So I've been searching and reading and learning what I can, but I'm a bit overwhelmed by everything and need to ask for clarification. My '72 is my first experience with a dual reservoir brake system and I'm not sure what's what.

First off, what is the device that's mounted in the engine bay below the MC? Pictures below.

http://s132.photobucket.com/albums/q27/AwwsChwA/z%20parts/?action=view&current=MC2.jpg

http://s132.photobucket.com/albums/q27/AwwsChwA/z%20parts/?action=view&current=MC1.jpg

I understand it's got a switch in it that triggers a trouble light in the event of line pressure loss, but specifically what is this little machine and what else, if anything, does it do for the braking system? Is is a metering valve? Is it something else? Is it correctly connected to the MC?

I understand the overall function of hydraulic brakes, worked on lots of them over the years, but I'm unsure of this lil bugger and I think it's best to ask before I go diving into things with wrenches a'flyin'. Thanks, everyone.

The larger resevoir is the front brakes, the smaller is for the rears.

Yourpressure warning block apears to be hooked up correctly.

Follow the large resvoirs line down to the block, it's line above and beside it should go to the front brakes.

Same for the rear brakes resevoir.

It's just basically there to allow a pressure sensor to be hooked up inline with both front and rear brakes, and warn you of low pressure in the system. It also acts as a divider for the front calipers.

^Thanks, that helps a lot! I traced the lines coming from the MC and then from the splitter below.

The larger reservoir feeds down to the bottom connection of the front (closer to the radiator) three connections on the lower switch. The remaining two of those three come out the top and front of the switch and those trace out to the front calipers.

The smaller reservoir feeds down to the bottom connection of the rear (closer to the firewall) two connections on the lower switch. The remaining line goes along the firewall and under the transmission tunnel to the rear brakes and presumably splits further down.

This sounds like exactly what you described, so that helps the understanding factor quite a bit. Is there any kind of active shut-off built into the low line pressure warning light? I remember seeing a thread about having zero fluid flow through the rear brakes after improper bleeding as a result of that switch tripping some kind of shut-off. Was I reading something that pertained to a different model?

Thanks again for the assistance, I hate not understanding this stuff.

That's why you ask questions. To learn, and to keep me on my toes.

There's no shut off in the Z system. It either works, or it don't. All the switch will do it yell at you, telling you to fix it. But that's it.

The rears are split via a brass block, after the proportioning valve. Other models have a proportioning valve on the firewall.

Dave

If you don't already have one, get a copy of the Factory Service Manual (FSM) for your year. The FSM (not cheap third-party books) has good explanations of all the systems in the car, how and why they work.

Glad I can help keep you on your toes, Zs Thanks again for the explanations.

Arne, I've actually been hunting for one. Is there a particular publisher or aftermarket supplier that's recommended?

Look again, I said "Factory", not third-party. You want a real Nissan manual.

You should check with Mike McGinnis at Banzai Motorworks, they regularly have FSM's for sale.

zspert@olg.com

http://www.zzxdatsun.com/

Thanks, guys! Arne, I completely understand that you meant factory when you said it, I asked about aftermarket publishers becuz the 3-volume factory service manual I still own for my late '91 Honda CRX Si (I still miss that lil car) was genuine Honda information but was a reprint through a third party. Even the covers are authentic. I still have the factory service books for each vehicle I've owned and worked on. It's a short list thus far, but I keep them as souvenirs

Just to get you by until you find a paper version of the FSM:

http://www.xenons30.com/reference.html

Click on 72 and save to your desktop.

John

Freaking killer, thanks Johnny! I've already emailed Bonzai Motorworks, so hopefully progress can be made quickly.

Your welcome. Nice thing about the pdf is that you can print out the section you need, grease it up good then throw it away. Same thing is true for the club microfiche CD.

It would be nice to find the 70 and 71 FSM in this format.

John