i agree the little 1200 radiators have big problems in the heat. As i live up in the hott North Queensland area, mine used to heat up very quick. even when i reconditioned the old datto 1200 raidator it didnt last long, even a different thermostat didnt help much. so eventually went to the larger Ca18det and thermo fan. And since then no probs at all

I would fit a shroud if you can fit one, but a thermo fan will help. I have used two thermos on my 1000 raditaor to help her out, and that more or less fixed it. One blows on one side, the other sucks. I cant fit a shround in there, so thats the best it gets.

Another thing, the engine was also pinging in the heat ... I had the timing right on the edge (no pinging), but yesterday it pinged taking off, and at full throttle at mid-rpms. Controlling the heat would be better than retarding the timing I should think.

I would go the higher capaciity Gemini radiator or N12 pulsar alloy radiator for the extra capacity. An excellent condtion used one is around $50AUD
Another thing, I wouldnt worry for street use about the temp getting to that level...when its off the clock for an extended period that would be a concern. Also you can get different temp ratings on your thermostats as well. I would recommend a 185 degree F original Nissan theromstat. These are used in race applications.

I find that B120Dat's suggestion of installing a CA18DET to cure overheating problems is a good idea
But seriously. A dirty radiator just doesn't work.

Many 1200 radiators just need re-coring, after years of neglect and mineral rich water.

I agree with the "off the clock" = worry. The guage should read in the middle. Otherwise you have a stuck thermostat, and you will suffer premature engine wear from the "cooler" working conditions.

The shroud is a good idea, but many radiators and blocks/heads are choked up with 30 years of oxide buildup.

Chris

I had exactly the same problem with my 1200GX on the highway.
In summer I cannot drive faster than 100kmh then it starts to rise steadily.
Summers get also here about 32 to 34 degrees celsius.
It also rises and falls when driving on the highway uphill and then downhill.
I took it to a radiator shop and the guy said the radiator is not made for our high temperatures.
I am going to put in a different core that has triple row of tubes and more tubes per inch and also more fins between the tubes.
They said this is enough for a A15 so it will work for my A12.
Try to put in a new termostat.
I did it and it helped a little but not quite enough.
Good luck

Just get an electric fan and wire it to a switch on the dash. Worked for me

so the comon thread i'm hearing from all these comments is that there are several solutions:

More airflow (additional fan, or maybe fan shroud)
or
Clean radiator (or new core)
or
Larger radiator (either slightly larger, or more rows or cores, or much bigger)

It would help if you could bring the variables under control. A baseline is to ensure that the car is up to stock specs.
For the exercise, i will assume that you do not have dragging brakes, half flat tyres, & that the engine is in good condition & is correctly tuned.

With that out of the way, you can check that the core isn't full of bugs, that the fins are not bent or there isn't anything else obstructing the airflow.

Is the cooling system filled with nice clean coolant? [not water, propper coolant]
Are the internal tubes blocked at all? The hot day can raise the temp enough to fully open the thermostat & the resulting higher coolant flow can stir up sediment in the block that then starts to block up the radiator core.

I'm guessing that you are running an original 30+ year old original radiator. If so, then it doesn't take Einstein to figure out that this radiator can't shed as much heat as the engine produces on a 95 degree day at the speed that you drive.
The most cost effective fix is to simply slow down. Engine produces less heat & radiator copes better. Honest

For a real fix the radiator must be able to shed more heat than the engine can make, & to achieve this you can.

A. Clean & service the cooling system, including professional, tanks off, radiator clean out.

B. Replace the radiator core with stock, or preferably, a heavy duty replacement while the block gets a good flush.

C. Replace the whole radiator with a newer, larger unit, either used or new, & get all the crud out of the block. I usually do this by removing the core plugs & digging it out. Make sure that you use a filter to prevent rubbish from the block blocking up the new core. Most use a sock stuffed up the top hose fitting, & held in place by the top hose & clamp. It works quite well.

The electric fan options do not address the real problem, that being the radiators ability to handle the heat load. You can blow air through it with the propwash from a DC3, but if the radiator isn't up to the task, then it needs fixing.

Chris
P.S. I personally went for option B. using a heavy duty triple row core in both my 200B [810] & for my 1000 coupe. The extra cost over a stock core was amazingly low, & i drive in near century heat, with the aircon on,... no sweat.

Whats the best way to wire up a thermo fan? i don't have the standard one anymore, (won't fit) and this one is a blow through one.
do i just put it straight to the ignition so that it is on whenever the engine is running???

whats with that brake light below the charge light??? When does that come on???
(when u go over 100mph? )

2 things not yet covered:

1. water pump cavitation, at higher speeds 120km/h I found the standard pump cavitating. I fitted a larger pulley to slow it down.

2. Total timing not being enough: if it is not advanced enough you retain too much heat in the combustion chamber.

These 2 items may help if you are JUST on the edge, don't expect anything amazing. These fixes have worked for me when they changed the speed limit from 100 to 110 and the datsun couldn't handle it.

Interesting that you say to little advance can create heat . I have the spark knocked back to reduce pinging on my 1200, and the harder I drive it the hotter it gets. If this is the cause , I may have to run AVgas all the time, ($10000 fine for using it on the street) or make a smaller pulley to lower the boost, (nooooooooooo) My radiater is out of a two litre cortina. And although it isn't mint , I feel it should have enough cooling ability/

Quote:Well, is three out four OK? I do in fact have one dragging rear brake. I guess I should replace it.

Here's one DD, do you have the stock 4spd and stock sized tires? 60mph = just over 4000 rpm? Maybe this is a little too fast for a stock 1200 since 94mph @6500 is full blast for stock.
I've noticed that around 4500 rpm all the temps go up to the next level. The car won't overheat but...it gets close.
I turn on the heater and roll down the windows.

piss the engine fan off and run a 12" thermo fan with a switch on the dash my 1200 ute had an A15 and this setup had no worries keeping it cool when it rose to half way switch it on 2 mins later it was back down to in between the C and half way.
Cheers Luke

Yes, I have the stock four-speed and 155-12 tires. But consider, when sold new, the speed limit was 65mpg in this country ... so the car is designed for this speed (at least).

After taking another look, i figure that you should be looking for a gas station about now anyway. Yes, i know, it's a Datsun 1200, so there's probably another 200 miles of economy driving left in the tank, but hey, the engine needs a little rest, so a pitstop isn't such a bad idea.