Wrong brake fluid advice please

lemonenema

cleaned and bled my 2nd bikes brakes as I reaslied one piston in each had seized, not a problem ive done this before, calipers off, pistons out and cleaned. All working again nicely and new pads in, lovely.

Then I realise I put mineral oil in what had previously had dot 4......
I know that using dot 4 in mineral oil brakes (shimano) will kill the seals and stop the brakes from working, but what about the other way around, have I made a big boob or will it be ok with mineral oil?
If so is it just the piston seals or are there others?

veronese68

There are seals at both ends. Manufacturers would probably say it’s scrap due to product liability, but I have no idea as I have not done it myself. You could have a go yourself, just be very careful with the brakes for a while afterwards.
Take it apart as much as you can, clean it and then flush it through with the right fluid, you might get away with it. Also do it now, get the wrong fluid out ASAP.

lemonenema

I had thought of changing the fluid again but its been in there overnight now and I applied plenty around the pistons so I think its too late. Im probably going to do a test ride around the village and see if they are fubar, thankfully its my 2nd bike which has clarks brakes not the main bike with Hopes.

steve_sordy

lemonenema wrote:

I had thought of changing the fluid again but its been in there overnight now and I applied plenty around the pistons so I think its too late. Im probably going to do a test ride around the village and see if they are fubar, thankfully its my 2nd bike which has clarks brakes not the main bike with Hopes.

The longer you leave it the worse it will become. If you flush it out now, you may get away with it. If you leave it, you will never know when it will finally fail! :shock:

lemonenema

as an update, yep theyre fubar, didnt even get 12h on and the back brake is seized.
No matter! they were only cheap brakes, im just annoyed i put new pads in them which are now of no use to me.

david7m

lemonenema wrote:

as an update, yep theyre fubar, didnt even get 12h on and the back brake is seized.
No matter! they were only cheap brakes, im just annoyed i put new pads in them which are now of no use to me.

The wrong fluid has done that so fast? I thought it would take weeks.

steve_sordy

Many thanks lemonenema, we've all learned something from your mistake.

gezebo

That’s interesting that they’ve seized. I’d have thought that a seal would have perished (if that) and you’d have had leakage first. Who would have thought that a glycol based fluid would have caused that.

steve_sordy

Maybe the seals swelled up and jammed the pistons.

trekvet

Steve is probably right. What has probably happened is the mineral oil has swollen the rubber seals throughout, get a new set of seals and use the correct fluid is what I would do.

Alejandrosdog

whilst youre messing about I would be tempted to do a belt and braces approach and replace hoses as well. are your levers knackered as well? can they be rebuilt?

veronese68

lemonenema wrote:

...thankfully its my 2nd bike which has clarks brakes not the main bike with Hopes.

Very thankfully. I'm all for fixing things if possible but in this case if seals are available they'll probably cost nearly as much as the brakes, put it down to experience and buy new brakes.

lemonenema

already done! got some barely used Sram level brakes on ebay, already sitting here waiting to be fitted.

veronese68

Excellent, just remember SRAM use DOT fluid

lemonenema

vegetable oil, right ill remember
no no dot oil, right.....

It wasnt the remembering that was the problem, it was the picking up the wrong container issue.
All part of the fun DIY process