oldschool2

Thermostat Bypass Hose for the 280ZX is a 3/8".

Looks like this is referred to as a Thermostat Bypass Hose. Anyone know "for certain" what the "inner diameter" (ID) is? Thanks

What is the correct name for the small hose that attaches to the thermostat housing?

The water hose is not plugged. The water travels from the engine "heater hose out outlet" to the "heater hose water return inlet" on the engine. The net effect is that the heater is bypassed. The reason for the above is / was to avoid having to dig into the dash area to replace the worn-out heater hose that traveled from the engine "out" to heater assembly (under the dash). If the hose was simply plugged there would be no water (coolant) circulation in the engine. Not a good thing!

The attached pic shows how I by-passed my broken heater hose set-up. May not be the problem here, but if so the pic shows how. Of course the heater will not work as noted in the pic (heater is basically disconnected).

While searching for the cause of excessive fuel tank pressure, I was able to get rid of "all" pressure in my 1982 280zx non-turbo. One hot Vegas day I was at wide-open-throttle (WOT), and had a total "flame-out." The car apparently lost fuel to the injectors and died. Eventually, I found that the problem with excessive fuel pressure was an in-line non-functional fuel-check-valve. I replaced the fuel check valve, put everything back to stock configuration, and had no more flame-outs.

There is a Fuel Vent/Vapor Check Valve between the Fuel Tank and the Carbon Canister. Yours may have been removed. This check valve controls the Fuel Tank Pressure (pressure in the tank). If you have a check valve it may be a two or three prone configuration. Later 280ZX cars seem to have the two prong (in out only).

Regarding heater hose: Generally, to the right rear protion of the 280zx engine are two fittings (in and out) for hot water to enter/exit the heater assembly. I would expect that yours are capped or may be already looped as noted above to bypass the heater. Possibly there is a leak in one of the two provisions.

My leak was from a heater hose failure. If yours is bad you can put a new hose on the engine to heater outlet and loop it to the heater to engine intake. You will have no heater but eliminate the hassel of digging into dash. I think it is a 5/8" hose, not sure. Same works for a heater core problem.

This is an FYI only posting. These solenoids are getting to be hard to find. Part Number is: 31941-X0103 Mine was seeping trans fluid for years. I finally got a new Nissan part solenoid as pictured.

This car (see image) was in a van outside my condo in Vegas from the SEMA show today.

See my post titled: 280ZX Fuel Tank Vacuum and Fuel Check Valve (last two posts). Currently on page three of these S130 Series posts. The Tank fitting is for the Fuel Tank Vapor to feed into the charcoal canister. The picture on my noted post shows a modified set-up. The round object to the right of the picture is actually a check valve that normally is under the car near the fuel pump (on a non-turbo). Note the larger hose. It is from the fuel tank. Basically I just inserted the check valve between the fuel tank VAPOR hose and the canister (relocated it) from under the car to the engine compartment. Blocking the fuel vapor hose will cause extreme pressure build-up in your fuel tank in hot weather. Maybe it has been modified at some other point leading from the fuel tank. Probably a good ideal to trace the hose back to see if it feeds into the fuel tank.

Ok, All is well. TESTS: 1. Direct hook-up between fuel tank and Charcoal Canister (no check valves), and new fuel cap with built-in Vac Vent resulted in zero pressure in fuel tank. As expected/hoped for. 2. I relocated the "new" Vac Relief/Fuel Check Valve PN 17330-P7103 to the Charcoal Canister area. Keeping the new Vac Relief Valve Fuel Cap in place. Results are that the fuel tank now has "moderate pressure" in 95 degree weather. I think may car actually uses the PN 17330-P7900 (smaller valve), but "if it works do not fit it" is the current plan I am on. I suspect that the difference in the two check valves is that the larger check valve has a Vac Relief "air in" tube, and the smaller PN 17330-P7900 does not. I think that I have set-up a double Vac Relief Valve system where the Fuel Cap and the Check Valve have Vac reliel capabilities.

I have removed the mystery part. The part I have/had on my 1982 280zx date of mfg May 1982 is a PN 17330-P7900. This is the part that susposedly went on earlier models according to Courtesy Nissan in Texas. The attached pic shows the PN 17330-P7103 on the left and the PN 17330-P7900 on the right. Rather than wasting time trying to determine which is intended for my cars configuration, I will simply do a few days of trial and error. 1. I will run the car with a bypass (of any check valve) and hook-up (Vapor Line) directly from the fuel tank to the Charcoal Canister. 2. Next I will install the larger PN 17330-P7103 to see what happens. I know the PN 17330-P7900 does not work so it is "out of the equasion." I will post an update in a few days.

I have added a new Thermo-Temp Switch and Cold Start Valve. I have also started cycling the fuel pump 3 times (Ignition on/off 2 times and on the third cycle I turn ignition switch all the way) as noted somewhere in regards to hot restarts. All I know is that I can now restart my car when it is Hot enough to trigger the Aux Fan. also, can not realistically think of a better plan for the Aux Fan. I will wrap it in double sided foil and that is the end of this project. Thanks for all the inputs. Oldschool2 Las Vegas

NOTE: The part I am confused about is pictured in POST #3 above. It seems that my "hot-restart-problem" is not directly caused by pressure in my fuel tank, and related comments in this thread. I still have the problem when I vent to the atmosphere by using a fuel cap with a hole in it. Heat is indeed causing my problems with a hot restart, but that's another thread. I will probably just attempt to do a "bypass" of whatever is in the place where the subject "Fuel Tank Vacuum and Check Valve" is currently located. I'm thinking of using the new part I have in the bypass. I really would like to know what that part is in the pic I attached above (2 post up). I live in a Condo with no car repairs allowed. I have to go to a local speed shop to get things done. Kinda slows the process.

