chaseincats

Wow this is a lot more straightforward than I expected. I just took the below picture, you can see the defrost hose outlet (top) and the vent inlet (bottom) definitely missing its hose, with the heater core outlet vent open. Looks like I have a hose to buy, thanks all!

interesting, thanks. it sounds like the unplugged/potentially missing hose is the issue.

Interesting - in that case my 78 sends heat out of that defroster port regardless of if it is on heat or defrost. When I move the slider from recirc heat to defrost, it is definitely moving something though, which is strange.

Now hang on - mine is definitely not plugged in, I always thought that was where the hot air was supposed to come out when you turn on the heater! Where is the heat actually supposed to come out then??

It being unhooked would make sense since there was absolutely no air coming through. Is the area its connected to easy to access or does it require any disassembly to reach?

Hi all, I was driving my '78 yesterday and turned on the defrost. I noticed air is only coming out of the passenger side. I'm assuming that means the hose on the driver's side has a crack in it or something to that extent. I am assuming changing that hose is a absolute nightmare but wanted to check before I even opened the car door. TL;DR: Is changing the driver's side windshield defrost hose a nightmare/very involved?

FIXED; final update: The car is fixed and stops even better than before. Here is what was done: new hard line coming out of the master cylinder and tightened down within an inch of its life, new drums in the back since they were worn past Datsun's 'do not exceed' wear amount of 230mm. Mine were apparently 230.5 - the new drums have considerably more material on them at 227mm and adjusted well. The car stops on a dime, and the e-brake now only comes up a quarter of the way like @Zed Head noted. Like I said before, this is the first time I've been at a loss of ideas and given up on something which sucks, but I'm glad they were able to fix it and ended up being money well spent.

Update: I heard back from the brake shop - after adding the new hardline and taking it for a drive it is somehow still leaking but instead of a torrent of brake fluid now it’s wet/a couple of small drops. They are still working on it so it doesn’t leak at all but they are confused why this is still happening. This is with the original master now back in.

I literally woke up at 3am last night with the answer. Before I swapped the new master cylinder in, the rear brakes worked, driving it to the brake shop after that, the rear brakes did not grab using the pedal (but do with the hand brake). That means that the drums and shoes are fine, and its the hydraulics that are at issue. Years ago, I changed the master cylinder out and the one I changed it to had a shorter cavity for the pushrod to travel through. When I pressed the brake once, they car would stop, and the brakes would permanently lock until opened the bleeder screw on the master and let the pressure out. Since the rears worked with the old master, and now don't with the new, my theory is the new master I received has a cavity that is too long for the pushrod in the booster. I told the brake shop to install the old master (which still worked if you guys remember at the beginning of this saga) because that was the perfect length for the push-rod to actuate fully. The drums aren't the reason the brake hydraulics in the rear are no longer working essentially overnight - its the new master cylinder. I will report back when I hear from them.

Coincidentally I heard from him today. They made a replacement hard line which should take care of the fronts. Regarding the rear, he thinks the shoes aren't making enough contact with the drums because the drums are fairly worn. I noticed when I took them off that if you drag your finger from the inside of the drum outwards, there are very noticeable wear grooves on them and he thinks the brake shoes aren't making enough contact with the drums to properly stop the car. They want to replace the drums, but that shouldn't be the issue since I can stop the car with the emergency brake, right?

Right, but I thought the point of moving from master cylinders with 1 reservoir like cars of the 50s to master cylinders with dual reservoirs like we have today/in the Z is a safety thing where if one cylinder fails, the other will still work/help the car to stop. No? That's why I'm confused why even though one was not holding pressure/leaking, the reservoir for the rears held pressure but didn't stop the car.

Gotcha. It doesn't make sense though because the drum's brake cylinder (the cylindrical one closer to the front of the car) is full and bled. I thought the point of a dual cylinder master cylinder is that if one reservoir (in this case the disk's one - the rectangular reservoir closer to the driver's cabin) is empty, the other one should still let the drums work to stop the car. In this case, I had no brakes to any wheel.

That makes me feel better. His guess yesterday was the proportioning valve needing to be replaced but that wouldn't make sense since the car stopped perfectly before I changed the rear wheel cylinders/the front leak. Would the pedal not be firm if the proportioning valve needs to be replaced? My concern is the pedal feeling good once the fronts are bled despite the rears in-actuality not working. The parking brake handle did come up about halfway - definitely more than it was before I took the drums apart, but it did still stop the car/hold it. By half I mean from the center console to all the way up being 90 degrees - the handle stopped at around 45 degrees. When I was stopping the car with it, it definitely went up to two thirds of the way (60 degrees?), but never to 90. Regarding the brake pedal - I did notice when pressing the brake pedal at the VERY end of its travel, the brakes did BARELY seem to be barely slowing the car. I'm not sure if that helps, but slowing in that if I held the brake pedal, it would stop the car in a quarter mile or so. So basically when pressing the brake pedal all the way, the shoes moved enough to barely touch the drum, but that's it. Definitely not usable unlike stopping the car with the parking brake.

