Look at this picture..Is this too high

[sblake01]

I have a stock radiator in my 78, fan shroud, OEM thermostat, etc. and my temp never goes above the degree icon next to the 'F' even on the hottest SoCal days with the AC on.

[DaveN]

That temp gauge is definitely too high. Assuming its not just a bad gauge or temperature sending unit, have you cleaned all the dirt and bug carcasses out of the air side of the radiator core? ....checked the water pump & belt? checked the temperature sensitive clutch in the fan? ....checked for a collapsing lower radiator hose?

Does the car have A/C installed? The condenser in early Z A/C units cut fresh air flow enough to cause overheating problems at low (or no) speed. Part of the problem was hot air recirculation -- air took a short, low resistance flow path from the back of the radiator, underneath it, and up the front to be pulled through again. A sealing panel from the front valance to the bottom of the radiator crossmember blocks that path. You can also fab a foam or rubber lip seal for the gap between the crossmember and the hood. BRE style "chin spooks" may still make thhe lower seal. The one I bought in '71 did, and it really helped (in Albuquerque). A fan shroud also helps in stop and go driving, but causes a flow restriction itself at highways speeds. I needed all three in ABQ summers, but was able to ditch all but the chin spook when I moved to Raleigh, NC. Other owners got good cooling with the lower valance seal and one or two thermostat controlled electric fans replacing the stock fan.

Re the thermostat -- get the largest, best streamlined water passage you can find, and run a 180 or 192 opening temperature. Either in good condition will be fully open 20-25 degrees above its rated temperature, and from there to the boil over point the opening temperature makes no difference. A 192 minimizes thermal expansion stresses on the head and gasket by keeping the coolant operating in a narrower temperature range, but could make hot weather stalling (gas boiling in the SU's) worse.

Are you running stock SU's? If so avoid a 160 thermostat or change the carb jetting to compensate. A lower coolant temperature leans the mixture a little, especially in the front carb, and the stock 73 (and 72 round top) needles are already so lean that additional leaning is likely to burn exhaust valves.

[Bulldog Z]

Hey Mally 002,

I have a 3 row radiator made by CSF and it works just great. My temp guage never gets above halfway even on 100 plus south ga days. CSF will ship the radiator right to your door. Mine was around $189. Try their site www.csfimports.com. They also have tech guys that can help as well. Hope this helps.

Brad

[KDMatt]

I'm going to sound off in agreeance that the temp gauge is reading FAR too high.

Half way in between 120 and 250 is 185, so it should be very close to the middle with a 180 degree thermostat. That reading you have right there looks pretty close to 215 or 220.

If you say it goes back down at speed, then I would also say you could try a fan shroud. It might certainly help get more airflow at lower speeds.

ALSO, while we're at it, is your fan clutch doing it's job? When your engine gets hot, you should hear the loud whirring of the engine fan as it speeds up to cool things down faster.

Still... way too hot for a 76 degree day (hotter days are ahead!). Aftermarket thermostat sounds like the most likely culprit so far to me as well.

Or... you could just forget about it and move to Alaska

[justaZcarguy]

Nice call on the fan clutch, that is what I was going to suggest...

Sounds like the Z is cooling down with forced air-flow and heating up with no flow.

And KD, if you are going hide in a tree, at least paint 'er cammo!

Just kidding, I know of your tree curse...

Check the fan clutch is my vote.

~Brian

[240ZMan]

Ditto on the fan clutch. I had the same symptoms. In my case it was a little deceptive in that it did engage A LITTLE, just not enough to cool at idle for a long light on a warm day. New clutch solved it.

[deadflo]

I had the same exact issue, it was an aftermarket thermostat, the OEM solved the issue, I would try that first before the other stuff.

[mally002]

Many thanks for the input.....quick question though. If I go electric on the fan, which is about $125.00, would this eliminate the fan clutch? In other words if your going electric do you remove your old clutch, plastic blades, and shroud? A new fan clutch alone is $89.00, so why not go electric...(Can you tell I'm not much of a mechanic)

Also in regards to some of the questions asked.

* I do have a/c but never turn it on

* I am running stock SU's, and was going to order the 170 Tstat OEM

* The 2 row radiator seems to be fine, no dirt, bugs etc....The 240 is very, very clean and "refurbished" so I hate to replace the radiator if the 2 row will work with a new OEM tstat and electric fan, or new clutch.

Thanks again

[CANDYBLUE2+2]

Mally, I still have the old style 2 row radiator. I removed the fan/clutch completely and installed a single electric fan. The Nissan thermostat is a must, just dump the aftermarket crap, the savings are not worth the headaches. With the electric fan in place, the fan shroud is no longer needed. The car never gets above the half way mark, it now has more power without the fan clutch set-up, and is noteably, much quiter under the hood.

So many have done similar set ups with varying results, but I haven't personnaly heard anyone say that they would ever change back, so somethings gotta be right here.

Just my 2 cents, John

[Caen Fred]

I have the same trouble, may I run without thermostat for a while... things are longer to get when you want OEM around here?

[sblake01]

I also have an electric fan on the front of the a/c condenser that only runs when the a/c is on. I don't know how much it helps w/overall cooling but it really helps in keeping the a/c vent temps down at lower speeds.

[KDMatt]

And KD, if you are going hide in a tree, at least paint 'er cammo!

Just kidding, I know of your tree curse...

Ugh... it's not a curse... just two back-to-back coincidences... yes... that's all

Anyway, back on topic here, going electric might help your problem, especially if you're not noticing any kind of additional "whirring" at lower speeds/higher temps. A new OEM fan clutch will run you upwards of $80.

My only opinion on the electric fan is on electric current, the Z alternator is, subjectively, pretty weak, in my opinion, for additional electrical goodies. If you're not going to be placing any other loads on the system (foglights, CD Player, amp, etc. etc.) then you'll probably be okay...

I'm just, personally, very nervous and superstitious when it comes to electrical stuff... and until I pop in a high-output alternator I probably won't ever feel safe having more than two or three draws at once. :tapemouth