There is no part as pictured above (sketch) on my car. There is an unknown part in the vacinity of where the subject Valve goes , but I am unable to identify it. I took my car (1982 280ZX, Non-Turbo, Auto Trans to the only Zcar garage I know of in Las Vegas. They said they were to busy to look under the car (real class act). They said the part I had in hand was for a California Emissions car only. I have a Federal Emissions car. The part I have been referring to, and that is on page 59 of the Haynes repair Manual, and susposedly under the car, appears to be the same as is on the "carbon Canister." I have no clue as to what is under my car. I am trying to attach a pic. Summary: My car has no cover plate with a Valve/fuel check part as noted in the repair manual page 59. Any ideals?

Correct! I mentioned the Timer in my first post. I guess I had Heat Soak of the brain. I removed the top fan ducting piece and it is apparent that the potential for "heat trapping" is indeed present in the Fuel Injector "valley." I suspect that the fan ducting that covers the injector area actually adds to the trapping of hot air when the fan is not running (99.9 percent of the time).

Thanks for the input: Your input provides useful information. To sum-up the gathered information in addition to your above information > The sensor is in the thermostat housing and has a single wire leading out that goes into a wiring bundle. At the fan motor end there are 2 wires (1 from sensor)connecting to the fan motor. I think 1 wire is a ground. = 2 wires total.

I have finally received a new "Fuel Tank Vac and Fuel Check Valve" (one part). I will post the results good/bad/no change, as they may be in a week or so.

Well, LOL all you want! Facts are that heat soak is a real and common problem with the Zcars. Nissan added the Aux Fan for a reason. The repair manual even mentions Vapor Lock. Yes I have read all the comments about Vapor Lock not affecting FI cars. Call it Vapor Lock or Heat Soak the symptoms are the same. There is no telling what mods may have been made to your car. If it is stock then you are lucky. I am trying to get info for a mod I plan to make to the Aux Fan. The Aux Fan does not help with heat soak in my experience. That is why I am thinking of making mods to the Aux Fan. Also, I see no problem with trying to understand how a system works.

Thanks for the question: Yes I do! Reason; 115 degree days (in the shade). 150+ degree pavement. Black car. Engine bay over 200 degrees. All this equals heat soak. Although it is doubtful that the Aux Fan will help in OEM form, I am interested in modifying the Aux Fan to draw in cool air from the front of the car (maybe). Before I do anything I am trying to understand how the Aux Fan works in stock configuration. Further research indicates that the fan is triggered by a single wire sensor coming from the thermostat housing (near thermo time switch). I see a single wire in the vacinity of the thermostat housing, but am not sure as it does not look green as I have read in some posts.

Anyone have actual photos or good diagrams of the correct wiring connections for a Non-Turbo (NA) 280zx FI Auxiliary Cooling Fan? Also, what tells the fan to turn on at 216 degrees? Is the fan motor connected to a temp sensor, or is there a built-in temp sensor within the fan motor mechanism (BiMetal) ? The Haynes Manual is not very helpful. I guess the timer assy is under the interior glove box. Does the "extension duct" that pulls cooler (?) air from below help. I have read that the Turbo ZX cars had the extender duct that attached to the fan intake. My fan motor does not have the extended ducting, therefore the question. Thanks

Thanks for the input: Fuel Pressure was checked. My then new FP Regulator was not holding pressure to specs, so a second FP Regulator was purchased. Now FP is held to specs. No problems with the radiator or water temp.. Timing has not been checked specifically. When I get the new Valve Assy/Fuel Check part I will have the timing checked. I do know that the car runs without a "hickup." Car is running hot only in the sence that it is totally heat soaked. Also, this car is painted BLACK.

Thanks for your input. The hole in the gas cap is a "quick-fix." I am eliminating potential problem areas one at a time. I have not received the Valve Assy-Fuel check part yet. When I have the new Valve Assy part, I will put my NEW vac vented gas cap back on, and take it from there. To Date I have installed: New Fuel Pump, Fuel Damper, Fuel Filters, Fuel Pressure Reg. (holds pressure to specs), Fuel Injectors, Air Regulator (idle was off), 02 Sensor, Crankcase hose (the big one), Vac hoses, Fuel Tank inspected 2 times, no rust or crud. Heat Shields are in place. The FI Aux fan works to specs. New Spark Plugs and wires, MSD Coil (Mild Version). Car runs excellect. Problems begin at around 95 degrees. Generally, the fuel tank has moderate pressure (with vac vented cap in place). Then when super hot days come along the pressure goes out of wac. I have experimented with vent to atmosphere instead of Carbon Canister (no apparent affect). I am not sure about the Fuel Return hose and the vac to distributor hose in regards to their affect on (if any) engine restart. Not sure of elevation affects. Las Vegas 2000+ feet, Phoenix 1000+ feet, Los Angeles average 300 feet. Just tossed this in to point out that there are many variables to be considered. My supercharged 1996 Nissan Maxima (Stillen Kit) would not run in Colorado at 6000 feet. That was fixed with a oxygen Sensor adjustment.