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Took the 899 out of storage the other day and noticed that the brake fluid in the front reservoir seemed like it had separated. Bike was kept in a temperature controlled storage unit through the winter and was started/run every other week. Does anyone know what it is? Should I be concerned?

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Flush it. Brake fluid shouldn’t separate. It’s either contaminated or old - so flush it. Good luck!


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Glycol-based DOT 3/4 brake fluid readily absorbs moisture from the air, but water and glycol are miscible (like engine coolant) and do not separate out. So it's not water contamination.

I suspect that the brake fluid has been changed from the recommended DOT 4 glycol-based to DOT 5 silicone-based fluid (or vice-versa) at some point and the system was incompletely disassembled and flushed.

Glycol and silicone do not mix. DOT 5 fluid should not be used in a Ducati that uses Brembo components.

This is what Brembo has to say:

BREMBO TECHNICAL NOTES

All Brembo braking products use natural-rubber base seals, and therefore are incompatible with DOT 5 silicone-based brake fluids. DOT 5 silicone-based fluids react with natural-rubber seals to swell them which can cause severe piston retraction problems.

There is no cure for problems caused by DOT 5 use other than complete seal replacement. Use only DOT 3 or 4 non-silicone type fluids … in your Brembo components.
(Yes, we know the cap on the Ducati rectangular master cylinders specifies “DOT 3–5 Fluids”, but please note: silicone-based DOT 5 fluids are not generally in use in Europe, but glycol-based DOT 5.1 fluids are. Hence, the DOT 5 cap designation.)

For best braking performance, we recommend changing brake fluid twice a year. If the machine is to be stored in a damp environment (over the winter, say) , we recommend installing fresh fluid before and after the storage period. At minimum service levels, glycol brake fluids must be completely changed at intervals not to exceed a period of 18 months.
 
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