mixing brake fluid
- Thread starter Shel_B
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DOT3/DOT4/DOT5.1 are all miscible, so long as DOT3 is the minimum required for your system you will be fine. I'd be more worried about needing to top up the brake system in the first place if you're not servicing it, and if you are servicing it you'd be best just to flush the system if you're that concerned.
I think Japanese manufacturers generally specify DOT 3. If you don't want to bleed the system, I recommend syringing out as much as you reasonably can from the master cylinder and refilling with DOT 3.
I've heard that mixing DOT 3 and 4 lowers the boiling point to below that of either.
I've heard that mixing DOT 3 and 4 lowers the boiling point to below that of either.
Shel_B
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Perhaps I should have explained the situation more fully.
I'll be getting a brake job sometime this year and the brake fluid, which is less than three years old and looks pretty clean, is down a fair amount due to pad wear. I don't want to flush the system only to be doing the repair in a few months, so I just want to top off the reservoir.
I'll use a syringe to draw out some more fluid and refresh with DOT 3 as that's most likely what's in the system now.
There is no reason to top off the brake fluid. It is normal for the fluid level to drop due to pad wear.
Agreed. Just a waste of fluid.
The manual specs FMVSS No.116 DOT 3 or SAE J1703. You can add DOT4 to that if you like. I'd stick with DOT3 as it is not a sports car or load hauler. Toyota doesn't feel it needs a higher boiling point fluid, so DOT3 will just absorb water slower and give longer service interval. YMMV.
The system is designed so that the reservoir holds more fluid than will be drained out due to pad wear. As others have stated, there is no need to top it off, nor to siphon any off.
There is seldom any need to siphon any off unless it is very old and there is sediment, then it is good to try to stir the sediment up and draw out the reservoir instead of flushing through the system, but then you have to be thorough, once you have gotten sediment loose it is worse than if it stayed stuck to the walls of the reservoir.
You can siphon off, not a big loss since brake fluid is inexpensive, but then there's still a mix in it and most effective would still be to do the following which takes care of that without the extra step. It is unlikely you have excessive sediment in a properly maintained 2011 vehicle. You'd see the sludge if you do.
When it come time to flush the old fluid out, keep an eye on the reservoir, flush out the first brake line (wheel) till the reservoir is almost empty but never completely empty. Top off reservoir with fresh fluid. Continue to flush the same line to get fresh fluid in it. Next proceed to flush the other lines. Keep topping off the reservoir with fresh fluid as you go along.
The system is designed so that the reservoir holds more fluid than will be drained out due to pad wear. As others have stated, there is no need to top it off, nor to siphon any off.
There is seldom any need to siphon any off unless it is very old and there is sediment, then it is good to try to stir the sediment up and draw out the reservoir instead of flushing through the system, but then you have to be thorough, once you have gotten sediment loose it is worse than if it stayed stuck to the walls of the reservoir.
You can siphon off, not a big loss since brake fluid is inexpensive, but then there's still a mix in it and most effective would still be to do the following which takes care of that without the extra step. It is unlikely you have excessive sediment in a properly maintained 2011 vehicle. You'd see the sludge if you do.
When it come time to flush the old fluid out, keep an eye on the reservoir, flush out the first brake line (wheel) till the reservoir is almost empty but never completely empty. Top off reservoir with fresh fluid. Continue to flush the same line to get fresh fluid in it. Next proceed to flush the other lines. Keep topping off the reservoir with fresh fluid as you go along.
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