1" Master Cylinder Installation Help

[Whittie]

Hi All,

 

I picked up a new Nissan (Tokico) 1" master cylinder, allegedly from a Nissan Patrol. Pic:

 

 

When I went to install it on the weekend and I was bleeding fluid through it by hand I noticed that I had to plug the front port and apply a lot of pressure to get any fluid to come out of the rear port.

 

Now, I have an issue with the current 15/16" Master Cylinder in that the rear brakes drag. I have read a bit about a "Proportioning Valve" but searches can't find anything conclusive only some more mystery about some valve that maintains pressure in the system to the rear brakes for the drum brakes. I initially thought I had an issue with the calipers so I bought replacement ones but I still have the same problem so I'm beginning to believe this alleged myth.

 

I have Holden 2pot front brakes and R31 skyline rear disc brakes. This is a HUGE bit of kit, fronts equivalent to 4-6pot brakes for any other manufacturer.

 

I believe this new 1" master cylinder is internally regulated and I would like to remove this and also the valve maintaining (I think) pressure on the rear brakes. Can someone with experience let me know what is involved in swapping this master cylinder in so that it all works properly? I would like to do this once and not have to come back to it again.

 

Thanks!

Edited May 18, 2010 by Whittie

[cockerstar]

Can you describe your rear brakes "dragging" in some more detail?

 

Do they always drag, even when not braking, or do they lock up before the fronts do while braking?

[johnc]

Hi All,

 

I picked up a new Nissan (Tokico) 1" master cylinder, allegedly from a Nissan Patrol. Pic:

 

 

When I went to install it on the weekend and I was bleeding fluid through it by hand I noticed that I had to plug the front port and apply a lot of pressure to get any fluid to come out of the rear port.

 

Now, I have an issue with the current 15/16" Master Cylinder in that the rear brakes drag. I have read a bit about a "Proportioning Valve" but searches can't find anything conclusive only some more mystery about some valve that maintains pressure in the system to the rear brakes for the drum brakes. I initially thought I had an issue with the calipers so I bought replacement ones but I still have the same problem so I'm beginning to believe this alleged myth.

 

I have Holden 2pot front brakes and R31 skyline rear disc brakes. This is a HUGE bit of kit, fronts equivalent to 4-6pot brakes for any other manufacturer.

 

I believe this new 1" master cylinder is internally regulated and I would like to remove this and also the valve maintaining (I think) pressure on the rear brakes. Can someone with experience let me know what is involved in swapping this master cylinder in so that it all works properly? I would like to do this once and not have to come back to it again.

 

Thanks!

 

No modern brake system that I know of maintains pressure to the rear brakes. Your issue might be the pushrod length from the booster to the MC. Generally it needs to be adjusted to make sure the MC pistons are fully retracted when there's no pressure on the brake pedal. Search this site using "pushrod length."

[Whittie]

Can you describe your rear brakes "dragging" in some more detail?

 

Do they always drag, even when not braking, or do they lock up before the fronts do while braking?

 

They drag. There is pressure being applied to the rear brakes when there is no pressure on the brake peddle or hand brake.

 

They also seem to do it intermittently of late. Sometimes they will be on slightly, other times they will not.

 

They lock up after the front brakes so it's not a biasing issue, they just drag.

[johnc]

They drag. There is pressure being applied to the rear brakes when there is no pressure on the brake peddle or hand brake.

 

 

Then there's something wrong. Again, check the pushrod length. It might need to be shortened just a tiny bit.

[Whittie]

Then there's something wrong. Again, check the pushrod length. It might need to be shortened just a tiny bit.

 

Cheers John.

 

Looks like I need a new brake booster anyways cause I can't be bothered dealing with modifying this one to fit the 1" master cylinder that has mounting screws horizontally instead of vertically. I'll be sure to check it out though either way.