Datsun Roadster Forum-311s.org

Yes, The radiator cap is blank and the recovery tank cap is pressurized.
I believe I have the stock recovery tank cap and it is marked A9 which
I think means 9 lbs pressure. The spring feels about that much compared to a 15 lb cap.

Ted.

Hey Nissanman,

Assuming your temperature gauge is correct (do you have access to one of those non-contact digital thermometers to verify it?), here are some things to think about...

Before you look at swapping caps, or other solutions, are you sure that your cooling system is working as it should?

When you say that it's running hot, is that when sitting still (stopped in traffic for example) or when cruising at a decent speed?

If the temperature is ok when cruising, then your issue is likely related to lack of airflow - do you have a shroud fitted around the fan? (Did the 1500 have a shroud? The 1600/2000's certainly do)

If the temperature is high all of the time, it's likely a coolant flow issue. Or if you've hotted up your engine maybe your radiator doesn't have the capacity to cool it.

Using plain water, the 7psi cap should allow the temperature to get up to around 112C before it boils. A 15psi cap will raise the boiling temp to around 121C. If you're using a Glycol mix the boiling temperatures will be even higher. Considering the thermostat temp is around 92C, even the 7psi cap and plain water will give you a fair bit of margin before it boils.

My roadster has never given me temperature troubles, even on the 45C days that we get in Melbourne in summer, but I did spend many years trying to sort out cooling dramas on my Torana so I know how much fun it can be!

There's the rub.
I do not know if the gauge is reading correctly.
I already have a CHT digital readout but unfortunately it has a short lead and isn't located where I would like.
It rarely goes over 190F.
Once I get my spark plug CHT readout finished I will be reading a better location with respect to the gauge sender.
See details a few posts back.
All new stock engine, radiator and fan shroud fitted

At this point, I suspect the gauge adjustment but until I get another reference for the operating temperature I can't prove it.
Thanks for your suggestions

On my 65 1500 (which has a different radiator than the 63-64 1500s), I had a similar issue. After trying every combination of repair, I relocated the temperature sensor to the upper radiator hose to measure the water temperature. Turns out on my car, the stock location of the sensor, was being heated by the exhaust manifold causing inaccurate temperature readings. Once the sensor was relocation, the temperatures reading went back to the normal range.

I'd be careful about that location.
It is after the thermostat and therefore doesn't read ENGINE coolant temperature.
Ideally, the Temperature gauge should read what the engine is experiencing, i.e. prior to the thermostat

datsun65 wrote:On my 65 1500 (which has a different radiator than the 63-64 1500s), I had a similar issue. After trying every combination of repair, I relocated the temperature sensor to the upper radiator hose to measure the water temperature. Turns out on my car, the stock location of the sensor, was being heated by the exhaust manifold causing inaccurate temperature readings. Once the sensor was relocation, the temperatures reading went back to the normal range.

I had that issue with a mechanical gauge but not the stock electric sensor.

Well, I have done some research re temps. of the engine at various locations using my digital display and K-type thermocouple thingy and, as I suspected, the cooling system is fine
Spark plug #1 and #4 read within 5degC of each other at ~80degC.
The water bypass hose connection at the head reads in the high 70s.
And my industrial temperature switch for the electric thermo-fan operates at 88degC and cuts out at 68degC, fine for a bit of insurance.
All in all, it's just the gauge that needs to be re-calibrated to a realistic reading.

However, I went ahead and built a coolant recovery tank since I don't enjoy the idea of the system weeing coolant out when it gets hot.
I used some plastic pipe with a threaded connector cemented to it for a short neck radiator cap fitting: - Here it is located beneath the radiator bottom tank, hanging on some custom aluminium brackets which are bolted to the front chassis rail.
The radiator now has a blanking cap fitted to it and the recovery tank has a short neck 7psi/50KpA pressure cap.
The radiator overflow tube now has a pressure hose running to a brass connector in the base of the recovery tank and a drain valve as well.
The tank has an overflow tube and a hose that exits where the original did

The capacity of the tank is about 1.5L but it is made that long so I could make use of some existing threaded holes in the chassis rail to mount it.

Sprayed with satin black it is virtually invisible apart from the nice new shiny pressure cap.
Works fine, I just need to seal a few little leaks here and there but it has passed the 62mph test on our local expressway

I have also flushed the system with an alkaline cleaner and re-filled with a 70/30% mixture of softened water and Nissan Long Life Coolant.

Now to remove my temp. gauge and find the adjustment mechanism.
I'm told by an ex gauge repairer that there are access holes in the gauge case to a pair of adjustment wheels, for low and high settings.
Another little jobby

Now that is one very stealthy solution! Environmentally responsible too!

You probably have it covered Nissanman, sounds like you do but just in case this very topic is on my to-do list so I had researched it a little.
Sadly the folder I keep information in to leave room in my brain for other stuff I have left at work (I hope).

Anyway this is one of the articles I had found. http://www.mgb-stuff.org.uk/fuel.htm it relates to a fuel gauge and also another "car" but not that different, the gauge that is. For the purposes of understanding the principle of operation.

You could probably stick the sender in a pot on the stove and monitor the temp and resistance; saves running the car hot to get the high point gauge setting right.

Finally being a 1500 I'm lead to believe (could be wrong) the temp sender works the other way to the 1600 regarding temp V resistance so if it was not grounding properly would it read high, low or not at all? on the 1600 a short would read full scale and eventually upset the gauge!

Like your tank by the way

Took the tank out to attend to a few leaks so I was able to get some better pics. of the finished item: - The tank is 65mm diameter and 400mm long.
The capacity is approx. 1.487L.

Well, it was a good idea at the time
It got too hot in the kitchen for this little black tank: - Blew the neck clean off and distorted the tank like a banana
Clearly not up to the task.
So it's back to the design department.

Decided to go for this little jobby: -



http://www.ebay.com.au/itm/121406025990 ... 1497.l2648

It should fit nicely in about the same location but needs a pair of mounting brackets dropped vertically from the lower radiator panel support bar.
Couldn't make it for the price, so it's out with the old and in with the new

Well, I did try

Well, my upgraded you beaut pressurised coolant recovery tank is all done and works like a charm To get it in there, the tank just fits between the front sway bar and the steering cross rod
Once in there it has plenty of space to be positioned in the centre of the radiator. Held in place with two angle brackets dropped vertically from the lower radiator brace and two strips angled back to the front chassis rail. Haven't painted it yet, may never bother.

Nissanman,
Where did you get the correct looking 65 blanking radiator cap?
The blanking caps on the later years are smaller diameter and do not fit.
I guess the pressure part could be cut off and a rubber gasket made, but I hate to resort to that.

Blanking cap: -
CPC http://www.cpcauto.com.au/radiator_caps.aspx P/N 2001

Tridon http://www.tridon.com.au/catalogues/ P/N TRC10

Quite a selection.
Thanks for the lead.