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    Does brake fluid really eat through paint?

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    • Post n°1

    Does brake fluid really eat through paint? Empty Does brake fluid really eat through paint?

    Post by liverpool_f_ Thu 04 Feb 2016, 2:53 pm

    Does brake fluid really eat through paint?

    Yes it does, very much so. I did the front brake on my bike and I spilled some fluid on my bike to the following effect.

    Does brake fluid really eat through paint? Photo%201_zpsxcbk3gsx

    Does brake fluid really eat through paint? Photo%202_zpsrh9jewrs

    It only took a few minutes to eat its way through what it found contact with. Not a big deal as my bike looks rough anyway but it did lead me to find out a really handy tip. I tried this out subsequently and it worked really well.

    Apparently when BMW techs they are doing a brake job keep a little squirty bottle of water to hand so if some spills, in seconds they can give it a blast of water and the problem is solved. Brake fluid is hydroscopic so washes away very easily. Using the bottle keeps it from getting in the reservoir  like it might if you used a hose. 

    Just thought this little tip might save someone ruining their nice bike whilst doing a brake job!
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    • Post n°2

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by ratatooie Thu 04 Feb 2016, 3:10 pm

    This reminds me of something my mate told me the other day. He was working in the garage with his Dad. His Dad was changing the brake fluid on a car and my mate was doing something under the hood of another car. My mate looks up to a mist of fine particles of brake fluid wafting through the garage! His Dad was was using a compressor and air hose to blow the old fluid out! Needless to say my mate wasn't happy!
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    • Post n°3

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by eternally_troubled Thu 04 Feb 2016, 3:38 pm

    I've done similar things and yes, I agree, brake fluid isn't good for paint. It's not good to eat either Wink

    That's a good tip about having a bit of water on standby, just in case. Haynes (etc) suggest that you put a old blanket or dust sheet over the tank and any other vulnerable areas.
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    • Post n°4

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by Guest Thu 04 Feb 2016, 4:04 pm

    eternally_troubled wrote:It's not good to eat either Wink


    The taste lasts for ages, thank God for vacuum pumps!


    Last edited by teamster1975 on Thu 04 Feb 2016, 7:04 pm; edited 1 time in total (Reason for editing : Typo)
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    • Post n°5

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by Jameshambleton Thu 04 Feb 2016, 4:37 pm

    Protip, use dot5.1 and you won't get this problem! I typically only found out when I after I spilt dot4 all over my paint work too.
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    • Post n°6

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    Post by Guest Thu 04 Feb 2016, 5:17 pm

    So, it's a good paint stripper then scratch. Now that's an idea, I'll have to give that a try sometime.
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    • Post n°7

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by ashcroc Thu 04 Feb 2016, 8:06 pm

    liverpool_f_ wrote:Does brake fluid really eat through paint?

    Yes it does, very much so. I did the front brake on my bike and I spilled some fluid on my bike to the following effect.

    Does brake fluid really eat through paint? Photo%201_zpsxcbk3gsx

    Does brake fluid really eat through paint? Photo%202_zpsrh9jewrs

    It only took a few minutes to eat its way through what it found contact with. Not a big deal as my bike looks rough anyway but it did lead me to find out a really handy tip. I tried this out subsequently and it worked really well.

    Apparently when BMW techs they are doing a brake job keep a little squirty bottle of water to hand so if some spills, in seconds they can give it a blast of water and the problem is solved. Brake fluid is hydroscopic so washes away very easily. Using the bottle keeps it from getting in the reservoir  like it might if you used a hose. 

    Just thought this little tip might save someone ruining their nice bike whilst doing a brake job!


    Damping down the paintwork before hand can give you a bit of extra time to wash it off too.
    Another tip is not to lay the master cylinder cap top down either as fluid will work it's way past the diaphragm while you're bleeding the brakes then leak out after it's all back together.
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    • Post n°8

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    Post by liverpool_f_ Thu 04 Feb 2016, 9:09 pm

    Its nasty stuff. I am not so sure a rag over the vulnerable parts will protect them though. I put a rag around the master cylinder reservoir to catch drops and it really just aided in keeping the fluid in contact with the reservoir. That also does not look pretty.

    Can we just switch to dot 5? I had not considered the possibility of using brake fluid other than the recommended.
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    • Post n°9

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    Post by liverpool_f_ Thu 04 Feb 2016, 9:11 pm

    Also, my engine cover does actually look cleaner where the fluid spilt. I did consider it as a degreaser/super heavy duty paint stripper. Maybe that is a bit too caustic to be using elsewhere but my bike does have years of grime and neglect coating the engine...
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    • Post n°10

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    Post by Beresford Thu 04 Feb 2016, 10:37 pm

    Jameshambleton wrote:Protip, use dot5.1 and you won't get this problem! I typically only found out when I after I spilt dot4 all over my paint work too.
    Why is 5.1 OK? Is it designed not to eat paint? It's still a glycol ether compound like 3 and 4.
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    • Post n°11

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    Post by Jameshambleton Fri 05 Feb 2016, 9:14 am

    Beresford wrote:

    Jameshambleton wrote:Protip, use dot5.1 and you won't get this problem! I typically only found out when I after I spilt dot4 all over my paint work too.


