DOT 5 brake fluid problem - Saxperience

karl_mh · 15th September 2018, 18:58

Ive just completed the modification of my braided brake lines to fit a newly installed Satchshift hydraulic handbrake, prior to me getting my hands on the car the brake lines were already primed with brake fluid. During the brake line mods I've had to drain the fluid and I'm now at the point of replenishing the lost fluid, however, after further investigation I've discovered that the fluid is what I think is DOT 5.

Anyone out there a brake fluid oracle?

Based on what information I can find on the inter web it seems the DOT 5 is purple in colour - this appears to be the same colour as mine.

From what I can gather, you can't mix DOT 3, 4 or 5.1 with DOT 5 "they say" its not really used as a performance braking fluid unlike DOT 4 so this now poses a problem......is it possible to completely flush out the DOT 5 and replace it with DOT 4 without any adverse effects to the braking system / seals? I've read some horror stories about mixing the two, anyone had the same issues.

Others also say that the pedal can get a little spongy which in my book is never good.

Quick · 15th September 2018, 23:26

Test a small sample to see if it mixes with water!
No mix dot 5!

MartinObviously · 15th September 2018, 23:49

Are you sure it's DOT5 you used? It's surprisingly expensive and difficult to come across by accident - it's the silicone based one. Every other DOT is glycol based.

You can buy DOT 5.1 fluid in blue colour - which is glycol based and safe to mix with DOT4.

As above though, if you put some of (what you think is DOT5) in water, it should separate and sit on top of the water. if it's glycol based, it'll mix with the water and not separate.

karl_mh · 16th September 2018, 08:33

Thanks chaps for your responses, I'll get a sample and test it this morning

unfortunately when I bought the rolling shell the braided lines to the old hydraulic handbrake were freshly made and the system filled and primed with the mystery solution, I didn't even click when draining the fluid so I'm not 100% sure it's DOT5.

I do hope it's DOT 5.1 with a hint of blue dye!

karl_mh · 16th September 2018, 14:37

Here goes! some pics of the brake fluid in water. Cant get the videos attached of the fluid going in for some reason?

The stuff currently within my system (poss DOT 5)

karl_mh · 16th September 2018, 14:46

Dot 5.1

karl_mh · 16th September 2018, 14:51

DOT 4 mixed with water

karl_mh · 16th September 2018, 14:55

TBF they all seem to appear the same when going into the water and all of them dissipate into the water, I only had approx 10mm of the my mystery blue stuff in the end of a straw. Hopefully from whats been said the blue stuff should remain separated from the water if its 5.1

SpijkerVTS · 16th September 2018, 18:12

Ive used dot 5 for years, its normally yellow like nor.al brake fluid it cant just cope with higher temps so you get less brake fade bassically

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MartinObviously · 16th September 2018, 18:25

Quote:

Originally Posted by karl_mh

TBF they all seem to appear the same when going into the water and all of them dissipate into the water, I only had approx 10mm of the my mystery blue stuff in the end of a straw. Hopefully from whats been said the blue stuff should remain separated from the water if its 5.1

It would float on top of the water straight away if it was 5.0, it wouldn't mix or sink etc.

Sounds to me like it's had 5.1

karl_mh · 16th September 2018, 20:12

Well.....I think the mystery is solved thanks to everyone who suggested the water & brake fluid dilution test

I managed to get a full straw full of the blue brake fluid to dilute with the water, here are the results!

It looks like I have DOT 4 / 5.1 and not the dreaded silicone based DOT 5, the bottles are not in any order.