can you mix brands of brake fluid?

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Oct 13, 1999
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#1
My front brake is real spongy and it gets better when I pump it up. I can even see an air bubble through the sight glass. I plan to use my Mity-Vac to bleed the brakes but when I do this I need to add some fluid. Can I use any dot 4 fluid? If not, I will drain the whole system and start from scratch

Thanks

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Jay
2001 KTM 250 E/XC
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Chicken Wrist Racing
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yarbonwick

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#2
I was going to start another thread about brakes, but you cam up with a suitable topic. Last weekend while riding some really narly (does that start with a "g"?) woods riding (Bill's Woods - Muenster) my front brake kept going out. A few frantic pumps of the lever it came back. It would do this on a repeated basis. Any ideas? System has never been opened and now has one years worth of fluid. Think it's over do for a change? Maybe cooked the fluid?

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Lloyd TMTC #540 - Y2K KTM 250 E/XC
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Patman

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#3
I would believe you could mix the same type of fluid from different manufacturers but it would be better to just flush it completly. Just be SURE it meets the spec. called for. I use Motul DOT 5.1 because DOT 5.1 is called for on my bike.

Yarbo sounds like air or maybe moisture, flush it.

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clw

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#4
yarbonwick:

Something is displacing your pads from the rotor. Either the rotor is bent or you have an object jammed in your pads/caliper. Generally, if it's air it just plain feels mushy.

At least that's my experience.

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yarbonwick

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#5
That's what I'm attributing it to. Bill's Woods is very difficult (it's only about 5 miles but can take you well over an hour to get through!! Took us over TWO!!)
Yesterday I rode Sam Houston National Forest and never had the problem. So I'm attributing it to Bill's Woods wanting to take another casulty. It's a really-really difficult area. Thinking that mud or something interferred with the pads. However, I also believe it's time to flush the system and add new Dot 4.

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Lloyd TMTC #540 - Y2K KTM 250 E/XC
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[This message has been edited by yarbonwick (edited 04-19-2001).]

[This message has been edited by yarbonwick (edited 04-19-2001).]
 

Patman

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#6
It would seem to me if you had to "pump" the brake a few time to get it back and it happend several times that what was displacing the pad was air not allowing the fluid to force the piston out. This air space could even come from moisture in the system which evaporates when it gets hot enough leaving once again air. If a rock / twig / mud was causing the pad not to contact would it not be consistantly gone?

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yarbonwick

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#7
Good point. In either case the fluid is going.

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Lloyd TMTC #540 - Y2K KTM 250 E/XC
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#8
Brake fluid absorbs moisture, drastically lowering boiling point. Suck/wipe out the master cylinder. Fill with fresh Dot 4 or Dot 5.1 (Not Dot 5, the silicone stuff).

My favorite is now Valvoline Syntech brake fluid available most anywhere. I use it in all my vehicles. I'm a fatboy 235lb aggressive on the brakes A enduro rider. Good, cheap preventative maint....

Change it out every 2 years on your cars/trucks, your brake sys will last forever. I flush my dirtbikes about every 10 races or yearly at a minimum, and I live in dry AZ.

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