Thread: DOT3 or DOT4 brake fluid

Brake fluids are normally backward compatible ie DOT 4 is suitable for DOT 3 etc. but not forward compatible. From memory the DOT rating is related to the fluid's boiling point.
Silicon brake fluid (DOT 5) is a different issue and isn't compatible with anything else.
Different manufacturers use different colours so the colour isn't important but the difference in viscosity is a worry.

If you've bled all of the air out of the system and the clutch slave cylinder is new then it may be a problem with the master cylinder.

Colin

and further to what Grommit has said, colour means nothing with brake fluids, all manufacturers/blenders use a different colour to each other within the same spec, it's only dye

That was what I had thought. Before I fitted the new slave I let the fluid drain out so when it was refilled it had all new fluid in it. It feels like my master cylinder plunger (innards) are stuck all the way in because the clutch is very light and obviously is not engaging (didn't start her and try but you know what a clutch should feel like and this ain't it!!!) I think if I took the pedal spring off the pedal would flop.

Also according to the book, the bleed valve should be at the top but mine was fitted (and working) with the valve at the bottom. I have fitted this way again but with the bleed screw pointing upwards (using the little Y piece) so it is actually above the inlet - would this still be ok? Or should I ditch the y junction altogether and try and fit it the other way round?)

Originally Posted by pfillery

That was what I had thought. Before I fitted the new slave I let the fluid drain out so when it was refilled it had all new fluid in it. It feels like my master cylinder plunger (innards) are stuck all the way in because the clutch is very light and obviously is not engaging (didn't start her and try but you know what a clutch should feel like and this ain't it!!!) I think if I took the pedal spring off the pedal would flop.

Also according to the book, the bleed valve should be at the top but mine was fitted (and working) with the valve at the bottom. I have fitted this way again but with the bleed screw pointing upwards (using the little Y piece) so it is actually above the inlet - would this still be ok? Or should I ditch the y junction altogether and try and fit it the other way round?)

I think that your problem is that you let ALL of the fluid out. Now, firstly you must bleed the master cyl, usually by cracking the pipe connection at the m/c. When you have fluid coming out of the connection, tighten it up and then try bleeding the slave cyl. If this does not work, maybe a new m/c is in order. Bob