Thanks all! It shouldn’t be a clog because brake fluid comes out of the rear lines when the pedal is pressed and the bleeder screw is opened. This is the case on both sides. regarding adjusting the shoes after replacing the wheel cylinders - I thought the brakes auto adjust. I watched it do that when I pulled the e-brake a few times. EDIT: Out of curiosity, once he bleeds the front calipers, will the pedal feel solid despite the rears not working? I'm concerned that will happen and they will tell me the brakes are fixed when in reality, only the fronts are working.

Wow that’s pretty interesting - one if my seals must have been going but I don’t recall fluid levels changing between the reservoirs. That said, I suppose it’s a good thing I replaced the master even if it was my failed attempt at doing that to fix the leak where the master meets the line at port Y. The brake repairman is making a new metal line for that. However, the rear brakes don’t seem to be working at all now, (but fluid will come out of the rear wheel cylinders when the bleeder is open and the pedal is applied). The car will stop with the e-brake pulled but the pedal does basically nothing. I know in my triumph spitfire if a brake line loses pressure, the distribution block has a plunger that slides over and locks the leaking line so pressure no longer flows through it. In my case however, brake fluid does come out of the rear cylinders if I open the bleeder valve though. Could that be what is happening on this car? As of now, I have no brakes in the rear for some reason.

This is a huge help, thanks

Hi all, My left hood vent seems to have warped slightly and is no longer laying flat on the hood when bolted on. I noticed a few weeks ago that the rear 2 vent bolts were in, but the front of the vent had pulled its bolts off and was sticking up slightly. I found one on the floor and have no idea where I would get a replacement for the flat screw portion (that is glued to the underside of the vent). Do any of you know the name of that screw or if replacements even exist?

So I threw in the towel for the first time with this car and took it to a repair shop - kinda bummed I had to do that, but it's better than getting the brake fluid bath for the 15th time. Anyhow, I drove it down the street to the brake repair place (.5 miles away) at 10mph, with my hazards on, braking by modulating the e-brake, and got many of the 'I'm speeding past you in the left lane to show you I'm mad' folks driving by - and that's fine. I discovered that pressing the brake pedal now does absolutely nothing to stop the car even though the drum's reservoir is full and the master/drums are properly bled. The disc's reservoir (the rectangular reservoir closer to the cabin) is empty because that is the side of the cylinder that is leaking through the fitting. Do the drums not work if the disc's reservoir cup is empty? The brake repairman is curious if it could be the proportioning valve, but that wouldn't make sense to me since pressing the brake pedal while bleeding the rears shot brake fluid out. That said, that was when the disc's reservoir cup was full and bled.

This is perfect - I’ll pick this up and call it good!

I was just planning on chopping off the end and pressing the end into a flange since there is some slack I can pull the pipe up a bit so it fits.

There seems to be a noticeable burr on there which is probably the culprit (I don't understand how this existed for so long and didn't leak). Besides that burr if there is a small crack I think its time to just cut that end off and use a flange tool to create a new end. I'm seeing online the flange is a "double flare" fitting or a "bubble flare" fitting. Any idea which one it is and if you have a kit you recommend that would be able to produce this well?

so I swapped out the master last night and it’s unfortunately still leaking in the same spot so it has to be the line at this point like you were saying?

MAN remember the heady days of me celebrating that it was just a matter of screwing something in? Man those were the days. I took it out tonight and within about a minute or so of using the brake pedal it went pretty much straight to the floor now that it was stopping mass I guess. I headed back home and now there is fluid leaking out of the bottom of both where the front and rear brake lines screw in. Time to trash this master, right?

Update for all of you. We very may be in business here and you were all right - the hydraulic line was crooked/not fully seated and once I took it out and reseated it, the leak was gone. Again, I still don't understand how it didn't leak over the course of 6 years and thousands of miles, but I guess that was a good thing. I am going to bleed the brakes tomorrow just to be safe but I did bleed the master after all of this and the pedal feels good. Here are pictures of the line screwed in before, the flange/nut's condition when I took it out this evening, and how the cylinder looks now with the line in straight.

that makes sense