I apparently have some serious work to do on my brake hydraulics, and it would seem to involve the front proportioning valve warning switch, and/or  the rear  proportioning valve.   The rear is discussed in the FSM, and I'm about to get to work on that.  But as for the front warning switch unit, the manual is quite stern in demanding that you don't even try to fix it -  just get a new one.  Easy enough said, but unless I've been misled there aren't any new ones to be had.  Any thoughts on safety concerns on a DIY rebuild?

Thanks

 

Don't know if I should mention this but on a non Datsun car I had a long time ago I reused the original seals on a brake cylinder, making them work  by wrapping (string? wire?) around the metal seat where the seal went.  The idea was to expand it outwards to force the rubber to be in contact with the cylinder bore.  It worked but there are no standard ways of doing that I can imagine plus care would have to be used so that any material used could never work its way out of the seat area.

I believe Chas rebuilt one...

@EuroDat

4 hours ago, Richard McDonel said:

But as for the front warning switch unit, the manual is quite stern in demanding that you don't even try to fix it -  just get a new one.  Easy enough said, but unless I've been misled there aren't any new ones to be had.  Any thoughts on safety concerns on a DIY rebuild?

Thanks

Nissan do this a lot with brakes. They don't like spliting calipers either. The reason for replacing the switch instead of repairing it, is in the way the end fiting is designed. The end port has a fitting that is (lightly) press fitted into the end. See grwi8 post ID: 15, the red circle in the diagram shows the fitting. It can be hard to remove and get to seal again. You will need to remove it to get acces to the plunger. Mine has not leaked in 4 years.

I used the shank of a drill bit to fit in the hole and wobble it around and the fitting came loose. You might need heat to get it to come free. A simple hair dryer or heat gun should be enough. Heat the outside aluminium, not the steel fitting. 

Once that is out, its as simple as tapping the end on a block of wood until the plunger comes out. Don't forget to remove the switch first.

The o-rings are listed in post ID: 10. Make sure you use EPDM rubber.