This is a normal typical Datsun temperature. Within the "satisfactory" range per the owner's manual.



Here is my Datsun from a 100+ degree day (over 38C), pulling a hill to pass a truck. I was doing 4250 RPM.


It still was not overheating even at this extreme normal range. Any hotter though and it would start to overheat (push water out the overflow tube). So it's right on the ragged edge between running hot and overheating.

If your Datsun normally is around the 1/2 mark, but gets to this temp when going hard, it's time to get a radiator that provides more cooling. Either a new 1200 radiator or a larger radiator will provide more cooling. You can fit a used B210/B310 wider radiator which has substantially more cooling and was designed for A14/A15 engines.

edit: Changed the word "normal" to "typical".

Above half is not normal, except on a very hot summer day.

A radiator may look perfect on the outside and be completely blocked on the inside.

Any radiator shop can remove the tanks, poke rods down all of the tubes so they flow right.
New core is only needed when the tubes are so corroded that they have holes in them.

To bring back the Datsun reliability, you should get the radiator looked at.

If they quote more than $200 to recondition it, look to get a new one.

My 1200 radiators have run about here (on hot days) since 1982.


Another reason I call it "normal", because one needn't worry about it. I realize many people do worry about it, but they needn't.

Of course if it goes to the H mark more than once, I'd start worrying about that. One time hitting the H may mean it needs water added (especially if it occurs a day after changing the coolant).

The other reason is that the Datsun 1200 Owner's Manual says anything in middle range is "satisfactory":



Quote:

maybe a different coolant might help. Whats the fins like on the radiator, and when was it last flushed out. should never be that hot unless there is something wrong. My old sunny after doing more then 750000kms was still running on the original radiator and never got that high even when driving up north in australia were temps are much higher then that. Or your thermostat might be goneski. Just a few things i can think of that might help

YES, something is wrong here. It is very close to overheating.



Yes, Sunny came with a much larger radiator and pretty much stayed rock-solid temp.

Now this is pretty typical for a Datsun 1200. Sure it is not perfect but that's how they were.


Datsun 1200s came with a marginal radiator (as did many 1970s vehicles) and the temp moved around on hot days, under heavy load etc.. Even with good coolant, good fins, good thermostat, good flow, etc. Don't believe me? Read your Datsun 1200 owner's manual.

Oh, the reason mine was close to overheating is I put an A14 in it, and it runs up to the H mark when ALL these occur:
* running high speed (110 kph or higher)
* running close to full throttle
* on a hot day
* up a hill

The radiator that is in there now NEEDS TO BE REPLACED to work reliably in all conditions with the A14. It's not that it needs a rod-out, or new coolant, or fins replaced. It is just too small for an engine considerably in excess of 69 HP.

But good point about fin damage or internal blockage. If that's the case, the radiator needs to come out to fix it. So repair or replacement, it needs to come out.

If the coolant is old or contaminated it should be changed. But I've never seen it solve a case where the temp runs close to the H. I've replaced coolant and done back-flush on lots of Datsuns. It certainly can help a little.

Thermostat is unlikely to cause this problem (steady middle temperature except when under heavy load).

Dave, when our coupe was stock with a brand new radiator it would do fine in 110 degree stop and go traffic but the instant the motor went above 4000 RPM's (freeway) the needle would shoot up to the outer edge of the range. ( Due note on one road trip I ended up running the heater) It wouldn't over heat but came very close. The bigger radiator solved the issue. The only time I've had problems since is when the radiator started to plug up. The 210 radiator does OK but I'd go bigger / 3 core if you plan on any road trips to the desert again.

Tom

Thanks Tom. That matches what the owner's manual says, and my own experince, that the temperature can move around in the middle zone even when the radiator is in perfect shape.

I have a 3-row 1200 radiator I will try out. But I might go the B310 extra large radiator (A14 w/AC).

I have a Datsun 1200 pickup, the engine runs ok. of late i have noticed that when on climbing late, the speed would reduce and the temperature gauge would go upwards to the high level. The coolant is just full but opening the radiator cap , i would notice hover heating, could this be faulty water pump or radiator. the radiator had a small leak and i used STOP LEAK from a local shop. could this also cause blockage to my radiator ? no more leaks on the radiator.

Thanks

Luak

Opening the radiator cap when hot will cause boilover even when everything is in excellent condition.

Stop leak, when used per directions, will not cause blockage of radiator



See Temperature