Dot 5? (1 Viewer)

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We're replacing some brake parts on a '87 Grand National, and we're thinking about changing to DOT 5, since it isn't driven much. What are the advantages/disadvantages of DOT 5, and how should we go about flushing the system, if we do change to DOT 5?
Thanks,
Trevor
 
DOT 5 is silicone based. Cannot mix with any other brake fluid- you need to flush the system really carefully in order to not contaminate the new fluid and if I remember correctly DOT 5 doesn't absorb moisture the way DOT 3 or 4 does. If any moisture gets into the system, it is heavier than the fluid so it sinks to the lowest point (maybe your calipers), so that when your rotors get hot, the water boils and makes a vapor-lock kind of situation. Also, some older cars have rubber pieces in the braking system that don't tolerate silicone fluids. The only real advantage is that if not contaminated it has a much higher boiling point than DOT 3 or 4.

Luke
 
LukeZero said:
DOT 5 doesn't absorb moisture the way DOT 3 or 4 does. If any moisture gets into the system, it is heavier than the fluid so it sinks to the lowest point (maybe your calipers), so that when your rotors get hot, the water boils and makes a vapor-lock kind of situation. Also, some older cars have rubber pieces in the braking system that don't tolerate silicone fluids. The only real advantage is that if not contaminated it has a much higher boiling point than DOT 3 or 4.

The problem with cars that are not driven often is that moisture from the air is absorbed by the DOT 3/4 and it gets contaminated, then components rust. The DOT 5 resists this absorbtion, so it keeps the components from rusting.

If you pour water into it, bad things will happen, for sure. Don't.

True about some older seals. US Mfgrs say they've been compatible for a long time, since sometime in the 90s.

FWIW, I have DOT 5 in my fj40. It's an experiment, let's say. It's been a couple months, and it's working fine. We'll see in a couple years.
 
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