Small coolant leak the cause of overheating?

[Sergio146]

Does anyone know if a small coolant leak on the heater control valve can cause an overheating condition? The truck in question is a 1980 datsun 720 l20b 4x4. Thermostat was changed already as well as the water pump.

[bottomwatcher]

How long ago on the thermostat? I have gotten lots of bad thermostats out of the box in the past, even the more expensive ones.

[Sergio146]

It was a cheap motored now that I remember being a cheap $5 one.

[Sergio146]

*motorad

[bottomwatcher]

That would be my guess you have a bad thermostat. Just looked and you are in a cool climate. That being said I am having an issue where mine doesn't let the truck warm up and I bought a genuine nissan for $30+ dollars. 

[datzenmike]

A leak won't cause over heating until the coolant level drops drastically and it can't circulate.

 

Never cheap out on thermostats. Spend $8-$10 and get a good one. A cheap thermostat can cause a severe overheating problem leading to a warped head and blown head gasket. Is that worth it?

 

 

If the heater is leaking have you by passed it by joining the two heater hoses???? If you have make sure that one of the hoses is plugged so there is no circulation.

 

Now... define overheating. Where on the gauge does the needle read?

 

 

[Sergio146]

Overheating is 1/4 under the H mark

[bottomwatcher]

This is what I bought. Only $23 must have been thinking of my duramax thermostats. Anyways hasn't lasted more than a couple of years. I would like to find the toyota/denso equivalent.

[datzenmike]

3 minutes ago, Sergio146 said:

Overheating is 1/4 under the H mark

 

I find running normal is about a needle width above half way on the 'run range'. Does it idle at about the half way mark? What do you do to get it to over heat?

[Sergio146]

I ended up changing the thermostat and just on idling alone, I fixed the overheating issue. Prior to changing it, it overheated at idle but now it maintains the temperature sort of where it should be. I would need to drive to fully confirm that there is no overheating though.

[Sephakrid]

That's about where the needle has been on my truck after replacing most of the cooling system (rad, thermostat, water pump, hoses). Intake manifold temperature is stable at around 82C at idle when using an 82C thermostat. I also verified the opening/closing temperature before installing by putting the thermostat in a pot of water and heating it on the stove.

[datzenmike]

You can see a delineated 'run range' on the gauge. All Datsuns I have owned run just a hair above half.

 

The overheating is probably the old thermostat opening correctly to start but failing to open all the way as it should. If curious you could boil it and see.