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I have one (1) 'Intake Manifold Thermostat' in my parts bin (PN 14100-E8850). As you probably know, this valve is NLA from Nissan and appears to be NLA from all the Z specialty suppliers too. Its job is to control the flow of coolant through the intake manifold heating cavities (which also duct out to the carb bodies for 1972-73 models). I expect that it's arranged to work the opposite of the regular coolant thermostat: i.e. it operates open when cold, then closes off flow once the coolant heats up). According to the Parts Manual, they were fitted to the Z engines right up until July 1973. I want to fit my parts bin unit to my '70 (which arrived with the manifold thermostat missing), but only if it's working properly. I just tried a dunk test in boiling water and it wouldn't close, so I assume that it's jammed in the neutral/open position because of the usual chalky crud that can build up in a poorly-maintained cooling system (my unit hasn't been installed in an operating vehicle since 1980, so it hasn't been 'exercised' for a l-o-o-n-g time) Does anyone have any experience with fixing these little thermostatic valves? I can't find any mention of it in either the Z FSM or the L24 Engine FSM -- not even a note on a diagram to indicate that it even exists. Q1: I'm thinking of soaking it in CLR, on the assumption that it's mineral deposits from tap water that are causing the problem. Has anyone tried this? Q2: What's the correct temp. at which it should start to close? And how long should it take for it to cycle from fully open to fully closed? Q3: Do I have the operating logic correct? (i.e. normally open, then closed when hot). Is it designed to fully close, or just partially close? Q4: There's a tiny phillips-head screw with an equally tiny lock nut on the tip of the internal centre shaft. Has anyone tried to take one apart to assist in cleaning up the moving parts? Q5: Does anyone know of a source for these (either NOS or used)? Any guidance welcomed.