Brake Master Cylinder Fluid Transfer

[600Z]

Hi guys,

 

I'm having an issue with the fluid transferring to the opposite reservoir (front to back) in the master cylinder.

 

I thought, ok it's passing within the master cylinder so I have installed a new 15/16" master cylinder thinking this will fix the issue........ nope

 

From the master cylinder the lines go to the pressure differential switch then to the proportional valve which it as you know backs off the rear brake pressure as more pressure is applied to prevent the rear from locking up during the weight transfer of the vehicle.

 

My question is if the proportional valve is leaking internally could this be the cause of the my problem, though I guess it could also be in the differential pressure switch. Has anyone had any issues with these?

 

Parts are hard to find but looking around a proportional valve from a 95 Mazda Miata physically looks the same though I'm sure the spring rate etc would be different but with testing and changing springs it might work, any thoughts? (See picture of Mazda unit)

 

Justin.

[dat2kman]

Forget the Miata one, it will be setup for their rear discs, and car fore/aft weight balance.

It will be reasonably close though, are you running rear discs?

If not, ie stock rear, I have a spare prop valve. Can pack n post.

PM me, if you cant find one near to you.

[Blue Z]

Hi Justin,

 

I had the exactly the same issue, just pull out the pressure differential switch and replace O rings. The O rings in mine had split and caused this fluid pumping issue.

 

Good luck,

 

Blue Z

[Linton]

yeah mine did that after I fitted a new master cyl, I am on my second new master cyl, Strangely it stopped with the second master cyl. but I will check the o ring thingy now as well.

 

thanks bluez

[600Z]

Hi Blue Z,

 

Thanks for that I'll check that one out too, that's the first one with the switch, not the proportional valve isn't it?

 

And there just o-rings in there no cups?

 

 

Justin

[Blue Z]

Hi Justin,

 

Yes one with switch, yes O rings only from memory.

[600Z]

Update guys on this, Blue Z was spot on the mark (thanks) it was the differential pressure switch.

 

One o-ring was split and the other had a nick in it so I measured them up and got some EPDM o-rings which are compatible with brake fluid and now working a treat.

 

I also removed the bias proportional valve block from the firewall and installed a Wilwood adjustable unit, so much better as now the rear disc's are getting the extra pressure they require.

 

Cheers,

Justin.