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1971 HLS30-14938 "Lily" build


Patcon

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  • 3 weeks later...

So I looked at the Maxima caliper I torn down a month or so ago. It apparently flash rusted in my shop when my dehumidifier quit at some point. I doubt it is salvageable...

So I am looking at options for how I'm going to deal with brakes. But I have a question. I was having trouble with the rear calipers not letting go all the way after being applied. I remember something about a check valve in the rear brake circuit to keep the shoes close to the drums. Is that correct? Where is it located? Is it the brass junction under the left rear of the car where the brake lines tee off? Is that why ZCardepot offers this?

https://zcardepot.com/collections/brakes/products/copy-of-metric-inverted-flare-t-fitting-m10-brake-line-connector#

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1 hour ago, Patcon said:

I remember something about a check valve in the rear brake circuit to keep the shoes close to the drums. Is that correct? Where is it located? Is it the brass junction under the left rear of the car where the brake lines tee off? Is that why ZCardepot offers this?

The check valve (if there is one) is built into the master cylinder. Not all master cylinders I've messed with have a check valve. Some of them have a "slows down the return valve", but it's not a full stop. Others do have a full stop below a certain pressure.

On the earlier 240Z, there are two "brass devices" under the right rear*. The first is a proportioning valve, and the second one is just a dumb "T" junction point. The feed comes from the master to the proportioning valve, and the output of the prop valve goes to the splitter "T".

The part that zcardepot sells is the dumb "T" splitter junction. However, neither of those brass devices contain a check valve.

 

*Closer to the right than the left.

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I am using a later master cylinder that I believe is a 280zx unit. So I shouldn't have the check valves then...

Still can't get the clutch to bleed. Not manually, not by leaving it open and not with the vacuum bleeder. I guess I will have to pull it out and diagnose it.

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10 hours ago, Patcon said:

I am using a later master cylinder that I believe is a 280zx unit. So I shouldn't have the check valves then...

Just because you are using a later master cylinder, I wouldn't assume it doesn't have check valves. In fact, I would stand by my original belief that there is one. Let me put it a different way...

Every master cylinder (70-83) I've messed with has some sort of check valve built into it. Some of them do more "checking" than others, but all of them had some sort of device inside that either stopped, or at least slowed down, the fluid back into the master.

Some of them had a "residual pressure" valve built into them that would hold some small amount of pressure (couple psi) in the lines, and some of them had a device that did not HOLD any pressure, but would allow much faster flow OUT of the master than back INTO the master.

Does that make sense?

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