This is leaking on my 85 300zx z31 and I cant find it on any diagrams online or any other threads any help would be appreciated!

 

that is your hot coolant control valve. why don't you download the fsm and do a little work for yourself

 

Welcome to ZDriver!

That gadget controls the hot antifreeze/water mix circulating through your in-dash heater core so you can get heated air from your dash vents. Typically it's open or closed (summer, no need) and is operated by your vacuum lines which take directions from the climate control switches and buttons on your dash.

You can download a factory service manual and parts fiches and other great docs at XenonZ31 Reference. They're freebies assembled by Xenon who deserve an award for that.

I don't know whether a new valve is available from Nissan (tell them the part number from the fiche) but I would guess not. If it is the valve that needs replacing, (check your hoses for leaks first - those valves rarely break down - and Nissan OEM parts ain't cheap) I would go to car-parts.com, sort the search results by distance from my zip code and hope to find a Z31 (it died way too soon) on a recycling yard close to me. Then I would drive there and harvest all the parts I want from that beautiful, tragic corpse. Saves money and keeps the planet greener!

 

Thanks for the explaination on that man it helped a lot. The only salvage yards around here are LKQ and Cash And Carry and neither one of those have any z31's. But hopefully. I can figure out why its still overheating with the info you gave me on the part and with the fsm download. I just took the thermostat out and its still overheating so I'm gonna move on from there to the heatercore system. My carpet is dry as a bone on the passengers side so I'm not sure if it will be that either

 

If you are overheating and not leaking anywhere - and you replaced your thermostat with an OEM-equal one - you will need to check out your water pump. It's under the timing belt cover. While you are in there, may as well install a new timing belt, new tensioners, etc.

The Z31 water pump rarely fails so look for other causes - and make water pump replacement your last resort... Can't think of another reason for your symptoms. Radiator clog? I've heard about that but never seen it. You need to restore free flow of coolant to the system. Overheating is dangerous for your engine. Keep your eye on that temp gauge.

 

Alright Ill have to look into that, how would I go about checking the water pump to figure rather or not its good or bad? And what do you mean by restoring free flow of coolant? Do you mean just refilling it with antifreeze and water or something else? Btw preciate the helpful tips and info once again!

 

OK, your engine cooling system is pretty simple. The water pump is run by a belt powered by your main crank. (Water pump is under the timing belt cover so is fairly hard to get to. Time and labor in that.) When the engine is running, the crank turns and powers (spins) the water pump which pushes antifreeze/water mix up and through the motor where the mix picks up heat from the motor, heats up, is circulated back to the radiator where the radiator fan and cool air push the temperature back down - and the mix keeps circulating that way. That circulation has to be non-stop with no interruption or the engine overheats (bad deal).

First, make sure you have no system leaks. You can tell by parking on a dry spot somewhere as the car heats up and starts to overheat. Look for wet spots on the ground. If leaking, gotta be fixed. (If it's a hose, not difficult, not much labor, parts are cheap)

If you are still overheating and have no leaks, it must be a pretty basic problem. Either the mix is not circulating right so it is not being cooled at the radiator (bad water pump or a flow blockage somewhere)- or your thermostat, which controls the amount of hot mix circulating to the radiator, isn't operating right (bad thermostat).

So, thermostats are cheap and fairly easy to replace. Start there. Get an OEM/equivalent thermostat and replace it. If overheating continues, check for blockage, probably at the radiator. (Z31s tend to run at a rock-steady temperature - with the gauge needle pointing almost exactly at the F symbol right in the middle of the gauge and never moving up or down, even a little. When it moves higher, park the Z and let it cool.)

You can check for mix flow by cooling the motor down completely. Open the radiator cap and fill with mix to just below the bottom of the opening so you can look in and see the surface of the mix. Leave the cap off, start the engine and let it sit there idling. Add mix if the level drops (air leaving the system). OK to raise your RPMs at the accelerator/throttle while you do this. As the mix heats up, the thermostat will open and eventually you can see the mix flowing in the radiator by looking down into it with the cap off. You will see it flowing by, right to left, I think. But it will move. You can tell it's flowing through the radiator.

Turn off engine before normal running temp is reached or radiator will boil over. If you see no mix flow as engine heats up, your water pump is bad (or your thermostat is bad) - or you have a blockage. So start there with this test. If you have flow in the radiator, water pump is probably OK. If you have flow and already replaced the thermostat, you have a blockage somewhere. Even if you have some flow visible, the radiator could still be partially blocked - so eventually you will overheat. A good radiator place knows how to pressure flush the blockage out - or you can replace the radiator with new aftermarket or recycled one. Your call there. But you gotta run at the right temp. Essential repair here.

Please let us know what you come up with. Everybody learns that way! Thanks.