    Why is 5.1 OK? Is it designed not to eat paint? It's still a glycol ether compound like 3 and 4.

    Sorry I meant dot5 as it's a silicone based fluid I believe.  scratch
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    • Post n°12

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by Beresford Fri 05 Feb 2016, 4:11 pm

    Ah. Here's what Wikipedia says about DOT5
    DOT 5 is silicone fluid and the above does not apply. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol-based fluid will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s. Silicone fluid is used extensively in cold climates, particularly in Russia and Finland.
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    • Post n°13

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    Post by Alvi Fri 05 Feb 2016, 9:55 pm

    I first used silicon fluid in a TR6 I rebuilt in the early 80's - it was still in there and working fine when I sold it 20 years later. I've used it in all my bikes ever since without any problems.
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    • Post n°14

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    Post by stormbringer Sun 07 Feb 2016, 8:43 am

    Beresford wrote:Ah. Here's what Wikipedia says about DOT5
    A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal.
    So, changing to the silicone based DOT5 on my CB would require me to take the entire brake system apart into its basic components, clean everything, dry it out and finally reassemble all parts using DOT5 as lubricant on seals etc.?

    Hmm... Now, there's a project Smile
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    • Post n°15

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    Post by Alvi Sun 07 Feb 2016, 7:15 pm

    I've usually changed to silicon fluid during a brake rebuild, so the master cylinder & caliper(s) have been cleaned, but I've just run a bit of silicon fluid down the hose(s).    On a couple of bikes I've just rebuilt the calipers & cleaned out the master cylinder as best I can. The label on my current fluid lists it's qualities as a higher boiling point, doesn't attack paintwork, doesn't absorb moisture & never needs changing, but these qualities will be compromised if mixed with glycol fluid. Other than that, it says it will mix & work with glycol fluid. I think I read somewhere that you could flush out the system with meths, but I'm not sure so don't do it without checking!
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    • Post n°16

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    Post by Llewelyn1965 Sun 07 Feb 2016, 10:56 pm

    What effect does it have on tyres? I just changed my front brake hose and fluid. Had a bit of a problem bleeding it and found out the pistons had seized. Had fluid drip over the tyre. I wiped it all off with wet wipes, but concerned it will affect the tyre.
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    • Post n°17

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    Post by wornsprokets Sun 07 Feb 2016, 11:26 pm

    No ive had brake fluid  over tyres no affect on them. Its only paint it affects.and it have to  be on paint a while.
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    • Post n°18

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    Post by eternally_troubled Mon 08 Feb 2016, 12:49 pm

    I reckon that if you wanted to change to silicone/synthetic fluid you could probably get away with flushing the system with the silicone fluid and throwing away what you flushed out, then refilling with new.

    The downside of 'never changing' the brake fluid is that the bleed nipple with seize up the one time you need to change it Wink
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    • Post n°19

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    Post by ashcroc Mon 08 Feb 2016, 1:06 pm

    I'm not sure that'd be a problem. Just because it never needs changing doesn't mean it wont require bleedeing from time to time. Air will find a way into the system no matter what fluid you have in there.
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    • Post n°20

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    Post by Beresford Mon 08 Feb 2016, 7:28 pm

    Currently available DOT 5.1 fluid is compatible with systems using older glycol fluids (DOT 3 & 4) It has extremely high performance and it is cheap. Silicone fluid doesn't perform as well in high temperatures  - it's more compressible giving a spongy brake feel, and it is 3 times the price. If you are likely to be messing around with the brake system, for example to overhaul calipers or change brakelines then silicone fluid doesn't make any economic sense.
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    • Post n°21

    Does brake fluid really eat through paint? Empty Re: Does brake fluid really eat through paint?

    Post by eternally_troubled Tue 09 Feb 2016, 1:44 pm

    Beresford wrote:Currently available DOT 5.1 fluid is compatible with systems using older glycol fluids (DOT 3 & 4) It has extremely high performance and it is cheap. Silicone fluid doesn't perform as well in high temperatures  - it's more compressible giving a spongy brake feel, and it is 3 times the price. If you are likely to be messing around with the brake system, for example to overhaul calipers or change brakelines then silicone fluid doesn't make any economic sense.




    I wasn't suggesting that you should change to it; just that you could, if you flushed enough of it through the system :)

    Anyway, as you say, I reckon that 5.1 is a better bet...  (says a man that is working his way through a big, well sealed tin of DOT 4 in the garage).
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