Technical DOT 5 BRAKE FLUID

I spent some years working in a brake shop. Saw the occasional cylinder where a seal had turned to jelly with Dot 5.
It seems not all brake seal manufacturers use exactly the same formula for their rubber.. Most seem to work fine, but only one failure means trouble.
Dot5 does not absorb water, but does not prevent moisture getting into the system - normal atmospheric condensation etc. This forms little globules that migrate around the system, eventually ending up in wheel cyls or calipers where they can cause corrosion, or with severe braking can form steam with a very spongy pedal.
Some users of Dot 5 have had good results, but many have had problems.
All but a very few OE manufacturers use Dot 3 or 4 without problems. For me, I use Dot 4 every time.
Garpo

 

A brake system is sealed , how does enough atmospheric condensation enter a sealed system to cause problems in a reasonable amount of time .
Another point for you for dot 5 guys , a container of fluid is supposed to be a one use deal , ideally, i.e. use it and toss the remainder ...However , I think that might be Overkill...

 

I've seen seals turn to mush with DOT 3 when someone cleans the cylinders with mineral spirits, ans then blows them dry. The little bit of oil residue wrecks the seals. That could have been the case here as well.

 

6 years ago,I went to the U Pull It and got a used 1994 Jeep pedal assembly, brackets, booster, master cylinder and proportioning valve with brake lines all attached. Poured out the old Dot 3 and installed all this on my old Ford and added used disc brakes from the U pull It. Didnt flush out the old fluid, and these brakes have been working excellent ever since.
I also poured half and half Dot 3 and Dot 5 in a cup and watched it for a year until I accidentally knocked it over. Dot 3 and 5 mixed do NOT jell.
Some people worry too much