6 hours ago, SteveJ said:

I think I found what you are referring to.

Here are most of the part numbers in that drawing:

No, I didn't see any mention of this in the 75, 76, or 78 FSM.

 

6 hours ago, Zed Head said:

Looks like they were only used for a short time period.

https://jdm-car-parts.com/products/water-inlet-lower-radiator-hose-rh-front-of-engine-datsun-280z-1975-5-1976?variant=27526042633

 

 

Thank you for the research - that is what I have, the t/stat housing with the nipple and the water inlet with same. The hard pipe was removed at some point, and they installed a long loop of heater hose, very ugly work. I'll have to rework it.

My AC is most definitely aftermarket - this is what I referred to regarding the line fittings - total crap 

Control panel

 

Edited April 1, 20231 yr by HusseinHolland

Definitely not a factory system. That pic spells it out. Vintage air is probably your easiest solution. Not easy but a solution. Your dashboard needs to come out as well. 

30 minutes ago, Yarb said:

Definitely not a factory system. That pic spells it out. Vintage air is probably your easiest solution. Not easy but a solution. Your dashboard needs to come out as well. 

I'll make my own lines. The dash will be coming out anyway. The main thing I have to figure out will be the controller. I'll make new lines & convert to Accumulator /Orifice tube, I did that with my X1/9

 

Edited April 1, 20231 yr by HusseinHolland

X1/9 with a Honda transplant! I bet that's pretty quick...

I wasn't there when they designed it, but my theory (based on my own experience*) is they found that the thermostat housing was completely dead-ended in 75 when they switched from carbs to the FI. You see... The carbs had water that ran through the intake manifolds and other locations depending on the year, but in 75 that all disappeared. In 75 if it weren't for that "bypass" the thermostat housing did not see any flow until the thermostat opened, other than the little hole in the thermostat.

I'm thinking the hole in the themostat wasn't enough flow and they noticed that the engine temp got hotter than desired before the thermostat opened (because it was sitting in a stagnant pool of cold water).

Then in 76 they piped it through the heating plate under the AAR.

I'm thinking 75 was the only year they needed to put in a bypass simply for the sake of a bypass,

 

* I'll go into it if anyone is curious, but not really necessary for this discussion.

@HusseinHolland, Yeah your car left the factory without air. Your HVAC system is all manual. All cables, no vacuum,

1 hour ago, Patcon said:

X1/9 with a Honda transplant! I bet that's pretty quick...

It is. 200WHP & only 2000lbs. JDM K24 with K20 head, 6 speed transaxle. I've had the car for around 16 years, I love it but I'm selling it to fund the Datsun, it doesn't need any more fiddling with 🙂

 

54 minutes ago, Captain Obvious said:

I wasn't there when they designed it, but my theory (based on my own experience*) is they found that the thermostat housing was completely dead-ended in 75 when they switched from carbs to the FI. You see... The carbs had water that ran through the intake manifolds and other locations depending on the year, but in 75 that all disappeared. In 75 if it weren't for that "bypass" the thermostat housing did not see any flow until the thermostat opened, other than the little hole in the thermostat.

I'm thinking the hole in the themostat wasn't enough flow and they noticed that the engine temp got hotter than desired before the thermostat opened (because it was sitting in a stagnant pool of cold water).

Then in 76 they piped it through the heating plate under the AAR.

I'm thinking 75 was the only year they needed to put in a bypass simply for the sake of a bypass,

 

* I'll go into it if anyone is curious, but not really necessary for this discussion.

So 76- on has an alternate bypass to keep the engine properly circulating coolant before the t/stat opens located where? I'm assuming the AAR = aux air valve, but I don't know the layout of the cooling system, and the FSM doesn't show much.

 

Edited April 1, 20231 yr by HusseinHolland

In 74, they bypassed the thermostat by pushing coolant through the carb system.

In 76, they bypassed the thermostat by pushing coolant through a little heating plate that lived under the AAR.

In 75, they did neither of those, so they bypassed the thermostat by putting that little bypass line in. It appears that coolant path in 75 didn't serve any other purpose other than to bypass the thermostat.

Here's a snippet from a 76 Service Bulletin where they discussed the changes from 75 to 76, Here's where they talked about adding that little heating plate under the AAR:

So in 76, they killed two birds with one stone... They fixed an issue with the AAR not operation correctly under all conditions, and they also fixed the issue of the stagnant coolant pool under the thermostat.

12 hours ago, Captain Obvious said:

In 74, they bypassed the thermostat by pushing coolant through the carb system.

In 76, they bypassed the thermostat by pushing coolant through a little heating plate that lived under the AAR.

In 75, they did neither of those, so they bypassed the thermostat by putting that little bypass line in. It appears that coolant path in 75 didn't serve any other purpose other than to bypass the thermostat.

Here's a snippet from a 76 Service Bulletin where they discussed the changes from 75 to 76, Here's where they talked about adding that little heating plate under the AAR:

So in 76, they killed two birds with one stone... They fixed an issue with the AAR not operation correctly under all conditions, and they also fixed the issue of the stagnant coolant pool under the thermostat.

Thank you for the information. Interesting that the AAR doesn't perform at optimum. I wonder what the issue is, I would assume idle related, since that's what would happen if the valve doesn't shut properly. Old Volvos & Fiats with D-Jet, K-jet & L-Jet that used a AAR bolted it to the head or to the block, which makes sense if you want it to properly close at normal operating temp.

Edited April 2, 20231 yr by HusseinHolland

I think they ran into a couple issues with the AAR operation. First issue is that on a very cold day, the cold air going through the AAR may have prevented the AAR from closing completely. In other words, the heating coil may have been overwhelmed by the cold air stream.

Second issue (and one that I have experienced myself) is the rapid cooling off of the AAR. Park the car and run into the store for a couple minutes... When you come out and start the car, the idle is bumped up again because the AAR cooled off. The thermal mass of the heating plate and the water slows that process down and prevents that.

That's my read.

On 7/3/2018 at 9:23 PM, Captain Obvious said:

Mike, Full disclosure,  I did not actually install that version in a car, but I did place the blower assembly and connecting duct into place to verify that there was no interference. So, while I cannot guarantee with absolute certainty that I did not overlook something, I have a very high degree of confidence that it fits fine.

Here's some pics of that version with the blower and duct in place. Top view:
http://www.240260280.com/co/au57-v/240-280/hvac/escortcore/P1100817.JPG

 

@Captain Obvious - I'm hoping you can clarify how the heater box unites with the AC section - the manual is very unclear to me  - does this entire box attach to the one in your picture where the foam seal is located on the left? I'm trying to figure out the layout before I take mine apart. Since it''s not factory AC, I'm wondering how the evap is mounted if the housing is not normally present on Non-AC cars. Can't seem to find a schematic that clarifies that.

 

 

Edited April 13, 20231 yr by HusseinHolland

On 3/31/2023 at 1:55 PM, Zed Head said:

I think that might be the purpose.  Not clear how many 280Z's or 260Z's or 240Z's had it or why nissan stopped using it.  I've seen it discussed before thoguh.

ZCD sells them and some people put a T in the return hose from the heater core.  https://zcardepot.com/products/coolant-hose-engine-bay-t-fitting-280z-280zx

Here's a good place to browse if you want to see what things are supposed to look like.  Sounds like you have an aftermarket AC system.

https://bringatrailer.com/listing/1975-datsun-280z-22-13/

I made a line to serve the purpose. Fiat EPDM hose at either fitting, then a Volvo shaped bleed hose with quick connect fittings to make it easy to service without messing with the end fittings