Flush hydraulic brake system

[Snails]

I'm going to bite the bullet and strip my GP over the winter (will it ever get back together!). So as part of that I want to change the type of hydraulic fluid from the corrosive type to the non corrosive (dot 4 to 5?)

I know you should not mix these so I assume I need to flush my old system? If so how and with what?

[dennis]

Good move to DOT5, had this in mine for 9 years with no problems before some one comes on here and condems it.

[hendy]

Use dot 5.1. You can mix it with anything. I've done it loads of times.

[Muppet]

Dot 5 is silicone based and is more paint friendly than other brake fluids as it doesn't strip paint with contact so it has its advantages
Dot 5.1 will strip paint and is not a silicone based brake fluid

[Snails]

Thanks for the clarification. Any idea on how I would clean out the old fluid so its not contaminated?

[Monty]

I would bleed it so the reservoir is low but not empty then top up with fresh and bleed it through after topping up 2 or 3 times you can be sure its all new in the system. you may be able to disconnect the fitting and blow it out with an air line but not worth the effort IMO

[Snails]

Thanks Monty, I hate bleeding the brakes but I suppose it will be good practice for me for when I reassemble!

[Monty]

I use a 6 or 7 foot long bit of fish tank air tube, you can pump it through and see any air even better if you can get a different colour fluid you can look for the change in colour as you push it up the transparent tube. If its getting full you can lock of the bleed nipple and drain the tube and start again. I wouldn't split any couplings. How are you doing with the Lou

[Snails]

Thanks I will bear that in mind. Need to get my head around how it all works as not done it for ages. Normally I have a bleeding kit so will think about whether I can incorporate your suggestion...

The Lui is up and running and for once seems problem free. Only another 40 miles and ts run in!