, or so it says...

Sounds like the piston slave or master is jamming at the end of cyl
Because you say pumping restores a pedal
Fluid leaking out the open end of either ?
But brake fluid is extremely tough on rubber piston cups

This is the first that I have ever seen about not using silicone after mineral fluid. Everything that I have seen says to just give it a good flush with the silicone. The situation with the parking brake is the way that all that I have seen work. It sounds to me to be just a little air still in there.

Maybe check the adjustment of your rear brake shoes. This will take the up the slack like the e-brake and require less pump to get the rear cylinders engaged to contact the drums.
Rustbucket

C.Costine wrote: ↑Tue Nov 05, 2019 10:30 pm This is the first that I have ever seen about not using silicone after mineral fluid. Everything that I have seen says to just give it a good flush with the silicone. The situation with the parking brake is the way that all that I have seen work. It sounds to me to be just a little air still in there.

My dot 5 silicone bottle says it -only for dot 5 systems
The brake master has a silicone seals
When silicone fluid hits reg brake fluid it starts to make small gummy granuals like rtv adheisive that can clog the lines poporstioning valve. Our tech trainers at Mitsu suggested it would be good for clutch systems back when it came out in. 03? I tried it on my DD. as the clutch slave went out and I replaced the clt.master 3 or 4 month before .clean the system then purge with the dot 5 , worked but in summer heat it failed finding many tiny rubbery granuals in both that defeated the seals