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Just to clarify what SteveJ, S30Driver and ZedHead have said, you most likely have two issues: 1) your water control valve is seized; 2) with the result that your 'TEMP' control cable wire has bent at the point where it connects to the control lever. If you have an early car ('Series 1'), this is almost certainly what's happened. Some pix and comments follow: The control cable wire for the early Z's ('Series 1') was undersized (1.0mm dia) and therefore prone to bending if anything in the assembly got stuck or balky. In later versions ('Series 2', etc.) the cable diameter was increased to 1.2mm. The cable sheaths were upsized to match. The Series 2 design incorporated numerous other detail changes to the heater control system's mechanicals in an effort to make it more robust: revised lever frame, levers, and finish knobs; revised control cable wire ends (loop-over-peg). Lawn mower control cables can be a good replacement. Alternatively, try tempered-steel 'piano wire'. Otherwise, non-tempered wire from the hardware store will probably be ok, unless something gets stuck again and you try to operate the controls at sub-zero temps. Unfortunately, your water control valve and/or its actuator lever have probably seized. The probable reason is that the valve has a leaky seal. White stains on the outside of the heater plenum box are a clue. NAPA (but not Nissan) used to offer a replacement seal, but it's been NLA for years. So, if your water control valve is leaking you'll need to buy a complete new control valve. If you don't fix this problem, the old valve will leak coolant onto the floor whenever it's left in the 'COLD' position. Also, the actuator lever will probably start to stick again, too. I suspect that problems with the water control valve stem from PO's who run their cooling systems filled with straight tap water. A stuck water control valve responds nicely to an overnight soak in a de-liming product like 'C-L-R'. If the seal is ok, then you may be good to go. However, The older-design water control valves were said to also suffer from internal leakage, leading to a situation where the valve isn't able to fully block coolant flow even when it's set to the 'off' (cold) position. That certainly wouldn't help if you plan to drive a Series 1 car on hot summer days. Make sure you also free up the water control valve's actuator lever. Lubricate its pivot pin and grease the sliding surfaces. These are some pix that I took when rebuilding the Heater system for my Series 1 car: Below: Top side of Lever Assy Note: Control cable on the left side (TEMP) had been removed when this photo was taken) Below: Bottom side of Lever Assy (photo #1 of 2) Note: The bottom control lever (DEF/ROOM) and the associated left and right bellcrank plates had been removed before this photo was taken) Below: Bottom side of Lever Assy (photo #2 of 2) Note: In this photo, the DEF/ROOM control lever, bellcrank plates, and cables are in place. However, the control lever's centre actuating pin had snapped off so the bellcrank plates had nothing to engage with. Below: Water Control Valve, c/w actuator lever assy (actuator cable has been removed) Note: Control valve's actuator rod can be seen here. Actuator lever may need to be freed up and lubricated if it, too, has become frozen because of corrosion. Below: Water Control Valve's actuator lever assy Note stains. Presumably caused by leakage from the Water Control Valve. They look like calcium deposits. If they are, then my car's cooling system must have been filled with straight water at some point (probably during the time when it lived in New Mexico). Below: 'TEMP' actuator cable with bent wire (photo #1 of 2) Note: Here, the cable is fully extended and the bellcrank has been rotated about 45 degrees CW from its centred position. Below: 'TEMP' actuator cable with bent wire (photo #2 of 2) Note: Here, the cable is fully retracted, but the bellcrank has not been rotated CCW any further than its centred position.

The crusty one on the side is probably a switch. Nissan used a variety of combinations of switches over the years. Without the year of vehicle and engine a person can only guess.

As Steve said, it is connected to the watercock, as the slider is moved, it opens or closes the flow thru the heater core.

The one at 11 o'clock is the all important coolant temp sensor that tells the ecu how much fuel for the injectors. The big one at 2 o'clock is the thermotime switch which tells the cold start valve to add fuel and richen the mixture when ambient temps are low at startup. The single pin one at 6 o'clock is the temp sensor for the gauge in the cabin. You can easily test all except the themotime with a vom reading the resistance at a certain temp and referencing the factory shop manual guide.

When did you sell the 240z? This is a mortal sin for a forum member. Sent from my iPhone using Tapatalk

A fully charged 12v battery should be 12.7 - 12.8v If its 12.2, 3 or 4. The battery is low

That orange module is the temperature control switch for your A/C compressor. The temp silder lever on the HVAC control panel does one of two things: When you are in non-A/C mode, the temp lever controls the amount of water flowing through the water cokk. But when you are in A/C mode, the system automatically cuts off all water to the heater core using the vacuum controlled valve that lives near the water cokk. So when you're in A/C mode, no water flows through the core regardless of where the lever is. And then in that A/C mode, they instead use the slider lever to control the setpoint for that orange device. That orange cube is a temperature controlled switch with a sensor stuck in the evaporator coil. If the evaporator warms up enough, they turn the compressor on. And if the evaporator cools off enough, they cut off power to the compressor. Basically, they cycle the compressor and the duty cycle is dependent on the position of the temperature slider lever. TMI?

That's why I'm not married. I would have to have more than one.

What brand are your replacements? Klassic Fab makes some very nice floor pans. I only have experience with the 240 ones, but expect the 280 version to be excellent. https://kfvintagejdm.com/shop/datsun-280z/complete-right-side-floor-pan-datun-280z/

You can run the engine for a short while with the belts off. If the noise goes away it's something a belt was turning. Or the damper pulley (the drive pulley). AC idler pulley bearings are known to go bad and make noise.

It could be the water pump or the distributor button too. Get a short piece of garden hose to use a stethoscope and you can get really close with that.

It could be the watercock at the heater core. I sprayed mine down with silicone lubricant while I worked the slider back and forth. It moves smoothly now.

Hi Kats, I used to think I love them unrestored also, but it really messes with my OCD. Especially because on my white 71 the paint has flaked off in areas. I'm thinking I'll try and patch and touch it up, but leave it as rough and ready as I can, until the day I can't take it anymore and decide to refinish it properly. The hard part is knowing what parts to restore on it. For example do you replate hardware? Repaint the engine block? Air cleaner? Etc..? Reskin the dashboard?

Had to look at my casting numbers. HLS30-00026 has engine # L24-02338 casting # 9828A. HLS30-00027 has engine # L24-02162 casting # 9901D. 26th is a November car. 27th is an October car.

Yesterday, we inspected piston , this engine has pistons which have valve relief on top . I am wondering what kind of manufacture are they? The block has casting code 0211K , 1970 , February 11th K . 2146 and 2156 has the same date block . Edit : no, my 2156 has 0212I , one day behind of 2146 ! Kats IMG_6057.MOV FullSizeRender.MOV

You probably already know this, but the car in your pic above is a 77, not a 75. I don't know if the over rider bars are the same between those years. But if I had to guess..... I kinda doubt it?