Yellow gunk in brake reservoir?

[Asher]

My friends master cylinder has stopped working and his reservoir has got this yellow gunk in it after a fluid change.
He was using Dot 4 fluid and replaced it with Dot 5.1 and he thought this might have cause a reaction but everything i have read says Dot 3-4-5.1 are all compatible with Dot 5 the odd one out.

Has anyone seen anything like this before and what do you think caused it?

[FJRider]

They are different formula's.

Your friend should drain and clean the lines before replacing with the (new/different) brake fluid.

[Asher]

Thats what im thinking too, although one would think that the entire point of the Dot standards is to avoid this sort of thing.

[FJRider]

Thats what im thinking too, although one would think that the entire point of the Dot standards is to avoid this sort of thing.

Dot 4 ... Dot 5.1. ..... a bit of a clue they are each a different standard ...

[AllanB]

No issue going from 3 to 4 to 5.1 as they are all glycol based - the difference is their boiling point, higher as the numbers rise. I would add a full change of fluids should be done - not a top-up. I went from 4 to 5.1 with no issues at all.

Dot 5 is silicone based and must not be mixed with 3, 4 or 5.1.

Has he 5 in there? I suspect he has grabbed 5 not 5.1.

[Asher]

No issue going from 3 to 4 to 5.1 as they are all glycol based - the difference is their boiling point, higher as the numbers rise. I would add a full change of fluids should be done - not a top-up. I went from 4 to 5.1 with no issues at all.

Dot 5 is silicone based and must not be mixed with 3, 4 or 5.1.

Has he 5 in there? I suspect he has grabbed 5 not 5.1.

Yeah thats the same info as i have found but he is certain that he used Dot 4-5.1
I cant find any examples of anyone mixing Dot 5 with 3-4-5.1 so im not sure what that will look like.

[jellywrestler]

No issue going from 3 to 4 to 5.1 as they are all glycol based - the difference is their boiling point, higher as the numbers rise. I would add a full change of fluids should be done - not a top-up. I went from 4 to 5.1 with no issues at all.

Dot 5 is silicone based and must not be mixed with 3, 4 or 5.1.

Has he 5 in there? I suspect he has grabbed 5 not 5.1.

fuck, with all those numbers you'd be pretty well good at housie?

[AllanB]

fuck, with all those numbers you'd be pretty well good at housie?

Legs 11

88 two fat ladies

[boman]

Yeah thats the same info as i have found but he is certain that he used Dot 4-5.1
I cant find any examples of anyone mixing Dot 5 with 3-4-5.1 so im not sure what that will look like.

Look at your pictures. That's what it looks like to my memory.

I had to help someone clean out all their lines after they mixed DOT 4 & 5 together.

The mess resembled your pictures.

[AllanB]

Look at your pictures. That's what it looks like to my memory.

I had to help someone clean out all their lines after they mixed DOT 4 & 5 together.

The mess resembled your pictures.

Agree - if he still has the bottle I'd wage it is 5.0 NOT 5.1 ......

Nice avatar ....

[AllanB]

All the manuals for the bikes I have owned have been pretty specifc about what number brake fluid to put in and nothing else. If you crash with a different brake fluid in you may not have insurance cover.

Yeah because your insurance company take brake fluid samples, boil them so they know the boiling point then assess if they are dot 4 or 5.1 .......

And then they check your oil to see if you had dino, semi-synthetic or full synthetic and check the oil weight against factory settings and determine if you deviated.

Then they inspect the tyre pressures and see if the match the factory recommendations.

And fuck me if you repainted anything you are totally stuffed.

[Kickaha]

If you crash with a different brake fluid in you may not have insurance cover.

You certainly haven't got any more intelligent

[Shaun Harris]

Yeah because your insurance company take brake fluid samples, boil them so they know the boiling point then assess if they are dot 4 or 5.1 .......

And then they check your oil to see if you had dino, semi-synthetic or full synthetic and check the oil weight against factory settings and determine if you deviated.

Then they inspect the tyre pressures and see if the match the factory recommendations.

And fuck me if you repainted anything you are totally stuffed.

Technically he is CORRECT ( Extreme yes, but correct) re the brake fluid. If an inspection of the fluid was done by the accessor, and he showed it had the wrong fluid in it, an insurance company could walk from the claim, as the bike was technically unsafe to be on the road, wof or no wof

[Big Dog]

Technically he is CORRECT ( Extreme yes, but correct) re the brake fluid. If an inspection of the fluid was done by the accessor, and he showed it had the wrong fluid in it, an insurance company could walk from the claim, as the bike was technically unsafe to be on the road, wof or no wof

Would that not only be so if you could be shown to have crashed due to brake failure and had fluid of a lower spec than specified?
My manuals have all stated a minimum rather than a specific spec.

Sent via tapatalk.

[schrodingers cat]

Nothing comes for free of course - the higher heat rated, silicon based fluids suffer from a little more compressibility and are more hydroscopic.

Unless you've ever actually boiled your brake fluid I cant see the point (esp for road use) to go any higher than DOT4.
In fact simply freshening the fluid every so often gives a better result than a 'better' fluid.
Want more feel? - get a different pad compound

If the brakes have had a real hiding - bleed them. A couple of pumps to get any old fluid out of the caliper and away you go again