Clutch fluid topping and changing

[nick]

Is it OK to mix fluid types in the clutch reservoir? I know this is not a good idea with the brakes. I don't know what is in there now and it needs topping. If mixing is not allowed, should I drain the old and then add the new? I would hate to go through a bleeding process if I don't have to. I read in previous posts that it is a real pain.
And what about regular fluid changes like with the brake fluid. Is water in the clutch fluid a problem as it is with the brakes?


nick
'79 TR7

[Spectatohead]

Nick, the same rules apply to the clutch hydraulics as the brakes. I've never had any trouble bleeding the clutch. It only has the one circuit and one line from the master to the slave. On the other hand I've had a hell of a time getting all of the air out of the line going to the rear brakes.

Jim Clark
'80 TR8
'97 Maxima 5spd

[windy one]

I dont like to mix fluid 'brands' but will if need-be. I dont usually mix fluid types either unless I have to. DOT-3 and DOT-4 mix together fine. And in a pinch, you can use 5 with 3 or 4 but Id suggest changing it out asap when possible. Now, Im sure this will cause a stir amongst others here who will say not to mix 3/4 with 5. But when I used to race Buell motorcycles, we would purposly mix 3/4 and 5 for better feel and responce on the track. I used to know the full answer (on mixing on the bike) but its been yearrrrrrrs now and I dont really recall.

As far as changing regularly, depends on the amout of driving I did. My truck I do once a year regardless. My Bike I do three times a year. My 7 I do twice a year, with fresh fluid from an unopened container. That is, brake And clutch fluid on each vehicle.


Johnny

[Gubi]

Yeah, stir indeed. Mixing 3/4 with 5 is a really, really bad idea - they are completely different chemicals and are incompatible. Considering how easy standard brake fluid is to find I'd never even consider it.

Water in the clutch fluid is less of a problem than the brakes as you won't ever boil your clutch fluid, but it's still an issue from potential rust in the lines/cylinders perspective. Personally I just replace it whenever I do the brakes.

Mixing various brands of 3/4 isn't an issue, so you can top up the clutch with fresh fluid no problem (assuming you know the stuff in there is glycol-based and not DOT 5 silicone). You can add DOT 3 to DOT 4 but you'll lose the higher boiling point benefits of the DOT 4 (again, really an issue for the brakes rather than the clutch) so best to just stick with DOT 4 for everything: it's easy enough to find and doesn't cost much more.

I always flush with fresh DOT 4 fluid for both brakes and clutch every two years. Any leftover brake fluid gets tightly sealed and I'll use it for those two years to top up the system if needed (my logic: the stuff in the bottle isn't absorbing any more moisture than the stuff in the car. Probably less, actually, given the MC cap is vented). After two years any remaining fluid gets thrown out and the system gets flushed again.



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Tom
'79 TR7
'87 Alfa 75
'91 Alfa Spider