Overheating

[CBK Lucifer]

I recently installed a Weber on my 620 and it ran fantastic. Drove about an hour afterwards with no issues. I went to go start it up for work the next morning and as soon as I took off the heat spiked just below overheating. I shut it off hoping it’d cool down and it continues to do it. Also, after I shut it off it chugs a ridiculous amount before everything actualy calms down. If anyone has any idea on what’s wrong with it please let me know. I have to get this running before the work week starts

[datzenmike]

On the face of it a carb change shouldn't cause this so it's maybe something you did when changing it.

 

How long did it take to overheat? Like 5 min? 10.... 20??

 

I would call starting to over heat about 3/4 up the temp gauge. Where does it normally run?

 

 

 

 

 

 

[CBK Lucifer]

It takes about 5 minutes to over heat. It normally runs about a 1/4 up the temp gauge

[datzenmike]

The engine can't start up cold and over heat in 5 min. Is the coolant low in the rad?

 

Regardless, the temp should be about the middle of the run range, maybe a needle width higher. I would replace the thermostat. Get a $10 one not the WallMart $2.99 POS. Try that and we'll go from there knowing it isn't the thermostat. 

 

Coolant topped up? Was it low?

[CBK Lucifer]

No I’m alwasys ontop of my fluids. My radiator was full. Brand new radiator and the thermostat is about a month or two old

[DanielC]

I'd change the thermostat.

If your engine starts to overheat, turn on the heater to max heat.  If you do not get heat out of the heater, the water is already low.

[CBK Lucifer]

My heater core is blown. I haven’t been able to get heat since I bought it about 4 months ago

[datzenmike]

The shut off valve may be closed. The cable may be off. Its on the pass side near the floor.

 

The flap door may be set to outside air. Again adjustment ot cable off.

 

Find the outlet from the side of the head near the #4 spark plug. Does it loop around to the lower rad hose or go into the firewall? If the two hoses are joined together in a by-pass the core may be leaking.

 

The core itself may may be plugged with sediment.

[Crashtd420]

While I agree with what the others are saying to look at, Is it also possible the temp sending unit went bad?

 

Other than the gauge on the dash telling you are you sure it's over heating?

Do you have a ir temp gun or a second gauge to verify the temp?

Or even a spare temp sender to try....

5 minutes seems awfully quick to over heat..... 

 

 

 

 

[datzenmike]

 Just like "what is truth".... what is 'overheated'. Normal operating temp on a Datsun is about half way up the run range with a 185F thermostat, (+-a needle width) not necessarily half way up the gauge. All the Datsuns I have ever had ran there, when thoroughly warmed up. I would say that if  it starts running @ 3/4s you are still in the run range but this would indicate that something is changed/happening and keep an eye on it.  

 

15 hours ago, CBK Lucifer said:

I recently installed a Weber on my 620 and it ran fantastic. Drove about an hour afterwards with no issues. I went to go start it up for work the next morning and as soon as I took off the heat spiked just below overheating. I shut it off hoping it’d cool down and it continues to do it. Also, after I shut it off it chugs a ridiculous amount before everything actualy calms down. If anyone has any idea on what’s wrong with it please let me know. I have to get this running before the work week starts

 

The chugging is 'run on' or dieseling a good sign of over heating. 

 

Replace the thermostat. New is no guarantee that it works. In fact new is a red flag.